Final Report Summary - ARAMACC (Annually-resolved archives of marine climate change - development of molluscan sclerochronology for marine environmental monitoring and climatology)
1. Executive summary
The limited coverage (in time and space) of instrumental measurements constrains our understanding of marine change; indeed, the only way in which we can extend the range of real world data is by the use of proxy measurements embedded in natural archives.
The proxy archives contained in marine bivalve shells are one powerful way in which we can do this. These archives are unique in that they are periodically (usually annually) resolved, replicable, and specific to the marine realm. Their study has given rise to a new scientific field (molluscan sclerochronology) and the development and consolidation of this field has been the aim of the multi-partner Marie Curie ITN reported here (ARAMACC: “Annually Resolved Archives of Marine Climate Change”).
In summary, twelve fellows (ten ESRs and two ERs) based at eight partners worked on eleven distinct subprojects. In the spirit of ITNs, the fellows were provided with a diverse training programme that addressed all aspects of the field of sclerochronology. The ARAMACC fellows were recruited from a range of countries (China, Germany(3), Greece, Italy, Russia, Spain(2), Sweden, UK, USA), and the gender split was 8 female to 4 male.
All ten ESRs completed their three-year contracts and successfully completed their research programmes. Five of them also completed their PhDs before the end of their contracts or shortly afterwards, while the other five are in the process of writing up. Four of the ESRs have either started or been offered postdoc positions. Seventeen peer reviewed articles have been published or accepted and a further nine have been submitted.
All the generic and specialist training was delivered as described in the original proposal, including two research cruises that also provided training in carrying out science at sea. With just two exceptions there was 100% attendance by all Fellows at the training events. The training events were fully open and thirteen spaces at the various training events were taken by participants from outside ARAMACC.
Among the major science achievements were: (i) the development of new proxies for ambient temperatures based on shell crystal fabrics; (ii) new and detailed findings on the incorporation of trace elements into the shell; (iii) detailed work on valve gape and feeding activity by clams; (iv) the resolution of an outstanding species identification issue for the Adriatic Sea; and (v) significant development of the potential of the bivalve proxies for model data assimilation. In all, six new absolutely-dated multicentennial or multidecadal chronologies, anchored to the present day, were developed for the Faroe Islands (east and west), Viking Bank and Fladen Ground in the northern North Sea, the isolated Scottish Hebridean island of St Kilda, and the Bay of Brest in France. In addition, two floating chronologies for a period approximately 3,500 yrs BP were developed for St Kilda and verified by radiocarbon dating.
Dedicated ARAMACC sessions, convened by the ARAMACC fellows, took place at European Geophysical Union (EGU) conferences in 2015 and 2017. These attracted around 30 abstracts, most from people outside the ARAMACC consortium, and filled one (in 2015) and two (in 2017) oral sessions respectively, with the 2017 sessions being particularly well attended, and including some prominent palaeoclimate scientists. ARAMACC was also well represented at the Arctic Frontiers (AF) conference in Tromsø in January 2017, with the final ARAMACC training event being integrated into the AF Young Scientists Forum.
ARAMACC was strongly represented at several other major international conferences, and, in particular, ARAMACC participants made a very strong contribution to the 4th International Sclerochronology Conference, held in Portland, Maine, USA in June 2016. This contribution was likely decisive to the success of the conference, and perhaps even to the short-term cohesion of the whole field of sclerochronology.
2. Project context and objectives
The context of ARAMACC is the ability to use environmental proxies in the shells of marine bivalve molluscs as monitors of past marine conditions. These shells contain periodic (usually annual) banding, which enables each part of the shell to be precisely and accurately dated. In addition, some species are very long-lived and grow synchronously within populations, so that dead shell material can be dated (“crossdating”) by comparing their banding patterns with similar patterns in live-collected shells. Essentially, these bivalves function as a marine equivalent of the terrestrial tree-ring archive, providing proxy measurements of environmental variables at annual and subannual resolutions. The ability to crossdate banding patterns enables the creation of chronologies from multiple shells (so that proxy measurements can be replicated), and these chronologies can extend back in time for centuries or even millennia before the onset of the industrial age. By analogy with the equivalent scientific field in tree-ring research (“dendrochronology”) this new field is known as “sclerochronology”
Before the development of the ARAMACC proposal, the field had advanced incrementall, through a few individual projects. These indicated the potential of molluscan sclerochronology, but inevitably none of them was able by itself to address the full range of associated disciplines.
For any environmental proxy to be effective, it is necessary to understand the mechanisms linking the ambient environment to one or more proxy measurements. These mechanisms may be physical, chemical or biological, and they include the biological drivers of shell growth, the chemical and kinetic processes that drive isotopic fractionation and the uptake of trace elements in the shell carbonate, and the processes that determine variation in the crystal structure.
It is also necessary to identify and develop applications of the proxy; these include the development of long term proxy-based baseline measurements (ie environmental reconstructions) for use in the commercial and regulatory sectors, and the use of the proxy data for model verification and data assimilation.
Broadly, the ARAMACC objectives were split into science (work packages 1-4) and training (work packages 5-6) WPs.
ARAMACC science
The objectives of ARAMACC science were to address (1) the construction of a network of shell-based chronologies for the climatically important NE Atlantic region; (2) the use of data from these and other existing chronologies for multicentennial model comparisons and to constrain model predictions on decadal timescales; (3) the ecological and biological drivers of calcification rate and increment formation; (4) the development of novel proxies using the geochemistry and crystal structure of the shell material; (5) the use of sclerochronological techniques to produce baseline environmental data for the commercial and regulatory sectors and the promotion of these techniques to the appropriate organisations; and (6) to establish a public data bank of all sclerochronological data (with metadata) from the North Atlantic realm. These objectives are described in more detail below:
(1) The construction of a network of shell-based chronologies for the climatically important NE Atlantic region (WP1).
The initial objectives were:
(a) to build a network of shell-based chronologies (ie proxy archives) for the NE Atlantic region along a transect along the axis of the North Atlantic Current, the main goal being to reconstruct the hydrographic variability of the meridional overturning circulation in the North Atlantic during the Holocene, in particular over the past 1000 years, and to assess the role of the oceanic system in key climate transitions;
(b) where curated shell material was not already available, to collect new material during shell collection campaigns at sea;
(c) once the chronologies were built, to sample the dated material for targeted geochemical (stable isotope and trace element) analyses in order to reconstruct (a) annual to decadal variability through key climate transitions and (b) seasonal variability during distinct climatic states;
(d) to deliver the proxy data to external users in the climate modelling community for incorporation into numerical models of the climate system.
(2) The use of data from these and other existing marine chronologies for multicentennial model comparisons and to constrain model predictions on decadal timescales (WP2).
The initial objectives were:
(a) to develop the use of shell-based proxy records as a tool for model analysis of the amplitude and structure of decadal and multidecadal climate variability in the North Atlantic region;
(b) to constrain the characteristics of model simulated variability, so that the model processes that drive similarities or discrepancies with the real-world data can be identified, thus enabling more realistic model analyses of ocean-atmosphere coupling on these time scales;
(c) To analyze the successful simulations in more detail with the aim of identifying predictors at decadal timescales that can be verified in the proxy records and, in a more limited time frame, in recent instrumental measurements.
(3) The ecological and biological drivers of calcification rate and increment formation (WP3).
The initial objectives were to identify ecological, biological and behavioural drivers that:
(a) precipitate the annual cessation of growth and the formation of the growth check;
(b) affect the seasonal variation in calcification rate;
(c) control longevity;
(d) generate variability in individual responses to the common environmental signal.
These drivers and responses were to be investigated for multiple species using known techniques, including shell marking, gape monitoring and within-increment geochemical analysis.
(4) The development of novel proxies using the geochemistry and crystal structure of the shell material (WP4 part 1).
The initial objectives were:
(a) using controlled growth experiments, to analyze in what proportion, relative to ambient water (and the extrapallial fluids if possible), trace elements are incorporated in shells of cultured and naturally occurring bivalves from different settings;
(b) to develop a model of crystal fabric structures based on the observed patterns and develop an image processing tool for the automated mapping and quantification of crystal fabrics.
(5) The use of sclerochronological techniques to produce baseline environmental data for the commercial and regulatory sectors and the promotion of these techniques to the appropriate organisations (WP4 part 2).
The initial objectives were:
(a) to develop the use of sclerochronological techniques as a monitoring tool of use to the commercial and regulatory sectors;
(b) to use the temporal extent of the chronologies to produce long term baseline data for use in the commercial and regulatory sectors;
(c) to interface between the commercial and academic sectors to maximize the potential commercial exploitation of long-lived bivalves in environmental monitoring by identifying new sampling strategies, identifying new species for sclerochronological analysis and identifying opportunities to apply crossdating and geochemical techniques in existing and ongoing environmental contracts;
(d) in collaboration with the commercial and regulatory sectors, to initiate the development of protocols for the routine incorporation of shell series into environmental monitoring and the exploitation of commercial sampling for climate change applications.
(6) The establishment of a public data bank of all sclerochronological data (with metadata) from the North Atlantic realm (WPs 1, 3, 4).
The primary objective was to ensure that all data produced during ARAMACC was appropriately warehoused.
ARAMACC training
The overall objective of ARAMACC training was to develop a cadre of highly-trained scientists with a range of overlapping and cross-disciplinary skills who are fully committed to the use of high-resolution shell-based archives to increase scientific understanding of the part played by the oceans in the Earth’s complex climate system. With this background, they will be able to apply their skills to the study of past and future climate change and to the goal of ensuring that the use of the shelf seas for infrastructure projects is genuinely sustainable and fully informed. In the process, the competitiveness of European climate science and the commercial value of sclerochronological techniques will be enhanced, together with the geographical mobility and cross-disciplinary range of individual researchers. ARAMACC training had two main complementary objectives, described in detail below:
(1) To provide training in generic and transferable skills (WP5).
The objective of WP5 was to provide a full programme of generic and transferable skills training was provided, specifically including:
(a) research management;
(b) scientific writing and publication;
(c) attracting funding;
(d) entrepreneurship and commercial exploitation;
(e) career development;
(f) dissemination, communication and public outreach
(2) To provide training in scientific skills specific to the field of sclerochronology (WP6).
The objective of WP6 was to provide a full programme of scientific skills specific to the field of sclerochronology, including:
(a) techniques for research at sea;
(b) chronology construction using growth increments in shells;
(c) geochemical techniques in sclerochronology;
(d) ecology of long-lived bivalves;
(e) sclerochronology and numerical modelling ;
3. Main science & training results
ARAMACC Science (work packages 1-4)
ARAMACC science consisted of ten subprojects carried out by ESRs and one project carried out by an ER, divided into four work packages (WPs) and based at eight beneficiaries
WP 1 - The construction of a network of shell-based chronologies for the climatically important NE Atlantic region
WP 1 consisted of five projects, each led by one ESR, and was based at three beneficiaries:
ESR 1.1 Fabian Bonitz, based at UniRes Bergen.
ESR 1.2 Tamara Trofimova, based at UniRes Bergen.
ESR 1.3 Stella Alexandroff, based at SOS Bangor.
ESR 1.4 Amy Featherstone, based at UBO Plouzané.
ESR 1.5 Juan Estrella-Martínez, based at SOS Bangor.
ESR 1.1 Fabian Bonitz: “Variability of Atlantic inflow using sclerochronology (1): Faroe inflow branch” (beneficiary UniRes Bergen)
The aim of this project was the investigation of natural climate variability in the northern North Atlantic over the past few hundred years using natural archives in the shells of Arctica islandica from the Faroes Shelf. Shells were collected during a cruise of the Norwegian research vessel G.O.Sars during November 8th-17th 2014. Annual banding in the shells was used to build a statistically robust multi-centennial master chronology covering the time period AD 1642-2013. The shell growth index of this chronology was found to be strongly positively correlated with phytoplankton dynamics from the Faroese region, so that higher (lower) phytoplankton concentrations are associated with wider (narrower) growth increments. This relationship can be observed on both inter-annual and multi-decadal timescales, allowing the shell growth index to be used as a tool to identify periods/years with increased or decreased phytoplankton concentrations. In the Faroese region, where phytoplankton dynamics are strongly connected to higher trophic levels (e.g. fish stocks), such information for periods before the availability of instrumental observations can be used to estimate historical changes in stocks of commercially important marine resources, such as cod and herring.
Geochemical analysis of the 13C composition of the shell carbonate through time revealed that evidence of the oceanic Suess effect (ie the increase in the ratio of 12C to 13C in the environment that results from anthropogenic emissions of carbon derived from fossil fuels) is preserved in the shell carbonate. In this region, the onset of the oceanic Suess effect seems to occur in the latter half of the 19th century. This is an important finding, since the regional partitioning of the uptake of anthropogenic CO2 by the oceans, and its history, are key factors in the study of the mechanisms by which the global ocean acts as a sink for excess atmospheric CO2. This knowledge will in turn help researchers and climate modellers to assess future changes in the ability of the oceans to act as a buffer for CO2 emissions. The results from this geochemical analysis therefore constitute an incremental step towards this crucial goal.
Geochemical analysis of the 18O composition of the shell carbonate was used to obtain a water temperature record with annual and subannual resolution. The extension of this record to periods before the start of instrumental observations and before the period of major human impacts will help to provide a baseline for the objective evaluation of the impacts of anthropogenic climate change in the Faroese region.
ESR 1.2 Tamara Trofimova: “Variability of Atlantic inflow using sclerochronology (2): northern Norway” (beneficiary UniRes Bergen).
The original aim of this project was the investigation of natural climate variability in the far northern North Atlantic over the past few hundred years using natural archives in the shells of Arctica islandica from the northwest and northern coasts of Norway. Initial campaigns indicated that it would be difficult to obtain sufficient amounts of shell material from these sites, so the focus of the project was shifted further south to a site on the Viking Bank in the northern part of the North Sea. Shells were collected from a depth of about 100 metres during the same G.O.Sars cruise that provided material for ESR1.1. Annual banding in the shells was used to build a statistically robust 265-year long master chronology.
Seasonally and annually resolved geochemical samples (stable oxygen and carbon isotope measurements) were obtained from shells that had been included the same master chronology. These records together provide new insights into the hydrographical variability of the North Atlantic current, in particular into temperature variability and the marine 13C Suess effect.
Shells that had been radiometrically dated to 9600-9335 cal. yr BP were used to build a 240- year long record of shell growth from the early Holocene, providing new data on the decadal scale variability of shell growth at this time. Geochemical analysis of this material has been used to build a 22-year seasonally-resolved oxygen isotope record, providing an indication of the seasonal variability of bottom water temperature on the Viking Bank during the early Holocene. This research has also contributed new independent data related to sea-level changes on the Viking Bank.
A proxy improvement study was carried out in collaboration with ARAMACC beneficiary JGU Mainz to assess the possible influence of crystal habits on the stable isotopic composition of shells and hence their potential effect on paleoclimate reconstructions. This part of the research is important for the interpretation of oxygen isotope paleothermometry.
ESR 1.3 Stella Alexandroff: “Variability of Atlantic inflow using sclerochronology (3): Scotland-Norway branch of the North Atlantic Current” (beneficiary SOS Bangor).
The aim of this project was the investigation of natural climate variability in the Scotland-Norway branch of the North Atlantic Current over the past few hundred years using natural archives in the shells of Arctica islandica from waters off the west coast of Scotland. Shells were collected during a cruise of the SOS Bangor research vessel Prince Madog during May 27th – June 3rd 2014. The cruise was planned and co-organized by the ESR.
Two floating chronologies and one modern chronology have been constructed using shells from St Kilda, an island group situated on the western Scottish shelf about 70km off the Outer Hebrides and strongly influenced by oceanic conditions. Both floating chronologies were constructed using shells from Glycymeris glycymeris that lived approximately 3500 years ago (determined by radiocarbon dating). Each chronology (consisting of seven and two shells respectively) spans approx. 200 years. The modern chronology, spanning 131 years (AD 1885-2015), was built using Arctica islandica shells recovered by divers from the same location. Shells from live collected specimens of G. glycymeris were also used for geochemical analysis, but these shells were not positioned in a chronology as they were very short-lived (with lifetimes of the order of 12-20 years)
Average growth in the modern chronology shows significant correlations with North Atlantic sea surface temperatures (SSTs) since 1981 and with North Atlantic sea surface salinity since 1900.
Radiocarbon dating of the shells in the floating chronologies was consistent with the relative dating indicated by crossmatching, thus confirming the reliability of both techniques.
Sub-annually resolved oxygen isotope samples were taken from: (1) shells from one of the floating G. glycymeris chronologies, (2) shells from the modern A. islandica chronology and (3) live collected G.glycymeris. The stable oxygen isotope ratios (δ18O) in the modern shells (both species) converted to regional instrumental sea surface temperatures (SSTs) using standard palaeotemperature equations without any need for correction. This finding confirms that shell δ18O is a reliable proxy for SST in both species at this location and that it can be used for reconstructions of SST. Comparison of δ18O in the fossil G. glycymeris with that in the modern G. glycymeris demonstrates that (1) the seasonal range of SST was considerably higher in the 4th millennium BP, and (2) the annual mean SSTs were cooler than they are today.
ESR 1.4 Amy Featherstone: “Construction of long annually-resolved shell-based chronologies using Glycymeris glycymeris from the Bay of Brest, France” (beneficiary UBO Plouzané)
The main objective of this project was the construction of long annually-resolved chronologies using annual growth increments in the shells of the dog cockle, Glycymeris glycymeris.
The initial goal was to work with specimens collected in NW France, Croatia and Iberia. However, because of the lack of availability of sufficient material in some areas, the geographical extent of the project was eventually restricted to the Bay of Brest, France.
The main research goals of the project did not change, being (i) to build a long annually resolved shell-based growth chronology and relate changes in shell growth over time to environmental variables and climate forcings; (ii) to use stable oxygen isotope geochemistry to reconstruct temperature variations in the Bay of Brest over the past few decades; and (iii) to investigate the potential of trace element concentrations in the shells as proxies for seawater temperature, salinity, phytoplankton dynamics and possibly pollution.
Sampling took place every month at a site close to the outlet of the Bay of Brest, at an average depth of 20 m, between September 2014 and November 2015. In all, several hundred live clams and dead shells were collected by dredging. Soft tissues were removed and kept frozen for subsequent biological analyses. Some tissues were stored in ethanol for genetic analyses (this being a collaboration with IOF Split). The shells were carefully labelled and stored in the lab and made available on request to other partners in the ARAMACC project.
A sub-sample of thirty-eight specimens (twenty live-collected and eighteen dead-collected shells) was selected based on morphometric measurements (on the assumption that the largest and heaviest and longest specimens would also be the longest lived). The shells were processed using standard sclerochronological techniques (embedding in resin, cross-sectioning, polishing and production of acetate peel replicas of the banding in the hinge area). The longest-lived specimen was found to be 70 years old. A shell master chronology spanning 1891 to 2014 was built using standard tools derived from dendrochronology. This chronology is statistically robust (Expressed Population Signal, EPS > 0.85) for the last 40 years, but sample depth is very low before 1975. The position of four of the shells in the chronology was verified by radiocarbon dating. Correlation of the annual growth indices with local environmental factors indicated that the predominant drivers of shell growth were river inflow, salinity and suspended particulate matter.
Geochemical analysis was carried out on a sub-sample of the shells that had been used for chronology building. A total of 24 specimens of different ages were analysed for the stable oxygen isotope ratios (δ18O) in their shell, with sampling restricted to the ontogenetically youngest portions of these specimens so that the seasonal cycle could be observed. The samples were run by the ESR during a secondment at JGU Mainz. The main results show that variations in shell δ18O accurately record local sea surface temperatures, allowing the creation of a 45-year SST reconstruction for the Bay of Brest (1966-2010). Correlations between this and climate forcings indicate that SST variations in this area may be partly controlled by the strength of the subpolar gyre and the East Atlantic Pattern.
In addition, five shells (three under the age of 10 and two aged 45) were analysed using an LA-ICP-MS system to determine the elemental composition of the shell aragonite (magnesium, strontium, barium, manganese, boron, lead, uranium, and calcium). These results were obtained quite late during the PhD project and further analysis will be required before they can be interpreted as proxies for environmental variables.
Overall, this study confirms the potential of G. glycymeris as an archive of climatic and environmental variability in the Bay of Brest. As there are a large number of sub-fossil specimens in the area, there is good potential to extend the chronology further back in time.
ESR 1.5 Juan Estrella-Martínez: “Holocene climate variability in UK waters based on Arctica islandica sclerochronology” (beneficiary SOS Bangor)
The initial aim of this project was the investigation of natural climate variability in UK waters (specifically the Irish Sea and North Sea) during the Holocene using natural archives in the shells of Arctica islandica. As all the required shells were already in curated collections held at SOS Bangor and NIOZ Texel, no shell collection campaign was required. Time constraints resulted in the Irish Sea shells being removed from the remit of the project, which has concentrated on material from the Fladen Ground, northern North Sea held in the collection at SOS Bangor.
This project consisted of two major subprojects: (1) The extension of the Fladen Ground A. islandica chronology to AD 1551; (2) an early Holocene floating chronology that is thought to cover the 8.2Ka cold event.
1. The extension of the Fladen Ground A. islandica chronology to AD 1551.
An existing published chronology for the Fladen Ground, northern North Sea (Butler et al., 2009) extends back to AD 1870. In this subproject, the chronology was extended back to AD 1551 with the addition of more shells from the SOS Bangor collection. A temperature equation for shell 18O was developed by calibrating subannual samples to measured bottom water temperatures (BWT) from the same geographical area. The calibration indicated that the growing season for A. islandica in the Fladen Ground is March-August. The temperature equation was used to reconstruct mean March-August BWTs for the 454 years AD 1551-2004. While more analysis of this time series is required (and is currently underway), there are indications of a dynamical link between the reconstructed BWTs and the Scandinavian Pattern that is most evident following large tropical volcanic eruptions. Spatial correlations between the reconstructed BWTs and measured sea surface temperatures show a clear stratification signal, with the timing of stratification appearing to be linked to the strength and sign of the spring summer NAO index.
2. An early Holocene floating chronology that is thought to cover the 8.2Ka cold event
A 200-year floating chronology, containing three fossil shells from the Fladen Ground, was constructed. Radiometric dating of the three shells (incorporating the global modelled marine reservoir correction) indicated a date in the early Holocene around 8,300 years BP (where present = AD 1950). Stable oxygen isotope measurements showed a marked increase in the 18O ratio (corresponding to colder bottom water temperatures if the 18O of the seawater is assumed constant) during a 55-year period in the middle of the chronology. On the basis of the radiometric dating, this 55-year period is offset from the 50-year cold period that marks the so-called “8.2Ka cold event” in the Greenland ice cores by about 141 years. If the two isotope excursions are in fact contemporaneous, this would indicate a local reservoir correction (R) of -141 years suggesting greater ventilation of North Sea waters during the early Holocene, consistent with shallower waters at the time.
WP 2 – Integration of sclerochronological data from multiple sites into numerical models
WP2 constituted the climate modelling part of the ARAMACC project. The goal of this part of the project was to develop optimum methods to integrate the network of shell-based chronologies developed in WP1 with the current generation of climate models. WP2 consisted of a single subproject.
ESR 2.1 Maria Pyrina: “The use of proxy data from molluscan sclerochronology for model comparison and decadal prediction“ (beneficiary HZG Geesthacht)
The technical aim was to analyze the amplitude and spatial structure of decadal and multi-decadal climate variability in the North Atlantic region by combining the output of climate model simulations with proxy-based reconstructions of past climate. While proxy data from single Arctica islandica populations has previously been used to reconstruct local climate, no bivalve proxy has so far been used for the reconstruction of large scale climate patterns in the North Atlantic basin. The project was developed around five principle research questions:
1. Does A. islandica have the potential to be used in climate field reconstructions (CFRs) of North Atlantic SSTs?
2. If there is a North Atlantic basin signal registered at sites occupied by A. islandica populations, which CMIP5 models best reproduce that signal?
3. Which climate reconstruction techniques are best suited for the reconstruction of SSTs based on records from A. islandica?
4. Is the climate model method or the statistical reconstruction method more important for the evaluation of the skill of the reconstruction?
5. Do changes in solar forcing affect summer upper ocean circulation?
In order to use proxy records from A. islandica in CFRs of the North Atlantic climate, it was first necessary to investigate the co-variability of these records in the North Atlantic. In a second step, aiming to combine the local information provided by A. islandica into the broader context of large scale climate patterns, different statistical methods were assessed using controlled pseudoproxy experiments (PPEs). As it is a prerequisite for the construction of a meaningful PPE that the climate model is able to represent realistic spatiotemporal characteristics of the observed climate, the climate models used as the basis of the PPEs were evaluated for their ability to simulate North Atlantic spatiotemporal climate variability.
A very significant outcome of WP2 was the finding that the sites occupied by A. islandica populations in the northeast Atlantic constitute an effective network for the reconstruction of large scale climate in the northeast Atlantic basin. In addition, the assessment of various statistical methods that can be applied to climate field reconstructions based on the A. islandica network found that both Principal Component Regression and Canonical Correlation Analysis can be used for the reconstruction of large scale climate based on the comparatively sparse A. islandica network (the assessment of statistical methods is an important methodological step, as the quality of past climate reconstructions largely depends on the statistical method applied.) In addition, it was found that only a subset of current state-of-the-art models are appropriate as realistic test beds, and that the model used affects the skill of the climate field reconstruction more than the statistical method applied.
In addition to these assessments of climate reconstructions for the North Atlantic basin, and in order to obtain a better understanding of the impact of changes in external forcings, the drivers of North Atlantic sea surface temperature variability during the preindustrial era of last millennium were investigated. The results of this test indicated that phases with lower solar activity might be linked to blocking-like atmospheric circulation in the North Atlantic basin.
WP 3 – Ecological and biological drivers of calcification rate and increment formation
The fundamental scientific aim of WP 3 was to better understand the environmental factors that control increment variability in long-lived marine bivalve molluscs and consequently to develop tools to improve the interpretation of palaeo-environmental reconstructions based on growth increment series derived from these species.
WP 3 consisted of two projects, each led by one ESR, and based at two beneficiaries:
ESR 3.1 Irene Ballesta Artero, based at NIOZ Texel.
ESR 3.2 Ariadna Purrot Albet, based at IOF Split.
ESR 3.1 Irene Ballesta Artero : “Ecological and biological drivers of calcification rate and increment formation” (beneficiary NIOZ Texel)
This work can be subdivided into three subprojects:
1. The in situ study of animal behaviour in relation to seasonal and environmental variability. This is being addressed during experimental work in northern Norway where in situ monitoring of the valve gape behaviour of Arctica islandica has been ongoing since the start of the project. The results to date show that in a natural setting the presence of food is the most important driver of gaping activity. As a result of this work, the ESR has collaborated with a research group working on similar topics at the Institute of Environment and Marine Science Research (IMEDMAR) in Spain.
2. The laboratory-based study of the interacting influences of temperature and food availability on shell growth. This was addressed during an extensive laboratory-based growth experiment over a three-month period during which the interacting influences of temperature and food supply on behaviour and growth were studied. The data have been analyzed and the resulting manuscript (“Interactive effects of temperature and feeding conditions on the growth of Arctica islandica juveniles”) will be submitted shortly. The geochemistry of these experimentally grown shells are being used for chemical analyses of the carbonate composition in cooperation with the ARAMACC partner at JGU Mainz.
3. The analysis of energy budgets devoted to reproduction and growth increment formation, and the construction of a dynamic energy budget model from which growth, food or temperature conditions can potentially be derived. This subproject has been addressed through the organization (by the ESR in collaboration with a local fisherman in Norway) of the collection of monthly shell samples for the analysis of reproductive state and condition. These samples form the basic data for the development of a DEB (Dynamic Energy Budget) model for A. islandica. To obtain the skills required for the construction of a DEB model, the ESR joined a two-week symposium which included skills exchange with all the major experts in this field.
Both experimental and in situ experiments have shown that food supply is a major driver of A. islandica shell growth in Arctic conditions. These experimental results can be used to refine and improve the use of A. islandica as an archive for palaeoceanographic reconstruction, and further enhancement, including model integration, will be made possible with the development of a DEB model for A. islandica.
ESR 3.2 Ariadna Purroy Albet: “The ecological and biological drivers of calcification rate and increment formation in Glycymeris spp.” (beneficiary IOF Split).
All the practical experiments in this project were undertaken in situ, beginning in May 2014 and continuing until October 2015. The ESR conducted monthly field sampling at three locations in the eastern Adriatic Sea (Pag Bay, Cetina river estuary and Pašman channel). The target species were Glycymeris bimaculata, Glycymeris pilosa (initially thought to be Glycymeris glycymeris) and Callista chione. In addition to the bivalve samples, samples from the water column and sediment were also collected. Laboratory analysis started in parallel with the field sample collection and included measurement of the gonadosomatic index, histological analysis of the gonads, and analysis of stable isotopes and fatty acids in bivalve digestive gland and potential food sources. Geochemical analysis of soft tissue (stable isotopes of nitrogen and carbon) and shell material (stable isotopes of oxygen and carbon) was carried out at the ARAMACC partner at JGU Mainz. The analysis of the shell material was undertaken by the ESR on secondment at JGU Mainz.
The results of this work clearly indicate spatial and temporal variations in environmental characteristics and trophic ecology of the target species. The best food quality in the particulate matter was observed during spring and summer and food resource partitioning was observed between C. chione and G. bimaculata. Inter-site variations in the spawning timing and duration of C. chione were likely associated with temperature whereas in Glycymeris spp. spawning did not seem to be not directly connected to temperature. Shell growth in Glycymeris spp. took place between May and December indicating that temperature is an important determinant of shell growth. The results indicate that the growth season is limited by food availability.
This work has significantly contributed to the development of bivalve sclerochronology research in the Adriatic and Mediterranean Seas by developing a detailed characterization of the target species in relation to their environment. It indicates the value of coupling sclerochronology to ecological studies for a better understanding of species life-history traits. Important results were obtained relating to the ecology of the long lived bivalves G. bimaculata and G. pilosa, and to the ecology of the commercially important species C. chione. These results have potential for application in management and protection of natural populations of C. chione and provide a better understanding of the trophic ecology and reproductive processes of the studied species.
Ariadna Purroy collaborated with other ARAMACC ESRs including Liqiang Zao and Stefania Milano (ESR4.2 and ESR 4.3 based at JGU Mainz) and Amy Featherstone (ESR1.4 based at UBO Plouzané). These collaborations resulted in joint manuscripts which have been published, are under review or in preparation.
WP 4 (part 1) – Novel applications and proxy development
WP 4 part 1 focused on the formation mechanisms and interpretation of geochemical and crystallographic proxy data fund in the shell material. The fundamental science aim was to generate novel proxies for the reconstruction of key environmental variables.
WP 4 part 1 consisted of two projects led by two ESRs and based at a single beneficiary:
ESR 4.2 Liqiang Zhao, based at JGU Mainz.
ESR 4.3 Stefania Milano, based at JGU Mainz.
ESR 4.2 Liqiang Zhao: “Trace element incorporation into shells” (beneficiary JGU Mainz)
The primary goal of this project was to evaluate the extent to which the trace and minor element chemistry of bivalve shells can be employed as a tool for the reconstruction of environmental variables. Bivalves closely control the amount and type of trace and minor elements that are incorporated into the shells, although this can result in the modification of their microstructure and consequently negatively affect the mechanical properties of the shells. As a result, the element levels in the shells typically remain far below those in the ambient environment and far below those of synthetic precipitates of CaCO3.
To address these issues, the ESR conducted a series of controlled tank experiments with living bivalves during which selected environmental parameters were modified. After the end of each experiment, the chemistry of the shell portion that formed during the experimental phase was investigated and compared to the respective growth conditions. To identify the mechanisms by which the different ions are transported from the water to the site of shell formation, the ESR also added substances to the tank water that blocked the activity of certain enzymes and ion channels of the mantle epithelium, i.e. active and passive transport mechanisms.
These studies clearly demonstrate that the trace and minor elements of the studied bivalve shells recorded environmental conditions. Findings have been presented at various international conferences and reported in five papers that were published in international peer-reviewed scientific journals. The main outcomes are briefly reported below.
Because the incorporation of elements into minerals is in part driven by thermodynamic fractionation effects, the trace and minor element content of a mineral can potentially reflect environmental conditions during mineral formation. In living organisms, the elements in the water must pass through semipermeable membranes (in bivalves: the mantle epithelia) to reach the site of hard part formation. In bivalves, this is accomplished by enzyme-mediated carriers such as Ca2+-ATPase, through Ca2+ channels, and by passive diffusion through ion channels. Elements that can freely (passively) move across semipermeable membranes are considered more suitable for environmental reconstructions, because their concentration in the extrapallial space reflects that of the ambient water. The other two mechanisms require energy and are thus biologically controlled.
To identify the mechanisms by which selected elements are transported across epithelial membranes, the ESR used Corbicula fluminea as a model organism. This bivalve tolerates a wide range of temperature (0-43°C) and salinity regimes (up to 24 PSU). Results may thus be applicable to both freshwater and marine ecosystems. The ESR first deactivated the Ca2+-ATPase enzyme with Ruthenium Red and then blocked Ca2+ ion channels with lanthanum and Verapamil. As a result, the concentrations of manganese, copper and lead in the shells of this species decreased, but magnesium, strontium and barium levels remained unchanged. These findings suggest that Sr, Mg and Ba of shells of the studied species can potentially serve as proxies of environmental conditions (Zhao et al. 2017a).
A subsequent experiment (Zhao et al. 2017b) investigated an aspect of bivalve sclerochronology that has been controversially debated for a long time, i.e. whether strontium and barium can be used as proxies of water temperature and primary productivity respectively. The results indicate that, while C. fluminea closely tracks changes of the Sr and Ba content of the ambient water, the distribution coefficients of both elements were lower than expected for equilibrium precipitation. For example, the concentration of Sr in the shells is four times lower than it is in the ambient water and the extrapallial fluid, suggesting that another biological mechanism controls the transport of ions into the shells; this might be a macromolecular ion selection at the calcifying front. In spite of that complication, increasing ambient water temperatures were faithfully recorded as decreasing Sr/Ca ratios in the shells. In conclusion, as long as Sr levels in the water remain constant, the Sr/Ca ratio of the shells provides a reliable tool for reconstruction of past water temperature.
Interpreting the Ba/Ca ratios in the shells is less straightforward because they are affected by a combination of phytoplankton abundance, growth rate and temperature. To reconstruct primary productivity changes from Ba/Ca values, ambient temperature and shell growth rate must be known.
The third study (Zhao et al. 2017c) investigated how two selected bivalve species (Mytilus edulis and Patinopecten yessoensis) are affected by ocean acidification and temperature rise (these being two major consequences of present day global change). This study also investigated the possibility of using shell Na/Ca as a proxy for pH. Ocean acidification increases the number of protons in the water and, consequently, in the extrapallial fluids. Some species such as Mytilus edulis are capable of actively removing excess protons from body fluids using Na+/H+ pumps. Since this enzyme exchanges one proton for one sodium ion, sodium levels in body fluids will increase and, potentially, so will those in the shell. Since this active proton removal requires energy, one would expect slower growth rates. This was indeed the case: mytilid specimens exposed to low pH showed higher Na/Ca ratios in the shell and grew more slowly, showing that shell Na/Ca can serve as a proxy for ocean acidification. Patinopecten yessoensis, on the other hand, does not possess a Na+/H+ pump, so that shell Na/Ca ratios and shell growth rate remained unchanged when pH decreased. Temperature rise also had opposite effects on the shells: the mytilid grew faster, the pectinid slower. Anthropogenic climate change thus affects both species, but in different ways, so that P. yessoensis is more resilient to ocean acidification, while M. edulis can better cope with ocean warming.
A subsequent study (Zhao et al. 2017d), investigated epigenetic effects on the tolerance of Ruditapes philippinarum to ocean acidification. Offspring of parents that were already exposed to lower pH could cope better with acidified conditions and grew faster than offspring of parents that lived in neutral seawater. Irrespective of pH levels which the parents experienced, the sodium levels in the shells of the offspring were increased implying active removal of excessive protons through the Na+/H+ exchanger. Furthermore, the offspring of parents that lived in acidified water showed lower shell sodium levels than those of the parents from neutral seawater. These results demonstrated that some species have a capacity to acclimate or adapt to ocean acidification.
The final study (Zhao et al. 2017e) evaluated the use of manganese in shells of Hyriopsis cumingii as an indicator of eutrophication. Results confirmed the hypothesis. Under reducing conditions, Mn is biologically available for the bivalves and can be incorporated into the shells. After phytoplankton blooms, the amount of organic detritus at the seafloor increases and oxygen levels decrease. In turn, this increases the solubility of Mn in the water which is inhaled by the bivalves, resulting in higher Mn levels in the shells. Manganese could be used in future studies aiming to reconstruct pollution histories.
ESR 4.3 Stefania Milano: “Exploring the potential of shell crystal fabrics as novel environmental proxies” (beneficiary JGU Mainz)
The aim of this project was to develop and calibrate new microstructure-based environmental proxies, adding a quantitative element to previous work on the relationship between shell microstructure and temperature, which had been purely descriptive.
For her first study (Milano et al. 2017a), Stefania Milan, selected the short-lived (ca. 6 year-old) common cockle, Cerastoderma edule as target species. For calibration purposes, CTD loggers were deployed in the intertidal zone of the southern North Sea recording temperature and salinity over more than one year on an hourly basis. During the same time interval, water samples were collected nearly every week to determine δ18Owater, element concentration and salinity (to verify CTD data). Chlorophyll a concentrations and turbidity data were obtained from satellite records (MODIS). From the locality where the logger was deployed and water samples were taken, living specimens of C. edule (different age classes) were collected during and at the end of the monitoring phase. In arbitrarily selected specimens, the (crossed-lamellar) microstructure of the outer shell layer between annual growth lines was studied in radial cross-sections, and morphological characteristics, here size and elongation (= dimensionless shape descriptor, ratio between the major and the minor axes) of individual biomineral units were quantified by means of image processing techniques (= semiautomatic particle recognition and measurement). For comparison with the lowest resolved environmental data, measurements were completed in shell portions resembling ca. one week of growth. Within each of these sample regions, the average size and elongation of hundreds of biomineral units was computed and then compared to instrumental data. The studied shell portions were temporally aligned using daily growth patterns. The results showed that the average size (R = 0.80; R2 = 0.64; p < 0.0001) and elongation (R = 0.52; R2 = 0.27; p < 0.0001) of biomineral units of the studied species were significantly positively correlated to ambient water temperature during the growing season, but not to any other measured environmental variable (ie salinity, chlorophyll a level, turbidity or shell growth rate (daily increment width)) (Milano et al. 2017a).
Throughout the lifetime of this fast-growing species, the observed relationship did not change, i.e. the dimensions of the biomineral units were not affected by ontogenetic age-related trends, but were exclusively correlated to water temperature. Based on these data, a transfer function was computed that can be used to reconstruct temperatures from the dimensions of the biomineral units of C. edule with a 1σ precision error of ±1.5°C. The functioning of the new proxy has been successfully tested on specimens from another locality (Milano et al. 2017a). Our findings were recently corroborated by Gilbert et al. (2017 EPSL 460, 281-292) for different species of Atrina and Pinna. Their results demonstrated that the nacre tablet thickness in these (likewise fast-growing, relatively short-lived [< 30 years]) bivalves is also positively correlated to temperature.
There are a number of advantages of this new tool over existing paleothermometers: (i) in the studied microstructures and species, the morphological properties (size, thickness, elongation) of the biomineral units are strongly linked to temperature (also predicted by thermodynamics); (ii) the new temperature proxy can be applied to well-preserved (microstructurally unchanged) fossils even if the original chemical signature has been lost due to diagenetic alteration; (iii) once the image processing software has been trained to recognize the biomineral units, measurements can be carried out quickly.
In the second study (Milano et al. 2016a), Ms Milano evaluated possible effects of ocean acidification on the shell microstructure of C. edule. Specimens were raised at different pH levels, ranging from 900 µatm CO2 (pH 7.8) to 24,400 µatm CO2 (pH 6.4). However, even at the lowest pH, no significant changes to the size or shape of the biomineral units were detected, and growth rates remained invariant. Conversely, a strong correlation was found between biomineral size and mechanical properties of the shells. Shell portions formed during summer had larger biomineral units and fewer organics and were softer than those formed during the cold season (smaller biomineral units, more organics). Compressive stress is apparently largely absorbed by interstitial organic macromolecules.
This research clearly demonstrated that C. edule can cope well with ocean acidification, since neither growth rate nor the mechanical properties of the shells were affected by increased carbon dioxide levels in the water.
In her third study (Milano et al. 2016b), Ms Milano ESR moved into the field of archaeology. She studied the effects of thermal treatment on the shell of the gastropod, Phorcus turbinatus which is frequently found in archaeological shell middens. For this experiment, modern shells were boiled at 100°C and roasted at 300, 500 and 700°C for 20 and 60 min. Whereas boiling did not modify the shell, increasing roasting temperatures gradually deteriorated the shell integrity, changed the mineralogy and shifted the oxygen isotope ratios to lower values. Results of this study are of great value for shell midden research, because new proxies are now available which provide important information on food processing techniques and subsistence strategies of ancient societies. Furthermore, the observed microstructural and chemical changes can be used to infer the degree of diagenetic overprint which a sediment experienced in which shells were embedded.
In her last study (Milano et al. 2017b), Ms Milano studied the effects of temperature and food supply on the crystallographical and microstructural properties as well as the pigment concentration in shells of Arctica islandica. As in the previous studies, she used the scanning electron microscope and image processing techniques to quantify changes of the shell architecture at the nanometer and micrometer-scale. In addition, Ms Milano determined the crystallographic orientation of the biomineral units and the pigment concentration using confocal Raman spectroscopy. This research showed that neither the microstructure nor the pigment concentration is influenced by food quantity and type. However, temperature changed the crystallographic axes. The next step is to quantify such changes by using electron backscatter diffraction analysis and establish a crystallography-based temperature proxy.
The main ARAMACC supervisor at JGU Mainz, Prof. Dr. Bernd R. Schöne, also published a concise review paper on the use of bivalve shells as biomonitors of heavy metal pollution of aquatic environments in a renowned international peer-reviewed journal. In this article, a special focus is placed on high-resolution, precisely dated records of pollution that can be used to monitor bioavailable contaminants and determine baseline conditions in aquatic environments prior to human perturbation. Both is crucial for successful conservation and environmental restoration efforts.
Reference
Schöne BR and Krause RA 2016. Retrospective environmental biomonitoring – Mussel Watch expanded. Global Planetary Change 144, 228-251.
WP 4 (part 2) – Commercial/regulatory aspects of sclerochronology
WP 4 part 2 focused on exploitation of sclerochronological data in the commercial and regulatory sectors. It consisted of a single project, carried out by two experienced researchers (ERs) and was based at a single beneficiary:
ER 4.1(a) Juliane Steinhardt, based at HAL Aberdeen.
ER 4.1(b) Lars Beierlein, based at HAL Aberdeen.
The first appointment, Juliane Steinhardt, left the position after 13 months for personal reasons, and she was replaced by Lars Beierlein.
WP4 part 2 was focused on the development of the use of sclerochronological techniques as monitoring tools of use to the commercial and regulatory sectors. ER4.1 was to interface between the commercial and academic sectors to maximize the potential commercial exploitation of long-lived bivalves in environmental monitoring by identifying new sampling strategies, identifying new species for sclerochronological analysis and identifying opportunities to apply crossdating and geochemical techniques in existing and ongoing environmental contracts.
Progress in this area is inevitably incremental, and the response by companies to suggestions that they use new techniques tends to be based on consideration of any potential profit. The main task of ER4.1 was to write a report on existing uses of shell material for environmental monitoring and the potential for new techniques that could enhance this application and make it more robust. The principle outcome was a paper and a number of talks at influential conferences including ICES and Arctic Frontiers.
ARAMACC Training (work packages 5 & 6)
ARAMACC training consisted of seven training events (three workshops, two summer schools and two research cruises with a training element).
Summer School #1 (SOS Bangor 16th – 23rd May 2014)
The first ARAMACC training event was held in the sclerochronology department of School of Ocean Sciences at Bangor University. Like all the training events, this summer school consisted of paired modules in generic skills and specialist techniques. The generic skills section introduced the students to principles of research management and included training in: 1) Effective management of personal research activity; 2) Health and Safety; 3) how to maximise benefit from host supervisory teams and from secondments at other partners; 4) research ethics; 5) Intellectual Property Rights (IPR); 6) awareness of the wider scientific context.
The specialist module focused on the fundamental techniques of chronology building using shells: the construction of crossdated chronologies using multiple shell growth increment series. It included training in: 1) Health and Safety issues associated with shell sectioning (including sectioning and use of chemicals); 2) selection of suitable shells for analysis (key metrics, shell condition, preliminary 14C dating); 3) methods of shell preparation (sectioning, grinding, polishing, , embedding in resin, acid etching, acetate peel replicas, thin-sectioning, staining); 4) measurement of annual growth increments using image analysis software; 5) detrending methods (negative exponential, splines, Regional Curve Standardisation); 6) software tools for chronology construction (COFECHA, Shellcorr, Arstan); 7) chronology statistics (eg Expressed Population Signal); 8) statistical techniques for environmental reconstruction using instrumental series (eg calibration-verification).
We were especially pleased to welcome a distinguished visiting researcher, Valerie Trouet, from the Laboratory of Tree-Ring Research at University of Arizona. Professor Trouet demonstrated the strong links between sclerochronology and the established field of tree-ring research, as well as showing the use of KNMI Climate Explorer for analysing proxy-environment links.
Science at sea #1 (Research cruise to the Hebrides and St Kilda with RV Prince Madog) 27th May – 3rd June 2014
The purpose of this cruise was to collect dead and live Glycymeris glycymeris and Arctica islandica from various sites off NW Scotland for use in building shell-based chronologies for ESR1.3 with the ultimate goal of obtaining a multi-centennial record of the variability of the Scotland-Norway branch of the North Atlantic Current (NAC). Shells were collected from Skye, Canna and St Kilda.
Key skills training was provided in: 1) Health and Safety at sea; 2) deployment and operation of oceanographic equipment, geophysical equipment (side-scan sonar) and bottom-sampling equipment (grab samplers, multi-corers, gravity corers, dredges); 3) sample screening and subsample selection; 4) sample preservation and curation techniques; 5) appropriate onboard communication with the scientist-in-charge and other scientists and with the ship’s master, officers and crew; 6) ethical issues associated with the collection of live animals.
Science at sea #2 (Research cruise to the Faroe Islands and Viking Bank with the Norwegian research vessel GO Sars) 8th – 14th November 2014
The purpose of this cruise was to collect dead and live Glycymeris glycymeris and Arctica islandica from sites around the Faroe Islands and the Viking Bank for use in building shell-based chronologies for ESRs1.1 and 1.2 with the ultimate goal of obtaining a multi-centennial record of the variability of Atlantic inflow to the Norwegian Sea. Shells were collected from sites to the southeast and southwest of the Faroe Islands, and from several sites on Viking Bank.
Key skills training reprised that provided during Science at sea #1, although in this case all the ESRs were present on the cruise.
Workshop #1 (Held at JGU Mainz 14th – 20th March 2015)
The fourth training event (and first workshop) was held in the Institute of Geosciences at Johannes Gutenberg Universität in Mainz.
In this case, the generic skills module was devoted to scientific writing and publication, with the aim of providing training in publication options (print and online), journal selection, manuscript preparation and submission, and the peer review system. The students worked from their own manuscripts, preparing them for publication and “reviewing” each others’ manuscripts. Invited speaker Thierry Corrège, Editor-in-Chief at Palaeogeography, Palaeoclimatology, Palaeoecology gave an informed talk on the current world of scientific publishing.
The scientific skills module focused on geochemical techniques used in sclerochronology. Participants brought their own samples and learnt various techniques for shell preparation and analysis. All the fellows were able to obtain practical experience of one or more of the geochemical analysis systems available at the Institute, including Continuous Flow-Isotope Ratio Mass Spectrometry (CF-IRMS), Inductively coupled plasma atomic emission spectroscopy (ICP-OES) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS).
Workshop #2 (Held at NIOZ Texel 26th October – 2nd November 2015)
The fifth training event was held in the Royal Netherlands Institute for Sea Research (NIOZ), situated on the Dutch island of Texel.
This workshop started with the specialist skills section, which was devoted to the ecology of long-lived bivalves. The aim of this module was to provide training in the ecological and biological contexts of growth increment formation. We had talks by Marc Lavaleye from NIOZ on ecological adaptation of bivalves and by Julien Thébault from UBO Plouzané on taxonomy, followed by a practical exercise on bivalve identification. Bryan Black, the visiting scientist from University of Texas at Austin, led a challenging exercise on multivariate analysis in ecology, including the use of sclerochronological datasets in multivariate analysis. As a final treat, Chris Richardson from SOS Bangor led a field exercise, sampling the common cockle Cerastoderma edule from nearby tidal flats. The samples were later eaten at the home of one of the students.
The generic skills part of this workshop concentrated on the funding landscape and how to attract funding. Students were trained in grant and proposal writing, peer-reviewing of grant proposals and delivery of contractual obligations. The main part of the workshop was the writing of proposals to the “Scientific Research Council of Ruritania”, prepared by teams of 3 or 4 students.
As an optional bonus (which most of the students attended), Rob Witbaard organized a two-day workshop in the computer language “R”.
Summer School #2 (Held at IOF Split 8th – 13th May 2016)
The second summer school, and sixth training event altogether, was held in the Institute of Oceanography and Fisheries in Split, Croatia.
The generic skills section of this summer school focused on dissemination, communication and public outreach. Here, participants received training in the range of media that are available for communication of science (including social media and broadcast media), presentation of science at outreach events, oral presentations to general audiences and involvement in legislative and advisory bodies. The school included live practice in interviewing techniques and an entertaining talk by Ana Bedalov, who had organized the Research Night in Split the previous year. Examples of the hazards and delights of working with the media were presented by Michael Carroll, James Scourse and Paul Butler. Thanks to local contacts, news items on the school appeared on Croatian TV and in the local press.
This was followed by the specialist part of the school, which was devoted to the link between sclerochronology and numerical modelling. The aim was to introduce the students to the use of sclerochronological time series as a tool for constraining and validating numerical climate models. This section featured talks by invited speaker Paul Halloran from University of Exeter, and by ARAMACC participants Odd Helge Otterå and Eduardo Zorita. Participants were able to compare their data with model data. Some proxy-model connections were made which, after a bit more analysis, might lead to some interesting results.
Workshop 3 (Held at Akvaplan-niva, Tromsø 24th – 30th January 2017)
The final (seventh) ARAMACC training event took place in Tromsø, northern Norway, and was linked to the Arctic Frontiers (AF) 2017 conference. AF is a transdisciplinary initiative that links research, policy and business in the context of the Arctic Ocean. It holds an annual conference in Tromsø in late January around the time when the sun first appears above the horizon after the long Arctic winter. There were three parts to this event:
1. Before the AF conference sessions, a Retreat Day (24th January) was organized by Michael Carroll. This took place at the Wilderness Centre (Vilmarkssenteret) outside Tromsø and included good food and drink, dogsledding in the snow, and a full day of reflection on the project and discussion of future developments.
2. The final ARAMACC conference was merged into AF 2017, where all the ARAMACC fellows were allocated talks or poster presentations.
3. After the conference, the ARAMACC fellows joined the AF Young Scientists Forum (YSF), which took place on the coastal Hurtigruten cruise and at Svolvær in the Lofoten Islands. The final ARAMACC training module (“Entrepreneurship, commercial exploitation and career development”), was merged into the YSF. This included talks on career development and interviewing techniques (Melita Peharda), the use of scientific data in the context of the oil and gas industries (Geir Morten Skeie), and the links between science and entrepreneurship (K. Tønnesen Busch). In addition, the YSF included a wide range of talks on cultural matters relating to the Arctic, as well as ARAMACC-led talks on sclerochronology from northern Norway (Al Wanamaker) and on Holocene marine climate reconstructions (Carin Andersson Dahl).
4. PhDs and postdocs
ESR 1.1 Fabian Bonitz PhD defence expected in spring 2018.
ESR 1.2 Tamara Trofimova PhD defence expected in spring 2018.
ESR 1.3 Stella Alexandroff PhD defence expected in summer 2018.
ESR 1.4 Amy Featherstone defended her PhD (successfully, subject to satisfactory revisions) on June 29th 2017. She has subsequently accepted a 10-month position at Åarhus University, Denmark, which began in October 2017. She plans to apply for Marie Curie postdoctoral funding to continue her work in Åarhus after the position finishes.
ESR 1.5 Juan Estrella-Martìnez PhD defence expected in summer 2018.
ESR 2.1 Maria Pyrina submitted her PhD thesis to the University of Hamburg on 27th March 2017(within three years of starting) and successfully defended her PhD on 16th June 2017.
ESR 3.1 Irene Artero Ballesta is aiming to defend her thesis early in 2018 During the 4th year required for a PhD in the Netherlands she is being supported with funding from NIOZ.
ESR 3.2 Ariadna Purroy Albet successfully defended her PhD on March 17th 2017 at the Institute of Oceanography and Fisheries, Split. Subsequent to the end of her contract she has returned to Barcelona, Spain and is currently passing through the administration procedure related to the recognition of her PhD degree in her home country.
ESR 4.2 Liqiang Zhao successfully defended his PhD thesis on March 13, 2017 and received a “summa cum laude” for both the oral part of the thesis and the dissertation. Since the end of his employment through ARAMACC funds, Dr. Zhao has worked as a postdoc at JGU Mainz. In December 2017, he will return to China where he has accepted a permanent Assistant Professorship position at the Institute of Oceanology of the Chinese Academy of Sciences, located in Qingdao. His future research will focus on the ecology and biology of marine bivalves and the implemention of sclerochronological techniques that he acquired and developed at the University of Mainz.
ESR 4.3 Stefania Milano successfully defended her PhD thesis on December 13, 2016 (less than three years after starting, and received a “summa cum laude” for both the oral part of the thesis and the dissertation. Her dissertation thesis was recently awarded a prestigious research prize by the Freunde der Universität Mainz e.V. (http://www.gnk.uni-mainz.de/240.php). Since the end of her ARAMACC contract in March 2017, Dr. Milano has been working as a postdoc with Dr. Gernot Nehrke in the Marine BioGeoscience group at the Alfred Wegener Institute in Bremerhaven on the mineralogical and nanostructural transformation of shell carbonate in relation to thermal diagenesis. Recently, Dr. Milano successfully applied for two year research stipend by the DFG (Deutsche Forschungsgemeinschaft). At the same time, she received an offer by the Max Planck Institute for Evolutionary Anthropology for a six-year postdoctoral fellowship with Prof. Jean-Jacques Hublin, Dr. Klervia Jaouen and Dr. Kate Britton (Department of Human Evolution) which starts in October 2017. The project focuses on stable isotope analyses of Pleistocene shell remains excavated from different paleoanthropological sites in Europe to reconstruct local environmental conditions.
5. Workshop participation and other achievements
ESR 1.1 Fabian Bonitz and ESR 1.2 Tamara Trofimova participated in an ICES working group (WKGIC2) on “Growth-increment chronologies in marine fish: Climate-ecosystem interactions in the North Atlantic”, held in Esporles, Mallorca 18th - 22nd April 2016.
ESR 1.3 Stella Alexandroff spent time at the 14Chrono Centre at the Queen’s University Belfast headed by Prof. Paula Reimer, where she was trained in sample processing and radiocarbon analysis and helped to prepare her own samples for radiocarbon dating.
ESR 1.3 Stella Alexandroff and ESR 1.5 Juan Estrella-Martìnez participated in the summer school “Isotopes in Climate and Earth Systems” on Islay, Scotland, in August 2015 organised by the Bolin Centre/Stockholm University.
Stella Alexandroff was also:
1) a steering committee member of the CNS Women’s Network at the College of Natural Sciences, Bangor University. The women’s network aims to act as a platform for networking opportunities that promote gender equality;
2) PhD course representative at the School of Ocean Sciences, Bangor University, from October 2014 to October 2016;
3) Part of the Athena SWAN self-assessment team of the School of Ocean Sciences, Bangor University. Stella contributed to the school’s application for an Athena Swan Bronze Medal, which is an award given to higher education and research institutions for their efforts to ensure gender equality in employment.
ESR 3.1 Irene Artero Ballesta took part in a number of training events and symposia related to the field of Dynamic Energy Budget modelling:
1) 8-th international tele-course on DEB 2015+ training part in Marseille, France (February 19- March 26 and from April 20 - April 27, 2015.
2) 4th Symposium on DEB theory: Marseille, France (April 28-30, 2015)
3) 5thInternational Symposium on DEB theory (Tromsø) + DEB School, Tromsø : May 21- June 2, 2016
6. Project website
www.aramacc.com
This website is currently maintained by Paul Butler (p.butler@exeter.ac.uk)
The limited coverage (in time and space) of instrumental measurements constrains our understanding of marine change; indeed, the only way in which we can extend the range of real world data is by the use of proxy measurements embedded in natural archives.
The proxy archives contained in marine bivalve shells are one powerful way in which we can do this. These archives are unique in that they are periodically (usually annually) resolved, replicable, and specific to the marine realm. Their study has given rise to a new scientific field (molluscan sclerochronology) and the development and consolidation of this field has been the aim of the multi-partner Marie Curie ITN reported here (ARAMACC: “Annually Resolved Archives of Marine Climate Change”).
In summary, twelve fellows (ten ESRs and two ERs) based at eight partners worked on eleven distinct subprojects. In the spirit of ITNs, the fellows were provided with a diverse training programme that addressed all aspects of the field of sclerochronology. The ARAMACC fellows were recruited from a range of countries (China, Germany(3), Greece, Italy, Russia, Spain(2), Sweden, UK, USA), and the gender split was 8 female to 4 male.
All ten ESRs completed their three-year contracts and successfully completed their research programmes. Five of them also completed their PhDs before the end of their contracts or shortly afterwards, while the other five are in the process of writing up. Four of the ESRs have either started or been offered postdoc positions. Seventeen peer reviewed articles have been published or accepted and a further nine have been submitted.
All the generic and specialist training was delivered as described in the original proposal, including two research cruises that also provided training in carrying out science at sea. With just two exceptions there was 100% attendance by all Fellows at the training events. The training events were fully open and thirteen spaces at the various training events were taken by participants from outside ARAMACC.
Among the major science achievements were: (i) the development of new proxies for ambient temperatures based on shell crystal fabrics; (ii) new and detailed findings on the incorporation of trace elements into the shell; (iii) detailed work on valve gape and feeding activity by clams; (iv) the resolution of an outstanding species identification issue for the Adriatic Sea; and (v) significant development of the potential of the bivalve proxies for model data assimilation. In all, six new absolutely-dated multicentennial or multidecadal chronologies, anchored to the present day, were developed for the Faroe Islands (east and west), Viking Bank and Fladen Ground in the northern North Sea, the isolated Scottish Hebridean island of St Kilda, and the Bay of Brest in France. In addition, two floating chronologies for a period approximately 3,500 yrs BP were developed for St Kilda and verified by radiocarbon dating.
Dedicated ARAMACC sessions, convened by the ARAMACC fellows, took place at European Geophysical Union (EGU) conferences in 2015 and 2017. These attracted around 30 abstracts, most from people outside the ARAMACC consortium, and filled one (in 2015) and two (in 2017) oral sessions respectively, with the 2017 sessions being particularly well attended, and including some prominent palaeoclimate scientists. ARAMACC was also well represented at the Arctic Frontiers (AF) conference in Tromsø in January 2017, with the final ARAMACC training event being integrated into the AF Young Scientists Forum.
ARAMACC was strongly represented at several other major international conferences, and, in particular, ARAMACC participants made a very strong contribution to the 4th International Sclerochronology Conference, held in Portland, Maine, USA in June 2016. This contribution was likely decisive to the success of the conference, and perhaps even to the short-term cohesion of the whole field of sclerochronology.
2. Project context and objectives
The context of ARAMACC is the ability to use environmental proxies in the shells of marine bivalve molluscs as monitors of past marine conditions. These shells contain periodic (usually annual) banding, which enables each part of the shell to be precisely and accurately dated. In addition, some species are very long-lived and grow synchronously within populations, so that dead shell material can be dated (“crossdating”) by comparing their banding patterns with similar patterns in live-collected shells. Essentially, these bivalves function as a marine equivalent of the terrestrial tree-ring archive, providing proxy measurements of environmental variables at annual and subannual resolutions. The ability to crossdate banding patterns enables the creation of chronologies from multiple shells (so that proxy measurements can be replicated), and these chronologies can extend back in time for centuries or even millennia before the onset of the industrial age. By analogy with the equivalent scientific field in tree-ring research (“dendrochronology”) this new field is known as “sclerochronology”
Before the development of the ARAMACC proposal, the field had advanced incrementall, through a few individual projects. These indicated the potential of molluscan sclerochronology, but inevitably none of them was able by itself to address the full range of associated disciplines.
For any environmental proxy to be effective, it is necessary to understand the mechanisms linking the ambient environment to one or more proxy measurements. These mechanisms may be physical, chemical or biological, and they include the biological drivers of shell growth, the chemical and kinetic processes that drive isotopic fractionation and the uptake of trace elements in the shell carbonate, and the processes that determine variation in the crystal structure.
It is also necessary to identify and develop applications of the proxy; these include the development of long term proxy-based baseline measurements (ie environmental reconstructions) for use in the commercial and regulatory sectors, and the use of the proxy data for model verification and data assimilation.
Broadly, the ARAMACC objectives were split into science (work packages 1-4) and training (work packages 5-6) WPs.
ARAMACC science
The objectives of ARAMACC science were to address (1) the construction of a network of shell-based chronologies for the climatically important NE Atlantic region; (2) the use of data from these and other existing chronologies for multicentennial model comparisons and to constrain model predictions on decadal timescales; (3) the ecological and biological drivers of calcification rate and increment formation; (4) the development of novel proxies using the geochemistry and crystal structure of the shell material; (5) the use of sclerochronological techniques to produce baseline environmental data for the commercial and regulatory sectors and the promotion of these techniques to the appropriate organisations; and (6) to establish a public data bank of all sclerochronological data (with metadata) from the North Atlantic realm. These objectives are described in more detail below:
(1) The construction of a network of shell-based chronologies for the climatically important NE Atlantic region (WP1).
The initial objectives were:
(a) to build a network of shell-based chronologies (ie proxy archives) for the NE Atlantic region along a transect along the axis of the North Atlantic Current, the main goal being to reconstruct the hydrographic variability of the meridional overturning circulation in the North Atlantic during the Holocene, in particular over the past 1000 years, and to assess the role of the oceanic system in key climate transitions;
(b) where curated shell material was not already available, to collect new material during shell collection campaigns at sea;
(c) once the chronologies were built, to sample the dated material for targeted geochemical (stable isotope and trace element) analyses in order to reconstruct (a) annual to decadal variability through key climate transitions and (b) seasonal variability during distinct climatic states;
(d) to deliver the proxy data to external users in the climate modelling community for incorporation into numerical models of the climate system.
(2) The use of data from these and other existing marine chronologies for multicentennial model comparisons and to constrain model predictions on decadal timescales (WP2).
The initial objectives were:
(a) to develop the use of shell-based proxy records as a tool for model analysis of the amplitude and structure of decadal and multidecadal climate variability in the North Atlantic region;
(b) to constrain the characteristics of model simulated variability, so that the model processes that drive similarities or discrepancies with the real-world data can be identified, thus enabling more realistic model analyses of ocean-atmosphere coupling on these time scales;
(c) To analyze the successful simulations in more detail with the aim of identifying predictors at decadal timescales that can be verified in the proxy records and, in a more limited time frame, in recent instrumental measurements.
(3) The ecological and biological drivers of calcification rate and increment formation (WP3).
The initial objectives were to identify ecological, biological and behavioural drivers that:
(a) precipitate the annual cessation of growth and the formation of the growth check;
(b) affect the seasonal variation in calcification rate;
(c) control longevity;
(d) generate variability in individual responses to the common environmental signal.
These drivers and responses were to be investigated for multiple species using known techniques, including shell marking, gape monitoring and within-increment geochemical analysis.
(4) The development of novel proxies using the geochemistry and crystal structure of the shell material (WP4 part 1).
The initial objectives were:
(a) using controlled growth experiments, to analyze in what proportion, relative to ambient water (and the extrapallial fluids if possible), trace elements are incorporated in shells of cultured and naturally occurring bivalves from different settings;
(b) to develop a model of crystal fabric structures based on the observed patterns and develop an image processing tool for the automated mapping and quantification of crystal fabrics.
(5) The use of sclerochronological techniques to produce baseline environmental data for the commercial and regulatory sectors and the promotion of these techniques to the appropriate organisations (WP4 part 2).
The initial objectives were:
(a) to develop the use of sclerochronological techniques as a monitoring tool of use to the commercial and regulatory sectors;
(b) to use the temporal extent of the chronologies to produce long term baseline data for use in the commercial and regulatory sectors;
(c) to interface between the commercial and academic sectors to maximize the potential commercial exploitation of long-lived bivalves in environmental monitoring by identifying new sampling strategies, identifying new species for sclerochronological analysis and identifying opportunities to apply crossdating and geochemical techniques in existing and ongoing environmental contracts;
(d) in collaboration with the commercial and regulatory sectors, to initiate the development of protocols for the routine incorporation of shell series into environmental monitoring and the exploitation of commercial sampling for climate change applications.
(6) The establishment of a public data bank of all sclerochronological data (with metadata) from the North Atlantic realm (WPs 1, 3, 4).
The primary objective was to ensure that all data produced during ARAMACC was appropriately warehoused.
ARAMACC training
The overall objective of ARAMACC training was to develop a cadre of highly-trained scientists with a range of overlapping and cross-disciplinary skills who are fully committed to the use of high-resolution shell-based archives to increase scientific understanding of the part played by the oceans in the Earth’s complex climate system. With this background, they will be able to apply their skills to the study of past and future climate change and to the goal of ensuring that the use of the shelf seas for infrastructure projects is genuinely sustainable and fully informed. In the process, the competitiveness of European climate science and the commercial value of sclerochronological techniques will be enhanced, together with the geographical mobility and cross-disciplinary range of individual researchers. ARAMACC training had two main complementary objectives, described in detail below:
(1) To provide training in generic and transferable skills (WP5).
The objective of WP5 was to provide a full programme of generic and transferable skills training was provided, specifically including:
(a) research management;
(b) scientific writing and publication;
(c) attracting funding;
(d) entrepreneurship and commercial exploitation;
(e) career development;
(f) dissemination, communication and public outreach
(2) To provide training in scientific skills specific to the field of sclerochronology (WP6).
The objective of WP6 was to provide a full programme of scientific skills specific to the field of sclerochronology, including:
(a) techniques for research at sea;
(b) chronology construction using growth increments in shells;
(c) geochemical techniques in sclerochronology;
(d) ecology of long-lived bivalves;
(e) sclerochronology and numerical modelling ;
3. Main science & training results
ARAMACC Science (work packages 1-4)
ARAMACC science consisted of ten subprojects carried out by ESRs and one project carried out by an ER, divided into four work packages (WPs) and based at eight beneficiaries
WP 1 - The construction of a network of shell-based chronologies for the climatically important NE Atlantic region
WP 1 consisted of five projects, each led by one ESR, and was based at three beneficiaries:
ESR 1.1 Fabian Bonitz, based at UniRes Bergen.
ESR 1.2 Tamara Trofimova, based at UniRes Bergen.
ESR 1.3 Stella Alexandroff, based at SOS Bangor.
ESR 1.4 Amy Featherstone, based at UBO Plouzané.
ESR 1.5 Juan Estrella-Martínez, based at SOS Bangor.
ESR 1.1 Fabian Bonitz: “Variability of Atlantic inflow using sclerochronology (1): Faroe inflow branch” (beneficiary UniRes Bergen)
The aim of this project was the investigation of natural climate variability in the northern North Atlantic over the past few hundred years using natural archives in the shells of Arctica islandica from the Faroes Shelf. Shells were collected during a cruise of the Norwegian research vessel G.O.Sars during November 8th-17th 2014. Annual banding in the shells was used to build a statistically robust multi-centennial master chronology covering the time period AD 1642-2013. The shell growth index of this chronology was found to be strongly positively correlated with phytoplankton dynamics from the Faroese region, so that higher (lower) phytoplankton concentrations are associated with wider (narrower) growth increments. This relationship can be observed on both inter-annual and multi-decadal timescales, allowing the shell growth index to be used as a tool to identify periods/years with increased or decreased phytoplankton concentrations. In the Faroese region, where phytoplankton dynamics are strongly connected to higher trophic levels (e.g. fish stocks), such information for periods before the availability of instrumental observations can be used to estimate historical changes in stocks of commercially important marine resources, such as cod and herring.
Geochemical analysis of the 13C composition of the shell carbonate through time revealed that evidence of the oceanic Suess effect (ie the increase in the ratio of 12C to 13C in the environment that results from anthropogenic emissions of carbon derived from fossil fuels) is preserved in the shell carbonate. In this region, the onset of the oceanic Suess effect seems to occur in the latter half of the 19th century. This is an important finding, since the regional partitioning of the uptake of anthropogenic CO2 by the oceans, and its history, are key factors in the study of the mechanisms by which the global ocean acts as a sink for excess atmospheric CO2. This knowledge will in turn help researchers and climate modellers to assess future changes in the ability of the oceans to act as a buffer for CO2 emissions. The results from this geochemical analysis therefore constitute an incremental step towards this crucial goal.
Geochemical analysis of the 18O composition of the shell carbonate was used to obtain a water temperature record with annual and subannual resolution. The extension of this record to periods before the start of instrumental observations and before the period of major human impacts will help to provide a baseline for the objective evaluation of the impacts of anthropogenic climate change in the Faroese region.
ESR 1.2 Tamara Trofimova: “Variability of Atlantic inflow using sclerochronology (2): northern Norway” (beneficiary UniRes Bergen).
The original aim of this project was the investigation of natural climate variability in the far northern North Atlantic over the past few hundred years using natural archives in the shells of Arctica islandica from the northwest and northern coasts of Norway. Initial campaigns indicated that it would be difficult to obtain sufficient amounts of shell material from these sites, so the focus of the project was shifted further south to a site on the Viking Bank in the northern part of the North Sea. Shells were collected from a depth of about 100 metres during the same G.O.Sars cruise that provided material for ESR1.1. Annual banding in the shells was used to build a statistically robust 265-year long master chronology.
Seasonally and annually resolved geochemical samples (stable oxygen and carbon isotope measurements) were obtained from shells that had been included the same master chronology. These records together provide new insights into the hydrographical variability of the North Atlantic current, in particular into temperature variability and the marine 13C Suess effect.
Shells that had been radiometrically dated to 9600-9335 cal. yr BP were used to build a 240- year long record of shell growth from the early Holocene, providing new data on the decadal scale variability of shell growth at this time. Geochemical analysis of this material has been used to build a 22-year seasonally-resolved oxygen isotope record, providing an indication of the seasonal variability of bottom water temperature on the Viking Bank during the early Holocene. This research has also contributed new independent data related to sea-level changes on the Viking Bank.
A proxy improvement study was carried out in collaboration with ARAMACC beneficiary JGU Mainz to assess the possible influence of crystal habits on the stable isotopic composition of shells and hence their potential effect on paleoclimate reconstructions. This part of the research is important for the interpretation of oxygen isotope paleothermometry.
ESR 1.3 Stella Alexandroff: “Variability of Atlantic inflow using sclerochronology (3): Scotland-Norway branch of the North Atlantic Current” (beneficiary SOS Bangor).
The aim of this project was the investigation of natural climate variability in the Scotland-Norway branch of the North Atlantic Current over the past few hundred years using natural archives in the shells of Arctica islandica from waters off the west coast of Scotland. Shells were collected during a cruise of the SOS Bangor research vessel Prince Madog during May 27th – June 3rd 2014. The cruise was planned and co-organized by the ESR.
Two floating chronologies and one modern chronology have been constructed using shells from St Kilda, an island group situated on the western Scottish shelf about 70km off the Outer Hebrides and strongly influenced by oceanic conditions. Both floating chronologies were constructed using shells from Glycymeris glycymeris that lived approximately 3500 years ago (determined by radiocarbon dating). Each chronology (consisting of seven and two shells respectively) spans approx. 200 years. The modern chronology, spanning 131 years (AD 1885-2015), was built using Arctica islandica shells recovered by divers from the same location. Shells from live collected specimens of G. glycymeris were also used for geochemical analysis, but these shells were not positioned in a chronology as they were very short-lived (with lifetimes of the order of 12-20 years)
Average growth in the modern chronology shows significant correlations with North Atlantic sea surface temperatures (SSTs) since 1981 and with North Atlantic sea surface salinity since 1900.
Radiocarbon dating of the shells in the floating chronologies was consistent with the relative dating indicated by crossmatching, thus confirming the reliability of both techniques.
Sub-annually resolved oxygen isotope samples were taken from: (1) shells from one of the floating G. glycymeris chronologies, (2) shells from the modern A. islandica chronology and (3) live collected G.glycymeris. The stable oxygen isotope ratios (δ18O) in the modern shells (both species) converted to regional instrumental sea surface temperatures (SSTs) using standard palaeotemperature equations without any need for correction. This finding confirms that shell δ18O is a reliable proxy for SST in both species at this location and that it can be used for reconstructions of SST. Comparison of δ18O in the fossil G. glycymeris with that in the modern G. glycymeris demonstrates that (1) the seasonal range of SST was considerably higher in the 4th millennium BP, and (2) the annual mean SSTs were cooler than they are today.
ESR 1.4 Amy Featherstone: “Construction of long annually-resolved shell-based chronologies using Glycymeris glycymeris from the Bay of Brest, France” (beneficiary UBO Plouzané)
The main objective of this project was the construction of long annually-resolved chronologies using annual growth increments in the shells of the dog cockle, Glycymeris glycymeris.
The initial goal was to work with specimens collected in NW France, Croatia and Iberia. However, because of the lack of availability of sufficient material in some areas, the geographical extent of the project was eventually restricted to the Bay of Brest, France.
The main research goals of the project did not change, being (i) to build a long annually resolved shell-based growth chronology and relate changes in shell growth over time to environmental variables and climate forcings; (ii) to use stable oxygen isotope geochemistry to reconstruct temperature variations in the Bay of Brest over the past few decades; and (iii) to investigate the potential of trace element concentrations in the shells as proxies for seawater temperature, salinity, phytoplankton dynamics and possibly pollution.
Sampling took place every month at a site close to the outlet of the Bay of Brest, at an average depth of 20 m, between September 2014 and November 2015. In all, several hundred live clams and dead shells were collected by dredging. Soft tissues were removed and kept frozen for subsequent biological analyses. Some tissues were stored in ethanol for genetic analyses (this being a collaboration with IOF Split). The shells were carefully labelled and stored in the lab and made available on request to other partners in the ARAMACC project.
A sub-sample of thirty-eight specimens (twenty live-collected and eighteen dead-collected shells) was selected based on morphometric measurements (on the assumption that the largest and heaviest and longest specimens would also be the longest lived). The shells were processed using standard sclerochronological techniques (embedding in resin, cross-sectioning, polishing and production of acetate peel replicas of the banding in the hinge area). The longest-lived specimen was found to be 70 years old. A shell master chronology spanning 1891 to 2014 was built using standard tools derived from dendrochronology. This chronology is statistically robust (Expressed Population Signal, EPS > 0.85) for the last 40 years, but sample depth is very low before 1975. The position of four of the shells in the chronology was verified by radiocarbon dating. Correlation of the annual growth indices with local environmental factors indicated that the predominant drivers of shell growth were river inflow, salinity and suspended particulate matter.
Geochemical analysis was carried out on a sub-sample of the shells that had been used for chronology building. A total of 24 specimens of different ages were analysed for the stable oxygen isotope ratios (δ18O) in their shell, with sampling restricted to the ontogenetically youngest portions of these specimens so that the seasonal cycle could be observed. The samples were run by the ESR during a secondment at JGU Mainz. The main results show that variations in shell δ18O accurately record local sea surface temperatures, allowing the creation of a 45-year SST reconstruction for the Bay of Brest (1966-2010). Correlations between this and climate forcings indicate that SST variations in this area may be partly controlled by the strength of the subpolar gyre and the East Atlantic Pattern.
In addition, five shells (three under the age of 10 and two aged 45) were analysed using an LA-ICP-MS system to determine the elemental composition of the shell aragonite (magnesium, strontium, barium, manganese, boron, lead, uranium, and calcium). These results were obtained quite late during the PhD project and further analysis will be required before they can be interpreted as proxies for environmental variables.
Overall, this study confirms the potential of G. glycymeris as an archive of climatic and environmental variability in the Bay of Brest. As there are a large number of sub-fossil specimens in the area, there is good potential to extend the chronology further back in time.
ESR 1.5 Juan Estrella-Martínez: “Holocene climate variability in UK waters based on Arctica islandica sclerochronology” (beneficiary SOS Bangor)
The initial aim of this project was the investigation of natural climate variability in UK waters (specifically the Irish Sea and North Sea) during the Holocene using natural archives in the shells of Arctica islandica. As all the required shells were already in curated collections held at SOS Bangor and NIOZ Texel, no shell collection campaign was required. Time constraints resulted in the Irish Sea shells being removed from the remit of the project, which has concentrated on material from the Fladen Ground, northern North Sea held in the collection at SOS Bangor.
This project consisted of two major subprojects: (1) The extension of the Fladen Ground A. islandica chronology to AD 1551; (2) an early Holocene floating chronology that is thought to cover the 8.2Ka cold event.
1. The extension of the Fladen Ground A. islandica chronology to AD 1551.
An existing published chronology for the Fladen Ground, northern North Sea (Butler et al., 2009) extends back to AD 1870. In this subproject, the chronology was extended back to AD 1551 with the addition of more shells from the SOS Bangor collection. A temperature equation for shell 18O was developed by calibrating subannual samples to measured bottom water temperatures (BWT) from the same geographical area. The calibration indicated that the growing season for A. islandica in the Fladen Ground is March-August. The temperature equation was used to reconstruct mean March-August BWTs for the 454 years AD 1551-2004. While more analysis of this time series is required (and is currently underway), there are indications of a dynamical link between the reconstructed BWTs and the Scandinavian Pattern that is most evident following large tropical volcanic eruptions. Spatial correlations between the reconstructed BWTs and measured sea surface temperatures show a clear stratification signal, with the timing of stratification appearing to be linked to the strength and sign of the spring summer NAO index.
2. An early Holocene floating chronology that is thought to cover the 8.2Ka cold event
A 200-year floating chronology, containing three fossil shells from the Fladen Ground, was constructed. Radiometric dating of the three shells (incorporating the global modelled marine reservoir correction) indicated a date in the early Holocene around 8,300 years BP (where present = AD 1950). Stable oxygen isotope measurements showed a marked increase in the 18O ratio (corresponding to colder bottom water temperatures if the 18O of the seawater is assumed constant) during a 55-year period in the middle of the chronology. On the basis of the radiometric dating, this 55-year period is offset from the 50-year cold period that marks the so-called “8.2Ka cold event” in the Greenland ice cores by about 141 years. If the two isotope excursions are in fact contemporaneous, this would indicate a local reservoir correction (R) of -141 years suggesting greater ventilation of North Sea waters during the early Holocene, consistent with shallower waters at the time.
WP 2 – Integration of sclerochronological data from multiple sites into numerical models
WP2 constituted the climate modelling part of the ARAMACC project. The goal of this part of the project was to develop optimum methods to integrate the network of shell-based chronologies developed in WP1 with the current generation of climate models. WP2 consisted of a single subproject.
ESR 2.1 Maria Pyrina: “The use of proxy data from molluscan sclerochronology for model comparison and decadal prediction“ (beneficiary HZG Geesthacht)
The technical aim was to analyze the amplitude and spatial structure of decadal and multi-decadal climate variability in the North Atlantic region by combining the output of climate model simulations with proxy-based reconstructions of past climate. While proxy data from single Arctica islandica populations has previously been used to reconstruct local climate, no bivalve proxy has so far been used for the reconstruction of large scale climate patterns in the North Atlantic basin. The project was developed around five principle research questions:
1. Does A. islandica have the potential to be used in climate field reconstructions (CFRs) of North Atlantic SSTs?
2. If there is a North Atlantic basin signal registered at sites occupied by A. islandica populations, which CMIP5 models best reproduce that signal?
3. Which climate reconstruction techniques are best suited for the reconstruction of SSTs based on records from A. islandica?
4. Is the climate model method or the statistical reconstruction method more important for the evaluation of the skill of the reconstruction?
5. Do changes in solar forcing affect summer upper ocean circulation?
In order to use proxy records from A. islandica in CFRs of the North Atlantic climate, it was first necessary to investigate the co-variability of these records in the North Atlantic. In a second step, aiming to combine the local information provided by A. islandica into the broader context of large scale climate patterns, different statistical methods were assessed using controlled pseudoproxy experiments (PPEs). As it is a prerequisite for the construction of a meaningful PPE that the climate model is able to represent realistic spatiotemporal characteristics of the observed climate, the climate models used as the basis of the PPEs were evaluated for their ability to simulate North Atlantic spatiotemporal climate variability.
A very significant outcome of WP2 was the finding that the sites occupied by A. islandica populations in the northeast Atlantic constitute an effective network for the reconstruction of large scale climate in the northeast Atlantic basin. In addition, the assessment of various statistical methods that can be applied to climate field reconstructions based on the A. islandica network found that both Principal Component Regression and Canonical Correlation Analysis can be used for the reconstruction of large scale climate based on the comparatively sparse A. islandica network (the assessment of statistical methods is an important methodological step, as the quality of past climate reconstructions largely depends on the statistical method applied.) In addition, it was found that only a subset of current state-of-the-art models are appropriate as realistic test beds, and that the model used affects the skill of the climate field reconstruction more than the statistical method applied.
In addition to these assessments of climate reconstructions for the North Atlantic basin, and in order to obtain a better understanding of the impact of changes in external forcings, the drivers of North Atlantic sea surface temperature variability during the preindustrial era of last millennium were investigated. The results of this test indicated that phases with lower solar activity might be linked to blocking-like atmospheric circulation in the North Atlantic basin.
WP 3 – Ecological and biological drivers of calcification rate and increment formation
The fundamental scientific aim of WP 3 was to better understand the environmental factors that control increment variability in long-lived marine bivalve molluscs and consequently to develop tools to improve the interpretation of palaeo-environmental reconstructions based on growth increment series derived from these species.
WP 3 consisted of two projects, each led by one ESR, and based at two beneficiaries:
ESR 3.1 Irene Ballesta Artero, based at NIOZ Texel.
ESR 3.2 Ariadna Purrot Albet, based at IOF Split.
ESR 3.1 Irene Ballesta Artero : “Ecological and biological drivers of calcification rate and increment formation” (beneficiary NIOZ Texel)
This work can be subdivided into three subprojects:
1. The in situ study of animal behaviour in relation to seasonal and environmental variability. This is being addressed during experimental work in northern Norway where in situ monitoring of the valve gape behaviour of Arctica islandica has been ongoing since the start of the project. The results to date show that in a natural setting the presence of food is the most important driver of gaping activity. As a result of this work, the ESR has collaborated with a research group working on similar topics at the Institute of Environment and Marine Science Research (IMEDMAR) in Spain.
2. The laboratory-based study of the interacting influences of temperature and food availability on shell growth. This was addressed during an extensive laboratory-based growth experiment over a three-month period during which the interacting influences of temperature and food supply on behaviour and growth were studied. The data have been analyzed and the resulting manuscript (“Interactive effects of temperature and feeding conditions on the growth of Arctica islandica juveniles”) will be submitted shortly. The geochemistry of these experimentally grown shells are being used for chemical analyses of the carbonate composition in cooperation with the ARAMACC partner at JGU Mainz.
3. The analysis of energy budgets devoted to reproduction and growth increment formation, and the construction of a dynamic energy budget model from which growth, food or temperature conditions can potentially be derived. This subproject has been addressed through the organization (by the ESR in collaboration with a local fisherman in Norway) of the collection of monthly shell samples for the analysis of reproductive state and condition. These samples form the basic data for the development of a DEB (Dynamic Energy Budget) model for A. islandica. To obtain the skills required for the construction of a DEB model, the ESR joined a two-week symposium which included skills exchange with all the major experts in this field.
Both experimental and in situ experiments have shown that food supply is a major driver of A. islandica shell growth in Arctic conditions. These experimental results can be used to refine and improve the use of A. islandica as an archive for palaeoceanographic reconstruction, and further enhancement, including model integration, will be made possible with the development of a DEB model for A. islandica.
ESR 3.2 Ariadna Purroy Albet: “The ecological and biological drivers of calcification rate and increment formation in Glycymeris spp.” (beneficiary IOF Split).
All the practical experiments in this project were undertaken in situ, beginning in May 2014 and continuing until October 2015. The ESR conducted monthly field sampling at three locations in the eastern Adriatic Sea (Pag Bay, Cetina river estuary and Pašman channel). The target species were Glycymeris bimaculata, Glycymeris pilosa (initially thought to be Glycymeris glycymeris) and Callista chione. In addition to the bivalve samples, samples from the water column and sediment were also collected. Laboratory analysis started in parallel with the field sample collection and included measurement of the gonadosomatic index, histological analysis of the gonads, and analysis of stable isotopes and fatty acids in bivalve digestive gland and potential food sources. Geochemical analysis of soft tissue (stable isotopes of nitrogen and carbon) and shell material (stable isotopes of oxygen and carbon) was carried out at the ARAMACC partner at JGU Mainz. The analysis of the shell material was undertaken by the ESR on secondment at JGU Mainz.
The results of this work clearly indicate spatial and temporal variations in environmental characteristics and trophic ecology of the target species. The best food quality in the particulate matter was observed during spring and summer and food resource partitioning was observed between C. chione and G. bimaculata. Inter-site variations in the spawning timing and duration of C. chione were likely associated with temperature whereas in Glycymeris spp. spawning did not seem to be not directly connected to temperature. Shell growth in Glycymeris spp. took place between May and December indicating that temperature is an important determinant of shell growth. The results indicate that the growth season is limited by food availability.
This work has significantly contributed to the development of bivalve sclerochronology research in the Adriatic and Mediterranean Seas by developing a detailed characterization of the target species in relation to their environment. It indicates the value of coupling sclerochronology to ecological studies for a better understanding of species life-history traits. Important results were obtained relating to the ecology of the long lived bivalves G. bimaculata and G. pilosa, and to the ecology of the commercially important species C. chione. These results have potential for application in management and protection of natural populations of C. chione and provide a better understanding of the trophic ecology and reproductive processes of the studied species.
Ariadna Purroy collaborated with other ARAMACC ESRs including Liqiang Zao and Stefania Milano (ESR4.2 and ESR 4.3 based at JGU Mainz) and Amy Featherstone (ESR1.4 based at UBO Plouzané). These collaborations resulted in joint manuscripts which have been published, are under review or in preparation.
WP 4 (part 1) – Novel applications and proxy development
WP 4 part 1 focused on the formation mechanisms and interpretation of geochemical and crystallographic proxy data fund in the shell material. The fundamental science aim was to generate novel proxies for the reconstruction of key environmental variables.
WP 4 part 1 consisted of two projects led by two ESRs and based at a single beneficiary:
ESR 4.2 Liqiang Zhao, based at JGU Mainz.
ESR 4.3 Stefania Milano, based at JGU Mainz.
ESR 4.2 Liqiang Zhao: “Trace element incorporation into shells” (beneficiary JGU Mainz)
The primary goal of this project was to evaluate the extent to which the trace and minor element chemistry of bivalve shells can be employed as a tool for the reconstruction of environmental variables. Bivalves closely control the amount and type of trace and minor elements that are incorporated into the shells, although this can result in the modification of their microstructure and consequently negatively affect the mechanical properties of the shells. As a result, the element levels in the shells typically remain far below those in the ambient environment and far below those of synthetic precipitates of CaCO3.
To address these issues, the ESR conducted a series of controlled tank experiments with living bivalves during which selected environmental parameters were modified. After the end of each experiment, the chemistry of the shell portion that formed during the experimental phase was investigated and compared to the respective growth conditions. To identify the mechanisms by which the different ions are transported from the water to the site of shell formation, the ESR also added substances to the tank water that blocked the activity of certain enzymes and ion channels of the mantle epithelium, i.e. active and passive transport mechanisms.
These studies clearly demonstrate that the trace and minor elements of the studied bivalve shells recorded environmental conditions. Findings have been presented at various international conferences and reported in five papers that were published in international peer-reviewed scientific journals. The main outcomes are briefly reported below.
Because the incorporation of elements into minerals is in part driven by thermodynamic fractionation effects, the trace and minor element content of a mineral can potentially reflect environmental conditions during mineral formation. In living organisms, the elements in the water must pass through semipermeable membranes (in bivalves: the mantle epithelia) to reach the site of hard part formation. In bivalves, this is accomplished by enzyme-mediated carriers such as Ca2+-ATPase, through Ca2+ channels, and by passive diffusion through ion channels. Elements that can freely (passively) move across semipermeable membranes are considered more suitable for environmental reconstructions, because their concentration in the extrapallial space reflects that of the ambient water. The other two mechanisms require energy and are thus biologically controlled.
To identify the mechanisms by which selected elements are transported across epithelial membranes, the ESR used Corbicula fluminea as a model organism. This bivalve tolerates a wide range of temperature (0-43°C) and salinity regimes (up to 24 PSU). Results may thus be applicable to both freshwater and marine ecosystems. The ESR first deactivated the Ca2+-ATPase enzyme with Ruthenium Red and then blocked Ca2+ ion channels with lanthanum and Verapamil. As a result, the concentrations of manganese, copper and lead in the shells of this species decreased, but magnesium, strontium and barium levels remained unchanged. These findings suggest that Sr, Mg and Ba of shells of the studied species can potentially serve as proxies of environmental conditions (Zhao et al. 2017a).
A subsequent experiment (Zhao et al. 2017b) investigated an aspect of bivalve sclerochronology that has been controversially debated for a long time, i.e. whether strontium and barium can be used as proxies of water temperature and primary productivity respectively. The results indicate that, while C. fluminea closely tracks changes of the Sr and Ba content of the ambient water, the distribution coefficients of both elements were lower than expected for equilibrium precipitation. For example, the concentration of Sr in the shells is four times lower than it is in the ambient water and the extrapallial fluid, suggesting that another biological mechanism controls the transport of ions into the shells; this might be a macromolecular ion selection at the calcifying front. In spite of that complication, increasing ambient water temperatures were faithfully recorded as decreasing Sr/Ca ratios in the shells. In conclusion, as long as Sr levels in the water remain constant, the Sr/Ca ratio of the shells provides a reliable tool for reconstruction of past water temperature.
Interpreting the Ba/Ca ratios in the shells is less straightforward because they are affected by a combination of phytoplankton abundance, growth rate and temperature. To reconstruct primary productivity changes from Ba/Ca values, ambient temperature and shell growth rate must be known.
The third study (Zhao et al. 2017c) investigated how two selected bivalve species (Mytilus edulis and Patinopecten yessoensis) are affected by ocean acidification and temperature rise (these being two major consequences of present day global change). This study also investigated the possibility of using shell Na/Ca as a proxy for pH. Ocean acidification increases the number of protons in the water and, consequently, in the extrapallial fluids. Some species such as Mytilus edulis are capable of actively removing excess protons from body fluids using Na+/H+ pumps. Since this enzyme exchanges one proton for one sodium ion, sodium levels in body fluids will increase and, potentially, so will those in the shell. Since this active proton removal requires energy, one would expect slower growth rates. This was indeed the case: mytilid specimens exposed to low pH showed higher Na/Ca ratios in the shell and grew more slowly, showing that shell Na/Ca can serve as a proxy for ocean acidification. Patinopecten yessoensis, on the other hand, does not possess a Na+/H+ pump, so that shell Na/Ca ratios and shell growth rate remained unchanged when pH decreased. Temperature rise also had opposite effects on the shells: the mytilid grew faster, the pectinid slower. Anthropogenic climate change thus affects both species, but in different ways, so that P. yessoensis is more resilient to ocean acidification, while M. edulis can better cope with ocean warming.
A subsequent study (Zhao et al. 2017d), investigated epigenetic effects on the tolerance of Ruditapes philippinarum to ocean acidification. Offspring of parents that were already exposed to lower pH could cope better with acidified conditions and grew faster than offspring of parents that lived in neutral seawater. Irrespective of pH levels which the parents experienced, the sodium levels in the shells of the offspring were increased implying active removal of excessive protons through the Na+/H+ exchanger. Furthermore, the offspring of parents that lived in acidified water showed lower shell sodium levels than those of the parents from neutral seawater. These results demonstrated that some species have a capacity to acclimate or adapt to ocean acidification.
The final study (Zhao et al. 2017e) evaluated the use of manganese in shells of Hyriopsis cumingii as an indicator of eutrophication. Results confirmed the hypothesis. Under reducing conditions, Mn is biologically available for the bivalves and can be incorporated into the shells. After phytoplankton blooms, the amount of organic detritus at the seafloor increases and oxygen levels decrease. In turn, this increases the solubility of Mn in the water which is inhaled by the bivalves, resulting in higher Mn levels in the shells. Manganese could be used in future studies aiming to reconstruct pollution histories.
ESR 4.3 Stefania Milano: “Exploring the potential of shell crystal fabrics as novel environmental proxies” (beneficiary JGU Mainz)
The aim of this project was to develop and calibrate new microstructure-based environmental proxies, adding a quantitative element to previous work on the relationship between shell microstructure and temperature, which had been purely descriptive.
For her first study (Milano et al. 2017a), Stefania Milan, selected the short-lived (ca. 6 year-old) common cockle, Cerastoderma edule as target species. For calibration purposes, CTD loggers were deployed in the intertidal zone of the southern North Sea recording temperature and salinity over more than one year on an hourly basis. During the same time interval, water samples were collected nearly every week to determine δ18Owater, element concentration and salinity (to verify CTD data). Chlorophyll a concentrations and turbidity data were obtained from satellite records (MODIS). From the locality where the logger was deployed and water samples were taken, living specimens of C. edule (different age classes) were collected during and at the end of the monitoring phase. In arbitrarily selected specimens, the (crossed-lamellar) microstructure of the outer shell layer between annual growth lines was studied in radial cross-sections, and morphological characteristics, here size and elongation (= dimensionless shape descriptor, ratio between the major and the minor axes) of individual biomineral units were quantified by means of image processing techniques (= semiautomatic particle recognition and measurement). For comparison with the lowest resolved environmental data, measurements were completed in shell portions resembling ca. one week of growth. Within each of these sample regions, the average size and elongation of hundreds of biomineral units was computed and then compared to instrumental data. The studied shell portions were temporally aligned using daily growth patterns. The results showed that the average size (R = 0.80; R2 = 0.64; p < 0.0001) and elongation (R = 0.52; R2 = 0.27; p < 0.0001) of biomineral units of the studied species were significantly positively correlated to ambient water temperature during the growing season, but not to any other measured environmental variable (ie salinity, chlorophyll a level, turbidity or shell growth rate (daily increment width)) (Milano et al. 2017a).
Throughout the lifetime of this fast-growing species, the observed relationship did not change, i.e. the dimensions of the biomineral units were not affected by ontogenetic age-related trends, but were exclusively correlated to water temperature. Based on these data, a transfer function was computed that can be used to reconstruct temperatures from the dimensions of the biomineral units of C. edule with a 1σ precision error of ±1.5°C. The functioning of the new proxy has been successfully tested on specimens from another locality (Milano et al. 2017a). Our findings were recently corroborated by Gilbert et al. (2017 EPSL 460, 281-292) for different species of Atrina and Pinna. Their results demonstrated that the nacre tablet thickness in these (likewise fast-growing, relatively short-lived [< 30 years]) bivalves is also positively correlated to temperature.
There are a number of advantages of this new tool over existing paleothermometers: (i) in the studied microstructures and species, the morphological properties (size, thickness, elongation) of the biomineral units are strongly linked to temperature (also predicted by thermodynamics); (ii) the new temperature proxy can be applied to well-preserved (microstructurally unchanged) fossils even if the original chemical signature has been lost due to diagenetic alteration; (iii) once the image processing software has been trained to recognize the biomineral units, measurements can be carried out quickly.
In the second study (Milano et al. 2016a), Ms Milano evaluated possible effects of ocean acidification on the shell microstructure of C. edule. Specimens were raised at different pH levels, ranging from 900 µatm CO2 (pH 7.8) to 24,400 µatm CO2 (pH 6.4). However, even at the lowest pH, no significant changes to the size or shape of the biomineral units were detected, and growth rates remained invariant. Conversely, a strong correlation was found between biomineral size and mechanical properties of the shells. Shell portions formed during summer had larger biomineral units and fewer organics and were softer than those formed during the cold season (smaller biomineral units, more organics). Compressive stress is apparently largely absorbed by interstitial organic macromolecules.
This research clearly demonstrated that C. edule can cope well with ocean acidification, since neither growth rate nor the mechanical properties of the shells were affected by increased carbon dioxide levels in the water.
In her third study (Milano et al. 2016b), Ms Milano ESR moved into the field of archaeology. She studied the effects of thermal treatment on the shell of the gastropod, Phorcus turbinatus which is frequently found in archaeological shell middens. For this experiment, modern shells were boiled at 100°C and roasted at 300, 500 and 700°C for 20 and 60 min. Whereas boiling did not modify the shell, increasing roasting temperatures gradually deteriorated the shell integrity, changed the mineralogy and shifted the oxygen isotope ratios to lower values. Results of this study are of great value for shell midden research, because new proxies are now available which provide important information on food processing techniques and subsistence strategies of ancient societies. Furthermore, the observed microstructural and chemical changes can be used to infer the degree of diagenetic overprint which a sediment experienced in which shells were embedded.
In her last study (Milano et al. 2017b), Ms Milano studied the effects of temperature and food supply on the crystallographical and microstructural properties as well as the pigment concentration in shells of Arctica islandica. As in the previous studies, she used the scanning electron microscope and image processing techniques to quantify changes of the shell architecture at the nanometer and micrometer-scale. In addition, Ms Milano determined the crystallographic orientation of the biomineral units and the pigment concentration using confocal Raman spectroscopy. This research showed that neither the microstructure nor the pigment concentration is influenced by food quantity and type. However, temperature changed the crystallographic axes. The next step is to quantify such changes by using electron backscatter diffraction analysis and establish a crystallography-based temperature proxy.
The main ARAMACC supervisor at JGU Mainz, Prof. Dr. Bernd R. Schöne, also published a concise review paper on the use of bivalve shells as biomonitors of heavy metal pollution of aquatic environments in a renowned international peer-reviewed journal. In this article, a special focus is placed on high-resolution, precisely dated records of pollution that can be used to monitor bioavailable contaminants and determine baseline conditions in aquatic environments prior to human perturbation. Both is crucial for successful conservation and environmental restoration efforts.
Reference
Schöne BR and Krause RA 2016. Retrospective environmental biomonitoring – Mussel Watch expanded. Global Planetary Change 144, 228-251.
WP 4 (part 2) – Commercial/regulatory aspects of sclerochronology
WP 4 part 2 focused on exploitation of sclerochronological data in the commercial and regulatory sectors. It consisted of a single project, carried out by two experienced researchers (ERs) and was based at a single beneficiary:
ER 4.1(a) Juliane Steinhardt, based at HAL Aberdeen.
ER 4.1(b) Lars Beierlein, based at HAL Aberdeen.
The first appointment, Juliane Steinhardt, left the position after 13 months for personal reasons, and she was replaced by Lars Beierlein.
WP4 part 2 was focused on the development of the use of sclerochronological techniques as monitoring tools of use to the commercial and regulatory sectors. ER4.1 was to interface between the commercial and academic sectors to maximize the potential commercial exploitation of long-lived bivalves in environmental monitoring by identifying new sampling strategies, identifying new species for sclerochronological analysis and identifying opportunities to apply crossdating and geochemical techniques in existing and ongoing environmental contracts.
Progress in this area is inevitably incremental, and the response by companies to suggestions that they use new techniques tends to be based on consideration of any potential profit. The main task of ER4.1 was to write a report on existing uses of shell material for environmental monitoring and the potential for new techniques that could enhance this application and make it more robust. The principle outcome was a paper and a number of talks at influential conferences including ICES and Arctic Frontiers.
ARAMACC Training (work packages 5 & 6)
ARAMACC training consisted of seven training events (three workshops, two summer schools and two research cruises with a training element).
Summer School #1 (SOS Bangor 16th – 23rd May 2014)
The first ARAMACC training event was held in the sclerochronology department of School of Ocean Sciences at Bangor University. Like all the training events, this summer school consisted of paired modules in generic skills and specialist techniques. The generic skills section introduced the students to principles of research management and included training in: 1) Effective management of personal research activity; 2) Health and Safety; 3) how to maximise benefit from host supervisory teams and from secondments at other partners; 4) research ethics; 5) Intellectual Property Rights (IPR); 6) awareness of the wider scientific context.
The specialist module focused on the fundamental techniques of chronology building using shells: the construction of crossdated chronologies using multiple shell growth increment series. It included training in: 1) Health and Safety issues associated with shell sectioning (including sectioning and use of chemicals); 2) selection of suitable shells for analysis (key metrics, shell condition, preliminary 14C dating); 3) methods of shell preparation (sectioning, grinding, polishing, , embedding in resin, acid etching, acetate peel replicas, thin-sectioning, staining); 4) measurement of annual growth increments using image analysis software; 5) detrending methods (negative exponential, splines, Regional Curve Standardisation); 6) software tools for chronology construction (COFECHA, Shellcorr, Arstan); 7) chronology statistics (eg Expressed Population Signal); 8) statistical techniques for environmental reconstruction using instrumental series (eg calibration-verification).
We were especially pleased to welcome a distinguished visiting researcher, Valerie Trouet, from the Laboratory of Tree-Ring Research at University of Arizona. Professor Trouet demonstrated the strong links between sclerochronology and the established field of tree-ring research, as well as showing the use of KNMI Climate Explorer for analysing proxy-environment links.
Science at sea #1 (Research cruise to the Hebrides and St Kilda with RV Prince Madog) 27th May – 3rd June 2014
The purpose of this cruise was to collect dead and live Glycymeris glycymeris and Arctica islandica from various sites off NW Scotland for use in building shell-based chronologies for ESR1.3 with the ultimate goal of obtaining a multi-centennial record of the variability of the Scotland-Norway branch of the North Atlantic Current (NAC). Shells were collected from Skye, Canna and St Kilda.
Key skills training was provided in: 1) Health and Safety at sea; 2) deployment and operation of oceanographic equipment, geophysical equipment (side-scan sonar) and bottom-sampling equipment (grab samplers, multi-corers, gravity corers, dredges); 3) sample screening and subsample selection; 4) sample preservation and curation techniques; 5) appropriate onboard communication with the scientist-in-charge and other scientists and with the ship’s master, officers and crew; 6) ethical issues associated with the collection of live animals.
Science at sea #2 (Research cruise to the Faroe Islands and Viking Bank with the Norwegian research vessel GO Sars) 8th – 14th November 2014
The purpose of this cruise was to collect dead and live Glycymeris glycymeris and Arctica islandica from sites around the Faroe Islands and the Viking Bank for use in building shell-based chronologies for ESRs1.1 and 1.2 with the ultimate goal of obtaining a multi-centennial record of the variability of Atlantic inflow to the Norwegian Sea. Shells were collected from sites to the southeast and southwest of the Faroe Islands, and from several sites on Viking Bank.
Key skills training reprised that provided during Science at sea #1, although in this case all the ESRs were present on the cruise.
Workshop #1 (Held at JGU Mainz 14th – 20th March 2015)
The fourth training event (and first workshop) was held in the Institute of Geosciences at Johannes Gutenberg Universität in Mainz.
In this case, the generic skills module was devoted to scientific writing and publication, with the aim of providing training in publication options (print and online), journal selection, manuscript preparation and submission, and the peer review system. The students worked from their own manuscripts, preparing them for publication and “reviewing” each others’ manuscripts. Invited speaker Thierry Corrège, Editor-in-Chief at Palaeogeography, Palaeoclimatology, Palaeoecology gave an informed talk on the current world of scientific publishing.
The scientific skills module focused on geochemical techniques used in sclerochronology. Participants brought their own samples and learnt various techniques for shell preparation and analysis. All the fellows were able to obtain practical experience of one or more of the geochemical analysis systems available at the Institute, including Continuous Flow-Isotope Ratio Mass Spectrometry (CF-IRMS), Inductively coupled plasma atomic emission spectroscopy (ICP-OES) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS).
Workshop #2 (Held at NIOZ Texel 26th October – 2nd November 2015)
The fifth training event was held in the Royal Netherlands Institute for Sea Research (NIOZ), situated on the Dutch island of Texel.
This workshop started with the specialist skills section, which was devoted to the ecology of long-lived bivalves. The aim of this module was to provide training in the ecological and biological contexts of growth increment formation. We had talks by Marc Lavaleye from NIOZ on ecological adaptation of bivalves and by Julien Thébault from UBO Plouzané on taxonomy, followed by a practical exercise on bivalve identification. Bryan Black, the visiting scientist from University of Texas at Austin, led a challenging exercise on multivariate analysis in ecology, including the use of sclerochronological datasets in multivariate analysis. As a final treat, Chris Richardson from SOS Bangor led a field exercise, sampling the common cockle Cerastoderma edule from nearby tidal flats. The samples were later eaten at the home of one of the students.
The generic skills part of this workshop concentrated on the funding landscape and how to attract funding. Students were trained in grant and proposal writing, peer-reviewing of grant proposals and delivery of contractual obligations. The main part of the workshop was the writing of proposals to the “Scientific Research Council of Ruritania”, prepared by teams of 3 or 4 students.
As an optional bonus (which most of the students attended), Rob Witbaard organized a two-day workshop in the computer language “R”.
Summer School #2 (Held at IOF Split 8th – 13th May 2016)
The second summer school, and sixth training event altogether, was held in the Institute of Oceanography and Fisheries in Split, Croatia.
The generic skills section of this summer school focused on dissemination, communication and public outreach. Here, participants received training in the range of media that are available for communication of science (including social media and broadcast media), presentation of science at outreach events, oral presentations to general audiences and involvement in legislative and advisory bodies. The school included live practice in interviewing techniques and an entertaining talk by Ana Bedalov, who had organized the Research Night in Split the previous year. Examples of the hazards and delights of working with the media were presented by Michael Carroll, James Scourse and Paul Butler. Thanks to local contacts, news items on the school appeared on Croatian TV and in the local press.
This was followed by the specialist part of the school, which was devoted to the link between sclerochronology and numerical modelling. The aim was to introduce the students to the use of sclerochronological time series as a tool for constraining and validating numerical climate models. This section featured talks by invited speaker Paul Halloran from University of Exeter, and by ARAMACC participants Odd Helge Otterå and Eduardo Zorita. Participants were able to compare their data with model data. Some proxy-model connections were made which, after a bit more analysis, might lead to some interesting results.
Workshop 3 (Held at Akvaplan-niva, Tromsø 24th – 30th January 2017)
The final (seventh) ARAMACC training event took place in Tromsø, northern Norway, and was linked to the Arctic Frontiers (AF) 2017 conference. AF is a transdisciplinary initiative that links research, policy and business in the context of the Arctic Ocean. It holds an annual conference in Tromsø in late January around the time when the sun first appears above the horizon after the long Arctic winter. There were three parts to this event:
1. Before the AF conference sessions, a Retreat Day (24th January) was organized by Michael Carroll. This took place at the Wilderness Centre (Vilmarkssenteret) outside Tromsø and included good food and drink, dogsledding in the snow, and a full day of reflection on the project and discussion of future developments.
2. The final ARAMACC conference was merged into AF 2017, where all the ARAMACC fellows were allocated talks or poster presentations.
3. After the conference, the ARAMACC fellows joined the AF Young Scientists Forum (YSF), which took place on the coastal Hurtigruten cruise and at Svolvær in the Lofoten Islands. The final ARAMACC training module (“Entrepreneurship, commercial exploitation and career development”), was merged into the YSF. This included talks on career development and interviewing techniques (Melita Peharda), the use of scientific data in the context of the oil and gas industries (Geir Morten Skeie), and the links between science and entrepreneurship (K. Tønnesen Busch). In addition, the YSF included a wide range of talks on cultural matters relating to the Arctic, as well as ARAMACC-led talks on sclerochronology from northern Norway (Al Wanamaker) and on Holocene marine climate reconstructions (Carin Andersson Dahl).
4. PhDs and postdocs
ESR 1.1 Fabian Bonitz PhD defence expected in spring 2018.
ESR 1.2 Tamara Trofimova PhD defence expected in spring 2018.
ESR 1.3 Stella Alexandroff PhD defence expected in summer 2018.
ESR 1.4 Amy Featherstone defended her PhD (successfully, subject to satisfactory revisions) on June 29th 2017. She has subsequently accepted a 10-month position at Åarhus University, Denmark, which began in October 2017. She plans to apply for Marie Curie postdoctoral funding to continue her work in Åarhus after the position finishes.
ESR 1.5 Juan Estrella-Martìnez PhD defence expected in summer 2018.
ESR 2.1 Maria Pyrina submitted her PhD thesis to the University of Hamburg on 27th March 2017(within three years of starting) and successfully defended her PhD on 16th June 2017.
ESR 3.1 Irene Artero Ballesta is aiming to defend her thesis early in 2018 During the 4th year required for a PhD in the Netherlands she is being supported with funding from NIOZ.
ESR 3.2 Ariadna Purroy Albet successfully defended her PhD on March 17th 2017 at the Institute of Oceanography and Fisheries, Split. Subsequent to the end of her contract she has returned to Barcelona, Spain and is currently passing through the administration procedure related to the recognition of her PhD degree in her home country.
ESR 4.2 Liqiang Zhao successfully defended his PhD thesis on March 13, 2017 and received a “summa cum laude” for both the oral part of the thesis and the dissertation. Since the end of his employment through ARAMACC funds, Dr. Zhao has worked as a postdoc at JGU Mainz. In December 2017, he will return to China where he has accepted a permanent Assistant Professorship position at the Institute of Oceanology of the Chinese Academy of Sciences, located in Qingdao. His future research will focus on the ecology and biology of marine bivalves and the implemention of sclerochronological techniques that he acquired and developed at the University of Mainz.
ESR 4.3 Stefania Milano successfully defended her PhD thesis on December 13, 2016 (less than three years after starting, and received a “summa cum laude” for both the oral part of the thesis and the dissertation. Her dissertation thesis was recently awarded a prestigious research prize by the Freunde der Universität Mainz e.V. (http://www.gnk.uni-mainz.de/240.php). Since the end of her ARAMACC contract in March 2017, Dr. Milano has been working as a postdoc with Dr. Gernot Nehrke in the Marine BioGeoscience group at the Alfred Wegener Institute in Bremerhaven on the mineralogical and nanostructural transformation of shell carbonate in relation to thermal diagenesis. Recently, Dr. Milano successfully applied for two year research stipend by the DFG (Deutsche Forschungsgemeinschaft). At the same time, she received an offer by the Max Planck Institute for Evolutionary Anthropology for a six-year postdoctoral fellowship with Prof. Jean-Jacques Hublin, Dr. Klervia Jaouen and Dr. Kate Britton (Department of Human Evolution) which starts in October 2017. The project focuses on stable isotope analyses of Pleistocene shell remains excavated from different paleoanthropological sites in Europe to reconstruct local environmental conditions.
5. Workshop participation and other achievements
ESR 1.1 Fabian Bonitz and ESR 1.2 Tamara Trofimova participated in an ICES working group (WKGIC2) on “Growth-increment chronologies in marine fish: Climate-ecosystem interactions in the North Atlantic”, held in Esporles, Mallorca 18th - 22nd April 2016.
ESR 1.3 Stella Alexandroff spent time at the 14Chrono Centre at the Queen’s University Belfast headed by Prof. Paula Reimer, where she was trained in sample processing and radiocarbon analysis and helped to prepare her own samples for radiocarbon dating.
ESR 1.3 Stella Alexandroff and ESR 1.5 Juan Estrella-Martìnez participated in the summer school “Isotopes in Climate and Earth Systems” on Islay, Scotland, in August 2015 organised by the Bolin Centre/Stockholm University.
Stella Alexandroff was also:
1) a steering committee member of the CNS Women’s Network at the College of Natural Sciences, Bangor University. The women’s network aims to act as a platform for networking opportunities that promote gender equality;
2) PhD course representative at the School of Ocean Sciences, Bangor University, from October 2014 to October 2016;
3) Part of the Athena SWAN self-assessment team of the School of Ocean Sciences, Bangor University. Stella contributed to the school’s application for an Athena Swan Bronze Medal, which is an award given to higher education and research institutions for their efforts to ensure gender equality in employment.
ESR 3.1 Irene Artero Ballesta took part in a number of training events and symposia related to the field of Dynamic Energy Budget modelling:
1) 8-th international tele-course on DEB 2015+ training part in Marseille, France (February 19- March 26 and from April 20 - April 27, 2015.
2) 4th Symposium on DEB theory: Marseille, France (April 28-30, 2015)
3) 5thInternational Symposium on DEB theory (Tromsø) + DEB School, Tromsø : May 21- June 2, 2016
6. Project website
www.aramacc.com
This website is currently maintained by Paul Butler (p.butler@exeter.ac.uk)