Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery
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Grant agreement ID: 226273
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Conserving Europe's water bodies
Grant agreement ID: 226273
1 March 2009
29 February 2012
€ 9 022 069,24
€ 6 984 092,85
Final Report Summary - WISER (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery)
WISER stands for “Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery’ and supported the implementation of the Water Framework Directive (WFD) by developing tools for integrated ecological status assessment of European surface waters, with a focus on lakes and transitional/coastal waters. Further, it evaluated and predicted the effects of restoration and management on recovery processes in rivers, lakes and transitional/coastal waters. Both themes, assessment and management/restoration, considered the potential impacts and implications of global and climate change.
Altogether 118 existing databases from previous research and monitoring initiatives were compiled and provided an excellent basis for the analysis of pressure-impact relationships and of management-recovery relationships. This data source was supplemented by an extensive field campaign to generate data from 33 lakes and eight transitional/coastal waters addressing assemblages of the aquatic flora and fauna in these waters, together with accompanying environmental variables. The field campaign thereby allowed of sampling different locations at different times of the year, thus enabling the estimation of uncertainty of assessment due to spatial and temporal variability within the ecosystems. This approach also allowed for an estimation of the researcher-dependent component of uncertainty, for instance due to methodological issues or varying determination skills.
Extensive reviews of the existing restoration/management literature supplemented the few existing databases on the effects of restoration and management in all ecosystem types. This data was used to identify environmental implications of pressure reduction (e.g. reduced nutrient loads in lakes) and restoration (e.g. hydromorphological enhancement in rivers), and to estimate biological recovery. Time series from selected case study catchments finally provided the basis for the estimation of the effects of climate warming in all ecosystem types.
With regard to biological assessment of lakes and transitional/coastal waters, WISER refined existing and developed new indicators for all biological assemblages addressing two main stressors: eutrophication (including hypoxia in coastal waters) and hydromorphological degradation (including water level fluctuations in lakes). The new indicators were subject to an uncertainty analysis based on a new software WISERbugs (WISER Bioassessment Uncertainty Guidance Software). WISER supported the Intercalibration Exercise and developed a series of common intercalibration metrics for different assemblages, in particular for the intercalibration of lakes. WISER experts also assisted intercalibration on meetings of all related Geographical Intercalibration Groups during the lifetime of the project, to advise intercalibration and to ensure the development of practical metrics and approaches.
Based on literature reviews and meta analysis of >700 research studies, conceptual models were developed to structure and summarise the existing knowledge about pressure-impact and management/restoration-recovery effects in rivers, lakes and transitional coastal waters. These models will help river basin managers to estimate the effects of restoration and mitigation measures, but also help identify potentially ineffective measures that have been rarely proven to be ecologically successful. Models of the impact of global warming were developed to inform water management practitioners about the potential implications of water temperature increase on the structural (taxonomic) and functional composition of assemblages. The results can help estimate the species’ losses and gains in particular regions as well as the effects on the reference conditions of assessment indices and metrics (e.g. feeding types).
All WISER results have been made available through the project website www.wiser.eu which, amongst other products, provides access to 88 deliverables, detailed animated lists of all lake and marine waters sampled for the field campaign, several software tools for taxa data entry and uncertainty analysis, a methods database comprising information of >300 European water body assessment systems, a meta database with information about 118 existing project and monitoring databases, and a book of abstracts to the Final WISER Conference in Tallinn (Jan. 2012). Almost 150 publications resulted from WISER or are in an advanced stage of preparation. The main outcome of the project has been summarised as key messages, which can be viewed on the project’s homepage.
Project Context and Objectives:
Europe is rich in aquatic ecosystems, which have been impacted in the past decades by an equally variable range of environmental pressures, such as pollution and modification of the physical habitats. Recent European policies target a good ecological status for all surface waters, i.e. water bodies need to be assessed by comparison with a reference quality target. If the quality is below the target, which is the case for the majority of water bodies in Europe, they need to be restored until the target status is being achieved. For many aquatic ecosystem types, ecological assessment systems have been developed already and River Basin Management Plans outline the required restoration and management measures to achieve the target.
In spite of these requirements, many countries, however, had not completed the development of new WFD-compliant systems for assessing ecological status. Classification systems for several relevant combinations of BQEs, ecosystem type and stressor were missing in 2009 and the impact of some stressors (in particular hydromorphological degradation) on the biota was widely unknown, in particular for lakes and transitional/coastal waters. There was also very little information on the uncertainty associated with most assessment systems and the comparability of status assessments between Member States. Furthermore, there was insufficient knowledge on how biological assemblages (“Biological Quality Elements”, BQEs) recover from degradation and respond to climate change, thus limiting the predictability of the success of future restoration endeavours.
These obvious gaps in assessment techniques and guidance were addressed by the WISER consortium, whose partner institutions covered all major regions of Europe and provided profound expertise in lake, river, transitional and coastal water ecological research. In particular, WISER scientists applied a variety of analytical and modelling techniques to addressed the following research questions:
• Which biological indicators are best suited for the assessment of aquatic ecosystems? Which are most reliable? Which are redundant? This aim is limited to lakes (with a special focus on hydromorphological degradation) and coastal and transitional waters.
• How can assessment results obtained with different BQEs or from different sites best be compared, intercalibrated and combined into an integrated appraisal of ecological status?
• How do BQEs recover from degradation, in particular hydromorphological degradation and eutrophication, and how is assessment and restoration affected by climate change?
• How (un)certain are ecological status assessment results and predictions of the outcome of management measures? How can uncertainty be quantified and consequently minimised?
WISER was composed of five scientific modules, plus two modules on coordination and dissemination. The module ‘data and guidelines’ (Module 2) was mainly a supporting module, compiling all the data accessible to the project, closing gaps in the data sources, storing the data generated in the project’s field campaigns, providing tools for data queries and data entry, evaluating and comparing existing assessment methods, and developing common guidelines for indicator development. Workpackage 2.1 developed the WISER central database to store all data from the field campaigns in 2009 and 2010 in a standard format. The Workpackage assisted the analytical Workpackages with tailor-made queries to generate specific sub-sets of data for analysis. Workpackage 2.2 provided guidance on the development of new indicators. This Workpackage also reviewed the state-of-the-art of bioassessment in European countries.
Two modules addressed ‘Ecological indicators for assessment and intercalibration’ in lakes and transitional/coastal waters. The lake module (Module 3) was dealing with four BQEs used for lake assessment: phytoplankton, macrophytes, benthic invertebrates and fish. It developed and improved state-of-the-art assessment methodologies, taking into account the remaining needs to complete intercalibration of assessment systems. As each BQE was investigated within an own workpackage, concerted effort was spent on in-depth evaluation of this BQE, its various relationships to environmental stressors and its sensitivity to spatial and temporal variation. The latter was subject to an extended uncertainty analysis, with strong support by an own Workpackage dedicated to the analysis of the impacts of various sources of uncertainty in aquatic assessment (see below). Among the stressors, hydromorphological degradation was in focus, as knowledge about the effects of this stressor was very sparse. Furthermore, Modules 3 and 4 also aimed to fill the remaining gaps in the assessment of eutrophication.
A similar approach was followed in Module 4 targeting transitional and coastal waters. It addressed four BQEs (phytoplankton, macroalgae/angiosperms, benthic invertebrates and fish) and aimed to fill the existing gaps in assessment methodologies for this water body category. In addition to analyzing existing data, a field campaign was run in 2009 and 2010 to generate the data required to develop new assessment metrics and to estimate their uncertainty due to their sensitivity to spatial and temporal variation.
The results of both assessment modules not only assisted water body assessment and monitoring in Europe, but also supported the comparison of assessment results within the intercalibration exercise. Thus, Module 3 and 4 worked in close collaboration with the Geographical Intercalibration Groups (GIGs). In particular, WISER partners attended all relevant GIG meetings to present the status of WISER results. In return, GIG experts were invited to WISER Workpackage and general assembly meetings, to ensure a high level of applicability of WISER results.
The impacts of pressure reduction (i.e. management and restoration) and climate change on the ecological status in all water categories were addressed by Module 5. The module explored recovery processes of the biota in rivers (Workpackage 5.1) lakes (WP5.2) and coastal/transitional waters (WP5.3) and analysed the potential effects of different climatic conditions on ecological status and recovery. For lakes and marine ecosystems the focus was on (re-) oligotrophication, whereas the effects of hydromorphological degradation were analyzed for rivers, and additionally considered for lakes. All Workpackages in Module 5 also developed conceptual models of the effects of management/restoration on assemblages and their characteristics (functions, e.g. feeding types). In concert, Module 5 provided guidance for river basin management, on the ecological effectiveness of management and rehabilitation measures and on the potential positive/negative affects of climate change on ecological status and recovery from degradation.
Module 6 synthesized the results on water body assessment, restoration and climate change. The Workpackages focused on uncertainty (Workpackage 6.1) the comparison of different BQEs (WP6.2) the comparison of stressor-response relationships (WP6.3) and the comparison of management/restoration-recovery relationships (WP6.4). Workpackage 6.1 not only provided individual guidance on uncertainty estimation for all partners in Modules 3 and 4, but also produced uncertainty estimation software. A particular focus in Workpackage 6.2 was to estimate the consequences of the application of the ‘one-out-all-out’ rule in water body assessment (i.e. applying the worst case scenario and take the worst of several assemblage results as the final result). The remaining Workpackages 6.3 and 6.4 compared the responses of different biological quality elements to different stressors and stressor reductions (management/restoration) in different water categories. Module 6 provided scientific support to the design of monitoring programmes and tested methods on how to best integrate results for single BQEs into a holistic assessment of water bodies.
Finally, a module on ‘dissemination’ (Module 7) was responsible for maintaining the project website www.wiser.eu and for providing concise and up-to-date information on the project for water managers, scientists and the general public. Workpackage 7.1 was responsible for the communication within the WISER consortium, which was implemented by setting up an Intranet and video-conferencing tools. The Intranet provided the platform for internal communication and the exchange of data and documents. Furthermore, Workpackage 7.1 aimed to establish and maintain a vital communication with WISER end users, i.e. river basin managers and members of Geographical Intercalibration Groups. Another Workpackage (7.2) was specifically dedicated to the organisation of the final WISER conference, which took place in January 2012 in Tallinn.
This structure of WISER into Modules and Workpackages not only ensured an effective and timely elaboration of tasks, but also helped achieve a large degree of integration of the results. This process was coordinated within Module 1 (Coordination), but largely organised within the WISER Steering Group composed of two members of the coordinating organisation (University of Duisburg Essen) and of all leaders of Modules 2–7. Monthly electronic meetings and bi-annual physical meetings of the steering group ensured an effective organisation of the workflow, a timely and adequate response to problems reported by consortium members and a democratic process to take important decisions.
All WISER results were presented to the end users during the final conference and were made available on the public part of the website.
In terms of products, WISER resulted in:
• 88 deliverables (some of which are currently subject to a peer-review process at various scientific journals and, thus, available only with restricted access to stay in line with the publication policies of the journals; this will be changed to full access in due time after approval)
• 108 publications until the termination of the project; further publications are planned in course of two more journal special issues (one has already appeared), amongst others a special issue in Hydrobiologia comprising about 25 papers on the main WISER results (release probably in late 2012/early 2013
• biological and environmental data from two field campaigns (2009, 2010) in 33 lakes and 8 transitional/coastal waters
• a large project data base with environmental and biological records of all kinds of surface waters in Europe
• a meta database with metadata of 118 recent European research projects (FP5–FP7) and national monitoring activities
• a methods database with metadata of >300 surface water classification systems from 29 European countries (covering all BQEs and water categories)
• conceptual models of pressure reduction and recovery in rivers, to help practitioners estimate effects and non-effects of restoration
• a taxa entry tool to generate taxonomically correct taxa lists of all aquatic assemblages
• common metrics and metric fact sheets to inform and guide end users about the suitability of metrics for intercalibration of individual national assessment results at the large scale
• a LakeLoadResponse software tool to estimate effects of nutrient reduction in lakes (LLR)
• a software tool to estimate the uncertainty in water body assessment due to spatio-temporal and methodological variability (WISERBUGS)
• a Book of Abstracts of the WISER Final Conference in Tallinn (25–26 January 2012)
• an interactive web-tool to derive existing knowledge about cause effect chains in river restoration
• a series of key messages to the water managers to translate the major WISER outcome and provide guidance for water management
• a series of public newsletters to disseminate WISER’s achievements among the general public
Data and guidelines (Module 2)
Intercalibration is a fundamental prerequisite to compare the results of hundreds of bio-indicator systems in Europe
European countries currently use nearly 300 different methods to classify the ecological status of their surface waters. The methods mainly consider species abundance and sensitivity and focus on the impacts of organic pollution and eutrophication. The intercalibration exercise aimed at harmonising the national classifications in order to provide common denominators for the comparison of individual national results within a European context of ecological status classification. The WISER project reviewed 297 assessment methods, based on a questionnaire survey sent to water authorities in all Member States and additional countries, which are being implementing the Water Framework Directive (Figure 1).
Figure 1: Results and distribution of the characteristics of the 297 national assessment methods reported by 28 countries and reviewed by the WISER project (based on a questionnaire survey sent to water authorities in all countries implementing the Water Framework Directive).
The pressure-impact relationships were tested empirically for two-third of the methods, mostly for rivers, lakes and coastal waters, while the methods for transitional waters were least validated. The strength of the relationships differed significantly between organism groups and water categories. The correlation coefficients generally covered a broad range (<0.4 to >0.8). The strength of the relationship decreased in order: Phytoplankton > macroscopic plants > benthic invertebrates > phytobenthos and fish fauna, and for the water categories in order: Coastal waters > lakes > transitional waters > rivers. Status boundaries were mostly defined using statistical approaches.
The overview of the WFD intercalibration exercise revealed that the assessment methods for the following biological elements are almost fully intercalibrated: Phytoplankton and macrophytes in lakes, and benthic invertebrates, phytobenthos and fish fauna in rivers. Intercalibration has not been fully completed for the remaining biological elements / surface water types.
The multitude of aquatic bioassessment methods used for the assessment of the European surface waters is perplexing. It is questionable if the methodological patchwork allows for comparable ecological status classification across Europe. Nevertheless, the WFD intercalibration exercise has provided methodology to check the comparability of results and consistency in classifications. However, despite of more than 10 years of development, there are not fully set of methods for all quality elements in all categories of surface waters. Also the intercalibration still need to be continued in the future to ensure comparability of new methods and improvements of the existing methods.
The outcomes of the pressure-impact analyses conducted to test the national methods are promising, but more effort is needed in order to develop a comprehensive understanding of the human pressures detected by the individual methods. In particular there is a need to better understand cause (human pressure) - effect (metrics or indicators) relationships for highly integrative biological elements such as fish or plants. Such models would help to choose the right management actions to improve the quality of the vegetation and fish fauna that are important for people using lakes, rivers and coastal waters for recreation and fishing.
The boundaries in the ecological classifications were not often based on ecological principles. The ecological targets are generally based on statistical distributions rather than on meaningful ecological changes in ecosystem functions and in the biological communities. The challenge remains to incorporate ecological components and functions into the national systems of ecological water quality classifications.
Birk, S., Bonne, W., Borja, A., Brucet, S., Courrat, A., Poikane, S., Solimini, A. G., van de Bund, W., Zampoukas, N., Hering, D. (2012). Three hundred ways to assess Europe’s surface waters: an almost complete overview of biological methods to implement the Water Framework Directive. Ecological Indicators, 18, 31-41.
Birk, S., Bonne, W., van de Bund, W., Poikane, S., Zampoukas, N. (2012). Europe's quest for common management objectives of aquatic ecosystems. In: Schmidt-Kloiber, A., Hartmann, A., Strackbein, J., Feld, C.K. Hering, D.: Current questions in water management. Book of abstracts to the WISER final conference - Tallinn, Estonia, 25-26 January 2012: 28-29. (Downloadable file available at http://www.wiser.eu/meetings-and-events/final-conference/abstracts/)
The WISER Central Database as a tool for future research
A large number of datasets from rivers, lakes and coastal waters have been compiled and stored in the WISER Central Database (CDB). Data for all biological quality elements and all water categories are available from the CDB in a harmonised format. More specifically, the CDB can be used to combine (1) biological data with environmental pressure data (chemistry etc.), (2) data for different biological quality elements, (3) data from different water categories. These data are accessible both for WISER partners and for other scientists. The conditions for use of WISER data depend on the intellectual property rights (IPRs) stated by each data owner. Detailed information on all WISER datasets, including IPR information, is available in the WISER metadatabase.
Figure 2: Geographical coverage of the WISER Central Database (CDB). Countries represented in the CDB are coloured blue. Coloured pie sectors indicate data from lakes (lilac), coastal/transitional waters (brown) and rivers (pink) (white = not available).
The WISER Central Database contains biological and other environmental data from 26 European countries (Figure 2). The WISER field campaign in 2009/2010 resulted in ca. 8000 biological samples from ca. 1000 sampling stations in lakes and coastal/transitional waters from 14 countries, containing altogether 40 000 records of species abundance. In addition, the CDB contains existing datasets from previous research projects, national monitoring etc., containing more than 1 500 000 records of species abundance and 900 000 other environmental observations from ca. 75 000 sampling stations in rivers, lakes and coastal/transitional waters. This extensive database can be very useful also for future research related to river basin management, as well as more general research in e.g. aquatic ecology, biodiversity and environmental stressors.
Information on the WISER Central Database:
Moe, S.J. R. Brænden, B. Dudley, A. Schmidt-Kloiber, J. Strackbein. The WISER way of organising ecological data from European rivers, lakes and coastal waters. Hydrobiologia (in prep).
Schmidt-Kloiber, A, B. Dudley, J. Strackbein, R. Vogl, S.J. Data about data – the WISER metadatabase. Hydrobiologia (in prep.).
Angeler D.G R. K. Johnson, D. Hering, S. J. Moe. Cross-taxon responses to stress gradients in streams and lakes. Hydrobiologia (submitted).
Ecological indicators for assessment and intercalibration: lakes (Module 3)
The reliable assessment of the impact of different lake stressors requires the use of different Biological Quality Elements
Different Biological Quality Elements (BQEs) are being used to assess the ecological status of lakes in Europe: fish, benthic invertebrates, macrophytes/phytobenthos and phytoplankton. The different responses of these BQEs to different stressors require the use of several BQEs in order to assess the multiple impacts by multiple stressors. In brief:
• Phytoplankton and macrophytes show strong responses to eutrophication pressure.
• Littoral benthic invertebrates clearly respond to morphological shoreline degradation, and macrophytes to water level fluctuations.
• Fish assemblages show less clear signals to individual pressures, but may be good indicators of climate warming.
Table 1: Overview of general stressor-response relationships of lake Biological Quality Elements as a result of the WISER lake module (indicated as correlations according to Pearson’s R2 or Spearman’s rho).
BQE Pressure and indicators Best common metrics R2 Rho
Phytoplankton Eutrophication (TP) Chlorophyll-a
PTI (taxonomic composition) 0.63
Macrophytes Eutrophication (TP) ICM (taxonomic composition)
HyMo (water level fluctuations) WLi (taxonomic composition) (NO+FI) 0.77
Benthic fauna (littoral) Eutrophication MMI 0.40
HyMo (shore modifications) MMI (LIMCO) (DE+DK)
MMI (LIMHA) (DE+DK) 0.70
Fish fauna Eutrophication MMI (CPUE< BPUE, OMNI) 0.25
Phytoplankton is highly sensitive to eutrophication pressure, based on the statistical analyses using all regional data sets (Table 1). The best common metric, with high sensitivity, is the Phytoplankton Trophic Index, which includes both taxonomic composition data as well as chlorophyll a. These two metrics have been combined into a common metric for the intercalibration of phytoplankton methods with successful results in both the Northern GIG and the Central-Baltic GIG. Cyanobacterial blooms are common in all eutrophied lakes across Europe. The risk that the WHO health alert threshold for cyanobacteria biovolume (1-2 mg/l) would be exceeded is 10% at a total-P concentration of 20 µg L-1 and 30% at 40 µg L-1. The best metric for macrophytes indicating eutrophication pressure is the intercalibration common metric for taxonomic composition (ICM; Table 1), which has also been used for intercalibrating macrophyte methods in the same GIGs.
Other metrics for phytoplankton and macrophytes responding to eutrophication have also been tested within WISER, such as cyanobacteria abundance and macrophyte growing depth. These metrics also show highly significant relationships with nutrient pressures and may be easier to communicate to the public and water managers. A shift from macrophytes to cyanobacteria highlights an important functional shift that can greatly affects the use of freshwaters for recreation, swimming or as a reservoir for potable water.
Table 2. Overview of metric sensitivity to pressures for biological quality elements in lakes resulting from the WISER lake module. GIG = Geographical Intercalibration Group. CB GIG = Central European and Baltic region, NGIG = Northern region, MGIG = Mediterranean region. GAM = generalised additive model. The other regressions are linear models. N = number of lake-years. Sensitivity has been assessed from regression analyses of dose-response curves along pressure gradients using large-scale pan-European datasets from > 1000 lakes from 21 countries.
Metric Metric description Pressure r2 GIG or country p N
Chla Chlorophyll a Eutrophication (Total-P) 0.63 All, but mainly NGIG & CBGIG <0.001 16949
PTI Phytoplankton Trophic Index Eutrophication (Total-P) 0.67 (GAM) All, but mainly NGIG & CBGIG <0.001 2287
Cyano bloom intensity Cyanobacteria biovolume Eutrophication (Total-P) 0.34
(GAM) All, but mainly NGIG & CBGIG <0.001 1710
SPI Size Phytoplankton Index Eutrophication (Total-P) 0.23
0.19 CB GIG
M GIG <0.0001
MFGI Morpho-Functional Group Index Eutrophication (Total-P) 0.33
0.38 CB GIG
M GIG <0.0001
FTI Functional Traits Index (mean of SPI and MFGI) Eutrophication (Total-P) 0.39
0.50 CB GIG
M GIG <0.0001
J’ Evenness Eutrophication (Total-P) 0.19
0.07 N GIG
CB GIG <0.001
ICM Intercalibration Common Metric Eutrophication (Total-P) 0.52 All, but mainly NGIG & CBGIG
EI Ellenberg Index of taxonomic comp. Eutrophication (Total-P) 0.47 All, but mainly NGIG & CBGIG
Cmax Maximum colonization depth (abundance proxy) Eutrophication (Total-P)
0.58 All, but mainly NGIG & CBGIG
WIc Water level Taxonomic comp index Hydromorphological changes (water level fluctuations in ice-covered lakes) 0.77 NGIG (NO+FI) 26
MMI Multimetric Index Eutrophication (Total-P) 0.40 (whole lakes) CB-GIG <0.001 161
MMI Multimetric Index Morphological alterations and Eutrophication (shore line modifications, land use and TP)
MMI Multimetric Index Morphological alterations (shore line modifications)
0.49 All, mainly CBGIG
LIMCO Littoral Invertebrate Multimetric Index based on Composite Sampling Morphological changes of lake shore 0.70*
LIMHA LIMI based on Habitat-specific Sampling Morphological changes of lake shore 0.72*
MMI Multimetric Index consisting of BPUE, CPUE and OMNI Eutrophication
(non-natural land cover) 0.25 All <0.001 445
BPUE Biomass per unit effort Eutrophication
(non-natural land cover) 0.19 All <0.001
CPUE Catch per unit effort (number of individuals) Eutrophication
(non-natural land cover) 0.18 All <0.001 445
OMNI Relative number of omnivorous individuals Eutrophication
(nonnatural land cover)
*Value represents Spearman’s rank correlation coefficient Rho; in four bio-geographical regions where different metrics correlated best with the stressor index.
Macrophytes also responded clearly to hydromorphological pressure, in terms of water level fluctuations in regulated lakes in the Northern countries. The macrophytes water level fluctuation index (Wlc) has a clear threshold response concerning the indicator taxa e.g. Isoetes corresponding to ca. 3.5 m water level fluctuations. Thus, this metric is a very promising tool to define ecological potential in heavily modified water bodies.
Littoral macroinvertebrates respond clearly to modification and degradation of shoreline habitats in lakes. Two new multimetric indexes have been developed within WISER, including several single metrics, such as the number of taxa of mayflies, stoneflies, caddisflies, water beetles, mussels, dragon-flies, relative abundance of the functional groups like gatherers or collectors, or classes of chironomids, and Margalef diversity. Number of Macroinvertebrate species and fraction of individuals feeding on particulate organic matter were lower at both intermediately and strongly modified lake margins than at unmodified margins in 64% of 44 lakes. Another multimetric index based on littoral macroinvertebrates also responds to a combination of pressures from eutrophication and morphological modifications (Table 2).
For fish, the best metrics to assess eutrophication impacts are biomass per unit effort (BPUE) (r2 = 0.19) catch per unit effort (CPUE) (r2 = 0.18) and relative number of omnivorous individuals (OMNI) (r2 = 0.18) but none of these have been used for intercalibration of national methods. Fish has however been shown to respond to climate warming with cold-water species like arctic char being pushed further north and towards higher altitudes, while warm-water species like many cyprinids increase in dominance and widen their bio-geographical range. Small-sized individuals dominated warm lakes, whereas in cold lakes the relative proportion of large-sized fish increased. The dominance of small fish in warm lakes was primarily the consequence of an increase in juvenile fish.
Operational monitoring and assessment of ecological status in lakes should be based on the most sensitive quality elements to different pressures. WISER evidence supports that the botanical BQEs (phytoplankton and macrophytes) are well suited to assess lake eutrophication impacts. Effects of measures to restore eutrophied lakes can only be seen when the total phosphorus concentration is reduced to less than 100 µg/l. For hydromorphological pressure, macrophytes respond well to water level fluctuations in northern regulated lakes and may thus be used as a tool to set environmental goals for heavily modified water bodies. Littoral macroinvertebrates have been shown to sensitively assess impacts of morphological alterations to lake shores. Fish should be monitored to assess impacts of climate warming.
Brauns, M., Garcia, X.-F. N. Walz & M.T. Pusch 2007. Effects of human shoreline development on littoral invertebrates in lowland lakes. Journal of Applied Ecology, 44, 1138-1144
Emmrich, M., Brucet, S., Ritterbusch, D., Mehner, T., 2011. Size spectra of lake fish assemblages: responses along gradients of general environmental factors and intensity of lake-use. Freshwater Biology 56: 2316–2333
Kolada A, Hellsten S, Søndergaard M, Mjelde M, Dudley B, van Geest G, Goldsmith B, Davidson T, Bennion, H, Nõges P & Bertrin V, WISER Deliverable D3.2-3: Report on the most suitable lake macrophyte based assessment methods for impacts of eutrophication and water level fluctuations. March 2011.
Mischke U, Carvalho L, McDonald C, Skjelbred B, Lyche Solheim A, Phillips G, de Hoyos C, Borics G, Moe J & Pahissa J. 2011. WISER Deliverable D3.1-2: Report on phytoplankton bloom metrics, March 2011
Pedron, S., De Bortoli, J, Argilier, C., Fish indicators for ecological status assessment of lakes affected by eutrophication and hydromorphological pressures. WISER Deliverable D3.4-4.
Phillips G, Skjelbred B, Morabito G, Carvalho L, Lyche Solheim A, Andersen T, Mischke U, de Hoyos C & Borics G. 2010. WISER Deliverable D3.1-1: Report on phytoplankton composition metrics, including a common metric approach for use in intercalibration by all GIGs, Aug 2010.
Jeppesen, E., Mariana Meerhoff, Kerstin Holmgren, Ivan Gonza´lez-Bergonzoni, Franco Teixeira-de Mello, Steven A. J. Declerck, Luc De Meester, Martin Søndergaard, Torben L. Lauridsen, Rikke Bjerring, Jose´ Maria Conde-Porcuna, Ne´stor Mazzeo, Carlos Iglesias, Maja Reizenstein, Hilmar J. Malmquist, Zhengwen Liu, David Balayla, Xavier Lazzaro, 2010. Impacts of climate warming on lake fish community structure and potential effects on ecosystem function. Hydrobiologia (2010) 646: 73–90.
Ecological indicators for assessment and intercalibration: coastal/transitional waters (Module 4)
A new phytoplankton size spectra index (SSI) for the assessment of transitional waters
A multi-metric index of the size spectra sensitivity of phytoplankton (ISS-phyto), which integrates the size structure metrics with metrics describing the sensitivity to anthropogenic disturbance, Chl a and species richness was developed. The index was found to produce significantly higher values at undisturbed than disturbed sites and thereby being a promising indicator to assess the status of phytoplankton communities.
Relatively few indices have been proposed for the assessment of the community structure changes of coastal and transitional water phytoplankton. Morphological-functional traits of phytoplankton with different cell size and size spectra show a specific response to different types of anthropogenic pressures. Nevertheless, very few attempts have been given so far to utilise functional traits such as body size, at the individual level, or size spectra, at the guild or community level, to develop multi-metric assessment tools compliant with the WFD.
We have developed, tested and validated a multi-metric index of size spectra sensitivity of phytoplankton (ISS-phyto), which integrates size structure metrics with metrics describing the sensitivity of size classes to anthropogenic disturbance, Chl a and species richness measures. The ISS-phyto was developed using phytoplankton data of 14 Mediterranean and Black Sea transitional water bodies (i.e. coastal lagoons), which were classified as either “disturbed” or “undisturbed” ecosystems based on expert quantitative analysis, evaluation of anthropogenic pressures in the catchment area and their current protection and conservation status. The index was found to discriminate between natural and anthropogenic pressures presenting significantly higher values at undisturbed than disturbed sites; it has then was also tested successfully to a different set of lagoon and coastal areas in the WISER field studies.
The new metric ISS-phyto is a promising tool for assessment of the response of the phytoplankton community on eutrophication pressure in transitional and coastal waters and is recommended for further testing as a WFD monitoring tool in coastal lagoons.
Lugoli F., Garmendia M. , Lehtinen S., Kauppila, P., Moncheva S., Revilla M., Roselli L., Slabakova N.,Valencia V. , Basset A., 2012. Application of a new multi-metric phytoplankton index to the assessment of ecological status in marine and transitional waters. Ecological Indicators (submitted)
Vadrucci, M.R. Stanca, E., Mazziotti, C., Fonda Umani, S., Reizopoulou, S., Moncheva, S., Basset A., 2012. Ability of phytoplankton trait sensitivity to highlight anthropogenic pressures in Mediterranean lagoons: a size spectra sensitivity index (ISS-phyto) (in preparation)
Benthic invertebrates respond consistently to human pressure gradients across transitional and coastal waters
Several different indices have been proposed and may be used to classify the status of benthic invertebrates in transitional and coastal waters, and in lagoons. However, the response of such methods to human pressure gradients is critical in accepting them as suitable tools in assessing the ecological status within the WFD. Until now, very few studies investigated such response of methods already accepted within the WFD.
We investigated 13 single metrics (abundance, species richness, Shannon’s diversity, AMBI, five ecological groups, Margalef index, SN, ES100, and ES50) and eight multimetric methods (ISS, BAT, NQI, M-AMBI, BQI, BEQI, BITS, and IQI) to assess coastal and transitional benthic status along human pressure gradients in 5 distinct environments across Europe: Varna bay (Bulgaria), Lesina lagoon (Italy), Mondego estuary (Portugal), Basque coast (Spain) and Oslofjord (Norway). Within each system, sampling sites were ordered in an increasing pressure gradient according to a preliminary classification based on professional judgement, and the response of single metrics and assessment methods to different human pressure levels was evaluated. The different indices are largely consistent in their response to pressure gradient, except in some particular cases (i.e. BITS, or ISS, in some cases). Inconsistencies between indicator responses were mostly in transitional waters (i.e. IQI, BEQI), highlighting the difficulties of the generic application of indicators to all marine, estuarine and lagoon environments. However, some of the single (i.e. ecological groups approach, diversity, richness, SN) and multimetric methods (i.e. BAT, M-AMBI, NQI) were able to detect such gradients both in transitional and coastal environments.
The agreement observed between different methodologies and their ability to detect quality trends across distinct environments constitutes a promising result for the implementation of the WFD’s monitoring plans.
Borja, A., E. Barbone, A. Basset, G. Borgersen, M. Brkljacic, M. Elliott, J. M. Garmendia, J. C. Marques, K. Mazik, I. Muxika, J. M. Neto, K. Norling, J. G. Rodríguez, I. Rosati, B. Rygg, H. Teixeira, A. Trayanova, 2011. Response of single benthic metrics and multi-metric methods to anthropogenic pressure gradients, in five distinct European coastal and transitional ecosystems. Marine Pollution Bulletin, 62: 499-513.
Zoobenthos species traits are useful and reliable for the assessment of transitional water ecosystems
Structural taxonomically-based components of the benthic macroinvertebrates communities have been used to assess ecological status (sensu WFD) of lagoon ecosystems. Few studies have utilised functional traits such as body size, at the individual level, or size spectra, at the guild or community level, to develop multimetric assessment tools compliant with the WFD.
We have developed, tested and validated a multi-metric Index of Size Spectra sensitivity (ISS), which integrates size structure metrics with metrics describing the sensitivity of size classes to anthropogenic disturbance and species richness measures. The ISS was developed using benthic macroinvertebrates data of 12 Mediterranean and Black Sea transitional water bodies (i.e. coastal lagoons), which were classified as either “disturbed” or “undisturbed” ecosystems based on expert quantitative analysis, evaluation of anthropogenic pressures in the catchment area and their current protection and conservation status. Data from a thirteenth Mediterranean lagoon, characterised by a very strong abiotic stress gradient, were used for validation purposes. The index is effective to discriminate between natural and anthropogenic pressures presenting significantly higher values at undisturbed than disturbed sites.
The new metric proposed for transitional waters is a precise and sensitive tool for discriminating various levels of ecosystem disturbance and easy to apply. The ISS has more practical advantages than disadvantages (Table 3), which favour its widespread use as a monitoring tool in coastal lagoons.
Basset, A., Barbone, E., Borja, A., Brucet, S., Pinna, M., Quintana, X.D. Reizopoulou, S., Rosati, I. Simboura, N., 2012. A benthic macroinvertebrate size spectra index for implementing the Water Framework Directive in coastal lagoons in Mediterranean and Black Sea. Ecological Indicators, 12: 72-83.
Table 3: List of advantages and disadvantages of the Index of Size Spectra Sensitivity (ISS).
A1. Strong theoretical background on body size responses to environmental stress D1. Damages to individual body size during sampling and/or handling
A2. Strong theoretical background on size spectra D2. Some taxa are particularly sensitive to sampling, fixation and handling
A3. Body size is easy to measure D3. Sampling probability of large sizes is affected by the sampling effort
A4. Body size measurements do not require high level of expertise D4. Size spectra are sensitive to size-selective predation pressures
A5. Inter-calibration of body size measures among laboratories is simple D5. Taxonomic expertise is anyway required (but see also point A7.)
A6. Consistent pressure-impact relationships are available for the most common pressures D6. Assessment of individual body size is time and cost-expensive
A7. Size spectra detect early signals of anthropogenic disturbances before responses are detectable at the taxonomic level -
A8. High discrimination power of
anthropogenic pressures, even without accounting for taxonomic richness
A9. High robustness to natural variability, embodied in the size spectra
Fish indicators respond consistently to human pressure gradients across transitional waters
Using a matching combination of fish index, reference values and local dataset, the transitional fish index (and metrics) can be sensitive to pressure gradients. There is a proven negative response of fish quality features to pressure gradients, which make them suitable for biological quality assessments of transitional waters.
A conceptual analysis, carried out on the strength of expected metrics responses to a set of human pressures, suggested chemical pollution and loss of habitat as the type of pressures more frequently and more strongly related to fish metrics. These pressures are often regarded as important indirect causes of alterations in transitional water fish assemblages. This preliminary analysis provided the conceptual basis for the ranking of human pressures in order of expected relevance to fish in transitional waters. In order to confirm further the relationship between fish-quality attributes and pressures, two WFD-compliant indices (the AFI and the EFAI in use for assessment in the Basque country (Spain) and Portuguese estuaries, respectively) were related to a set of pressures acting in these water bodies, while also considering their hydro-morphological descriptors. Stepwise linear multiple regression analysis indentified the following best model relating AFI index scores (as the dependent variable) to explanatory (independent) variables. The model identified a mixture of relevant pressure and hydromorphological covariates and indicates that, in this case, the deeper the estuary, and the shorter the residence time, the pressure index and the channelled ports within the estuary, then the higher the AFI values would be, indicating higher ecological quality. AFI clearly decreases with the increase of pressure proxies and morphological pressures. Similar analysis for the EFAI found comparable negative response of the index scores with increasing values of pressure proxies (see figure below). In this case, the EFAI responded to the overall anthropogenic pressure level.
Furthermore, the good results of the intercalibration (IC) exercise suggests that each fish tool included in that analysis is in fact reacting in a common manner to a same level of human pressures, and providing a good agreement between methods in the diagnosis of ES. This is the ultimate goal of using fish in ecological assessments and suggests that all inter-calibrated indices are relevant and valuable indicators of human pressures in their own right. That is, there are providing an indication of ES independently of the pressure proxies used in the development and calibration steps.
In addition to the regression approach, an alternative method to establish metric-pressure relationship using a Bayesian approach was test-trialled in Drouineau et al. (2012). The Bayesian method allows the ability both to select relevant fish metrics and to combine them taking into account their sensitivity to pressure, their variability or any other relevant feature. For example, the method can also be a way to integrate data from expert opinion and it finally gives an assessment of the uncertainty of the diagnostic tool. It was tested on a dataset composed of a sample of 14 French lagoons. The analysis suggests that the quality diagnostics are less variable at the level of the multi-metric indicator than at the level of the fish metrics considered individually.
Fish response to pressure fields in transitional waters provides a high level of ecological integration to the quality evaluation of transitional water systems. The Fish BQE is a sensitive indicator of ES and will be valuable to identify those specific pressures affecting fish assemblages providing targets for minimising the effects of stress in mitigation and restoration plans. Whole indices provide more consistent overall ES assessments but fish metrics considered individually may be more useful as a means to focus restoration measures.
Aubry A, Elliott M (2006) The use of environmental integrative indicators to assess seabed disturbance in estuaries and coasts: Application to the Humber Estuary, UK. Mar Pollut Bull 53:175-185
Drouineau H, Lobry J, Delpech C, Bouchoucha M, Mahevas S, Courrat A, Pasquaud S, Lepage M (2012) A Bayesian framework to objectively combine metrics when developing stressor specific multimetric indicator. Ecological Indicators 13:314-321
Borja A, Uriarte A, Muxika I, M. GJ, Uyarra MC, Courrat A, Lepage M, Elliott M, Pérez-Domínguez R, Alvarez MC, Franco A, Cabral H, Pasquaud S, Fonseca V, Neto JM (2012) Report detailing Multimetric fish-based indices sensitivity to anthropogenic and natural pressures, and to metrics’ variation range. In: WISER Deliverable D44-3
Pérez-Domínguez R, Alvarez MC, Borja A, Cabral H, Courrat A, Elliott M, Fonseca V, Franco A, Gamito R, Garmendia JM, Lepage M, Muxika I, Neto JM, Pasquaud S, Raykov V, Uriarte A (2012) Precision and behaviour of fish-based ecological quality metrics in relation to natural and anthropogenic pressure gradients in European estuaries and lagoons. In: WISER Deliverable D4.4-5.
Impacts of pressure reduction and climate change on the ecological status (Module 5)
Catchment and riparian land use control local habitat conditions
The hierarchical order of landscapes and riverscape implies a hierarchical order of stressors. Stressors, such as land use or river regulation, are ubiquitous in large parts of the world because of the multifaceted land and water uses. Flood protection is usually linked to severe modifications of hydrological and morphological characteristics. Agriculture increasingly dominates entire regions due to society’s growing demand for food, resources and energy.
Broad-scale stressors impose serious problems for restoration and recovery. Urban settlement and agriculture in the catchment upstream of a site largely influence and control the physical habitat conditions at the respective site (low uncertainty). Urban settlements can influence water retention and storage through the percent of impervious area in the catchment, which in turn affects the hydrograph and can lead to severe flash floods following stormwater release. Less than 10% urban settlements in the catchment are frequently reported to significantly reduce biological and ecological quality (Paul and Meyer 2011).
The major impact pathways of intensive agriculture are nutrient enrichment (eutrophication) and excessive fine sediment entries (habitat loss). While nutrient enrichment can directly affect algal and plant communities, the loss of coarse substrates affects fishes and invertebrates.
Naturally vegetated riparian buffer strips not only can buffer impacts from agriculture, but also provide habitat (woody debris, leaves), shelter (root wads, shade), food (wood, leaves, terrestrial insects) and energy (carbon and nitrogen) to the riverine assemblages (Allan 2004, Feld et al. 2011, low uncertainty).
Aquatic assemblages (e.g. fish and macroinvertebrates) significantly change their structural and functional composition, when the percent area as agriculture upstream exceeds 20% in mountain ecoregions (Figure 3) (low uncertainty). Lowland assemblages seem to respond less sharp to agriculture and significantly change values at 30–50% (medium uncertainty). These findings are in line with the thresholds reported by previous studies (e.g. Allan 2004).
Near-stream buffer areas along several kilometres upstream can help maintain biological diversity and functionality at a site, if a minimum of 40–50% within the buffer area is covered by forest (medium uncertainty). Ecological recovery may be promoted already by a minimum of 25% forested buffers upstream (high uncertainty). Yet it is important to note that the increase of forest cover alone is unlikely to mitigate the impacts of land use.
Intensive agriculture and other land uses characterise large parts of Europe and constitute potential broad-scale stressors for riverscapes and its ecology. This in particular applies to the agricultural lowlands of Eastern, Central and Western Europe. Without appropriate mitigation and management, the negative impacts of land uses are likely to continue to impact rivers and hence hinder recovery, irrespective of hydrological and morphological improvements. Consequently, restoration and river basin management must adequately address land use impacts. That is, restoration measures are required that i) are capable of mitigating land use impacts and that ii) address the appropriate scale of impact. Riparian buffers can be considered best practice. For instance, mixed riparian buffer strips (trees, shrubs, grass) have been proven to effectively retain nutrients and fine sediments from adjacent crop fields (see Feld et al. 2011 for a review). Buffer strips require several kilometres of length rather than tens or hundreds of metres.
Eventually, given the omnipresent character of agriculture, a re-organisation of land uses is needed and as a part of future river basin management. Conversion to less intensive land use forms in riparian areas will be most effective. This would require the reorganisation of agricultural policies in parallel.
Figure 3: Boosted regression models identified the number of Ephemeroptera-Plecoptera-Trichoptera taxa (No. of EPT) to significantly decrease with increasing arable land in the riparian buffer of mountain rivers. A sharp decrease was obvious between 0 and 20% arable land. This decreasing trend is obvious too, although with less sharp the change, for lowland rivers. Note that the fitted values for EPT richness in lowland rivers mark a short gradient of one taxon difference only. The analysis was based on ca. 200 German macroinvertebrate samples in ecoregion (ER) 9 and 14. More in-depth results including fish and macrophytes are provided with WISER Deliverable D5.1-2.
Allan, J.D. (2004). Landscapes and riverscapes: The Influence of Land Use on Stream Ecosystems. Annu. Rev. Ecol. Evol. Syst. 35, 257–284.
Feld, C.K. Birk, S., Bradley, D.C. Hering, D., Kail, J., Marzin, A., Melcher, A., Nemitz, D., Petersen, M.L. Pletterbauer, F., Pont, D., Verdonschot, P.F.M. & Friberg, N. (2011) From natural to degraded rivers and back again: a test of restoration ecology theory and practice. Adv. Ecol. Res. 44, 119–209.
Paul, M.J. and Meyer, J.L. (2001). Streams in the urban landscape. Annu. Rev. Ecol. Syst. 32, 333–365.
Restoration is more likely to be successful, if upstream physical habitat degradation and land use impacts are low
Two previous statements address the predominant role of broad-scale stressors that may act at the scale of entire (sub-) catchments and consequently may impact any site within the catchment. Accordingly, river restoration is more likely to initiate and maintain biological recovery, if such broad-scale impacts are either completely missing or being mitigated in parallel to restoration at the fine (local) scale.
There is empirical evidence (medium uncertainty) from restoration monitoring that restoration measures can initiate biological recovery, if the physical habitat conditions several kilometres upstream of the restoration are only moderately modified or in better condition. In particular the fish and macrophyte assemblages were found to be strongly influenced by habitat quality up to 10 km upstream. Macroinvertebrate ecological quality was related to shorter stretches upstream (up to 2.5 km). Empirical analyses imply that about 1 km length upstream in a moderate or better physical habitat quality might suffice to promote biological recovery (high uncertainty).
Where broad-scale stressors impact ecological quality after restoration and may hinder recovery, such stressors require mitigation. Practitioners need to know the multiple stressors that may impact restoration candidate sites. They should prioritise those stretches that are least impacted by broad-scale stressors and thus may constitute stepping-stones within a broader restoration scheme. Local restoration measures need to be integrated into restoration schemes at the broad scale.
This broad-scale and integrated restoration is well referred to by the WFD and termed ‘River Basin Management’. Yet, it seems as if this broad-scale approach deserves more attention by scientists and practitioners in order to use the limited resources available most effectively for river restoration and management.
For a detailed analysis of the effects of upstream physical habitat quality and land use conditions on ecological quality assessment at restored and unrestored sites see Lorenz in WISER’s Deliverable D5.1-2.
Climate change alters fish assemblage structure and function distribution in Europe
The Intergovernmental Panel on Climate Change predicted changes in temperature and precipitation in Europe for the periods 2020–2030 and 2050–2060. These changes are expected to greatly alter the distribution of fish, by providing more suitable habitats for species tolerating or preferring warm water, and by restricting species adapted to coldwater habitats. This implies that the reference condition baselines used to assess the ecological status of rivers based on fish would not be adequate in the future.
During the last three decades, the Alpine River Traun heated by on average 2.2 °C in August, which led to unsuitable thermal conditions for the grayling (Thymallus thymallus). The grayling population greatly decline in favour of more adapted species such as barbel (Barbus barbus, Figure 4). In lowland catchments (e.g. the Seine basin in France), the absence of possible thermal refugia in the upstream part of the catchment may amplify the risk of regional species extinctions (Figure 5).
Climate Change effects have to be taken into account in River Basin Management, for instance when using reference conditions as baselines for assessment or when designing restoration measures. If salmonid species, for example, go extinct in particular catchments, this requires consideration when setting the biological assessment reference in that catchment, or when defining the biological goals for restoration. Without consideration of Climate Change impacts, assessment runs the risk of misclassification. To evaluate such potential shifts, a monitoring network of reference sites in Europe may help inform the practitioners about potential consequences of global warming and its effects on both the biota and its abiotic environment.
Figure 4: Shift of species composition from the 1980’ies until the 2000’ies in the River Traun in relation with an increase of water temperatures (on average +2.2°C).
Figure 5. Probability of presence of the brown trout (Salmo trutta, L.) in the Seine river basin (France) derived from the species distribution models (Logez et al. 2011) for the (a) the current environment conditions, (b) projected climatic conditions for 2020-2030 and (c) for the projected climatic conditions for 2050-2060. Probabilities are computed for each stream reach of the CCM2 network (probabilities: ? 0–0.1 ? 0.1–0.2 ? 0.2–0.3 ? 0.3–0.4 ? 0.4–0.5 ? 0.5–0.6 ? 0.6–0.7 ? 0.7–0.8 ? 0.8–0.9 ? 0.9–1).
Logez, M., Bady, P. and Pont, D. (2011), Modelling the habitat requirement of riverine fish species at the European scale: sensitivity to temperature and precipitation and associated uncertainty. Ecology of Freshwater Fish 21: 266–282.
Climate warming causes profound changes in lake fish assemblages
Fish play a key role in the trophic dynamics of lakes. With climate warming, complex changes in fish assemblage structure may be expected owing to the direct effects of temperature and indirect effects of eutrophication, water level changes, stratification and salinisation. This means that warming will result in fish-mediated increase in eutrophication partly counteracting the effect of nutrient loading reduction. The response of fish to the warming in recent decades has been surprisingly strong, making fish ideal sentinels for detecting and documenting climate-induced modifications of freshwater ecosystems.
An analysis of the effect on fish assemblages to climate change and climate variability has been conducted based on long-term (10 to 100 years) data series from 24 European lakes. These lakes constitute an appropriate and tractable sample of the world’s lakes since many of them have been monitored more intensively and for a longer period of time than have most lakes elsewhere. Profound changes in fish assemblage composition, size and age structure were found during the last decades and a shift towards higher dominance of eurythermal species. The shift has occurred despite an overall reduction in nutrient loading that should have benefited the fish species typically inhabiting cold-water low-nutrient lakes and larger-sized individuals.
The cold-stenothermic Arctic char has been particularly affected and its abundance has decreased in the majority of the lakes where its presence was recorded. The harvest of cool-stenothermal trout has decreased substantially in two southern lakes. Vendace (Coregonus albula), other whitefish and smelt have shown a different response depending on lake depth and latitude, with a drastic reduction in the Estonian Lake Peipsi. Perch was apparently stimulated in the north, with stronger year classes in warm years, but its abundance has declined in southern Lake Maggiore. Where introduced, roach now seems to take advantage of the higher temperature after years of low populations. Eurythermal species such as bream, pikeperch and shad are on the increase. The climate effects have overall been larger in shallow lakes.
The fish assemblage is not only affected directly by warming and changes in the thermal stability of the lakes. Numerous recent studies and reviews indicate that warming will exacerbate existing eutrophication problems and this will in a self-amplifying manner further stimulate a shift to dominance of eurythermal species. They typically tolerate low oxygen levels and high ammonia concentrations and prevalence of small fish. A reduced ice cover period will enhance fish survival, with potential cascading effects within the food web, also reinforcing eutrophication. Therefore, we can expect an allied attack by eutrophication and warming in lakes in the future and the shifts in abundance, size and composition will be reinforced and stimulated by this process.
Diatoms and macro invertebrates respond most strongly to general degradation already at low stress levels. This renders both organism groups weak indicators of local habitat improvement in degraded catchments, i.e. both groups are unlikely react to restoration unless broad-scale impacts are being remedied. Besides general and water quality degradation, fish and macro invertebrates respond most intensively to morphological degradation, structural modification and catchment land use. Fish respond strongly to hydrological degradation, too. Hence, river fauna reveals a more intense, but not necessarily more sensitive, responses to stress, compared to the flora. Overall, aquatic macrophytes were found to be comparatively weak indicators of the stressors considered.
The most obvious alterations encompass a decline in cold-stenothermal species, in particular in shallow lakes, an increase in eurythermal species even in deep, stratified lakes. Several case studies show a decrease in the average size of the dominant species roach and perch. This also means that warming will result in a fish-mediated increase in eutrophication partly counteracting the effect of nutrient loading reduction. It also implies that it will be more difficult to obtain the good ecological status required by the WFD in lakes facing temperature changes due to global warming. The way to (partly) counteract the effect of warming is to reduce the nutrient input to lakes even further than planned under the present-day climate. The response of fish to warming during recent decades has therefore been surprisingly strong, making fish ideal sentinels for detecting and documenting climate-induced modifications of freshwater ecosystems.
Jeppesen E., T. Mehner, I. J. Winfield, K. Kangur, J. Sarvala, D. Gerdeaux, M. Rask, H. J. Malmquist, K. Holmgren, P. Volta, S. Romo, R. Eckmann, A. Sandström, S. Blanco, A. Kangur, H. R. Stabo, M. Meerhoff, A.-M. Ventelä, M. Søndergaard, T. L. Lauridsen (submitted). Impacts of climate warming on lake fish assemblages: evidence from 24 European long-term data series.
A tool helps estimate effects of nutrient load reduction under a variety of climate scenarios
Nutrient assimilation capacities of European lakes were estimated using a large data. The effect of climate warming on eutrophication proved to be positive. Thus, in warmer climatic conditions, an effective reduction of nutrients is needed to achieve a good ecological condition. A model was developed and included in the LakeLoadResponse (LLR) Internet tool, which can be used by water managers to estimate the reduction of nutrient load required at present and under changing climate conditions.
The linear mixed effects model is based on chlorophyll a data from 351 European lakes. The effect of total phosphorus, total nitrogen and water temperature on chlorophyll a concentrations varied among lake types, individual lakes within a type and individual samples within a lake. The amount of variation was significantly reduced using a linear mixed effects model for nested data. The statistical inference was based on a Bayesian approach thus giving a more realistic assessment of the effect of model uncertainty. The model is implemented in an Internet tool and has been successfully used for the planning of restoration measures in Finland.
Using the LLR tool, it is possible to test how the changes in water temperature affect the nutrient reduction required to achieve good ecological status. The LLR delivers predictions on water quality status with statistical confidence intervals to give more insight for the management actions. If combined with a map-based web service, the model can help water managers illustrate the forecasted effects in maps. For instance, the effect of fisheries management will be analyzed using extensive data from Finnish lakes in the GisBloom project (Life+, duration 2010–2013).
A description of the mixed chlorophyll a model can be derived from WISER Deliverable 5.2-4: “Internet tool (model to assess target loads) for lake managers”. Further instructions of the LLR internet tool and descriptions of the underlying models are available at http://lakestate.vyh.fi.
Lake sediments provide insight into the history of the conditions of individual lakes and, hence may assist the definition of reference conditions
Throughout Europe the majority of lakes have been modified to some extent by human activity with agriculture and sewerage being the major contributors to eutrophication, most notably since the mid-twentieth century. As a consequence, higher algal productivity has lead to filtration problems for the water industry, oxygen depletion, recreational impairment, loss of biodiversity and an overall decline in habitat quality.
Lake sediment analysis provides unique insights into the history of lake ecosystems, including evidence for the nature and timing of ecosystem change resulting from human impact. Palaeoecological methods can reveal pre-impact conditions as well as identifying any signs of recovery and have played a key role in the WFD in determining pre-enrichment reference conditions. Diatom records have proved especially valuable in this respect, largely due to their sensitivity to shifts in trophic status. In the absence of long-term chemical monitoring analysis of lake sediments can provide evidence not only of the pre-eutrophication baseline conditions, but also help track degradation and recovery pathways and thus provide a valuable tool for informing restoration programmes.
By relating fossil diatom records to modern diatom assemblages collected across wide environmental gradients, very good estimates of past lake water chemistry can be inferred and an environmental history tracked down through the sediment record. With the application of radiometric dating, the timing and rate of changes can be determined and pre-impact (reference) conditions established. In many European lakes, diatoms have provided clear evidence that the onset of eutrophication was associated with changes in agricultural practice and urban development, particularly since the mid-twentieth century.
Furthermore, where restoration programmes are underway it might be expected that the diatom record would show a reversal in the degradation pathway, but instead, diatom-based metrics often exhibit an alternative recovery pathway. This demonstrates that a reduction in one or more environmental stressors may not ultimately return a lake to reference conditions, but instead other processes such as internal nutrient loadings and climate change may determine the rate and direction of recovery.
Lake sediments provide a valuable means by which reference conditions may be established in lakes. Furthermore, environmentally sensitive organisms such as diatoms may be used to determine both the degradation and the recovery process. In terms of lake management, while it is important to be able to identify baselines it should also be recognized that recovery may not simply be the reverse process of the degradation pathway and that the reference state may perhaps never be achievable in some lakes. The evidence suggests that recovery is more predictable in deep stratified lakes than shallow lakes, where top-down processes exert a major environmental control, but that in all cases the recovery process has a long way to go before reaching pre-impact conditions.
This work highlights the important role that paleolimnological approaches can play in establishing a benchmark against which managers can evaluate the degree to which their restoration efforts are successful. Diatoms are just one of many biological groups preserved in sediments and by extending this work to use multiple assemblages it is possible to evaluate wider ecosystem responses to environmental stressors. These multi-proxy palaeoecological techniques therefore have an important role to play in assessing degradation and recovery pathways and informing lake management in order to satisfy the aims of the Water Framework Directive.
Bennion, H. and Battarbee, R.W. (2007) The European Union Water Framework Directive: opportunities for palaeolimnology. Journal of Paleolimnology, 38, 285-295.
Bennion, H., Battarbee, R.W. Sayer, C.D. Simpson, G.L. and Davidson, T.A. (2011) Defining reference conditions and restoration targets for lake ecosystems using palaeolimnology: a synthesis. Journal of Paleolimnology, 45, 533-544.
Bennion, H., Simpson, G.L. Anderson, N.J. Dong, X., Hobaeck, A., Guilizzoni, P., Marchetto, A., Sayer, C.D. Thies, H. and Tolotti. M. (2011) Defining ecological and chemical reference conditions and restoration targets for nine European lakes. Journal of Paleolimnology, 45, 415-431.
Hypoxia renders ecosystem recovery more difficult
Coastal hypoxia is increasing in the global coastal zone, where it is recognized as a major threat to biota. Hypoxia is defined as oxygen concentrations below a certain value, typically 2 ml/l or 2 mg/l, but the deleterious effects on the ecosystem already start at higher oxygen concentrations. Knowing the thresholds that fundamentally lead to a change in ecosystem functioning is important to quantify for management. Moreover, these thresholds are not static but regulated by other processes, associated with both local and global pressures on the system, particularly warming. Exceeding the critical thresholds associated with hypoxia may require even further nutrient reductions to restore a well-functioning benthic community. However, recovery from hypoxia is possible.
The literature is populated with studies documenting decreasing oxygen concentrations associated with eutrophication, and how this affects the structure and functioning of the benthic community. Many coastal ecosystems in Europe and North America have now experienced decreasing inputs of nutrients, although the expected improvement of oxygen conditions and re-establishment of benthic fauna is only observed for a few systems, e.g. Delaware River and Stockholm Archipelago (Figure 6). In these systems the recovery took decades following drastic reductions in nutrient inputs. Many other coastal ecosystems show no signs of improvement, despite reduced levels of nutrients and chlorophyll.
Figure 6: Annual mean bottom water oxygen concentrations from stations located in the Inner Stockholm Archipelago (compiled from data kindly provided by C. Lännergren, Stockholm Vatten).
Hypoxia is known to alter the biogeochemical processing of nutrients leading to feed-back mechanisms through reduced nitrification and releases of iron-bound phosphorus. Moreover, the loss of bioturbating macrofaunal organisms following hypoxia reduces the efficiency of nutrient removal processes. Therefore, hypoxia is a self-sustaining process and ecosystems should be managed to maintain oxygen levels about critical thresholds that imply a collapse of the benthic community. Coastal ecosystems can, however, recover from hypoxia, but so far this has only been observed for systems with large reductions in nutrient inputs and even so, still taking decades to recover. However, re-establishment of sound benthic communities can significantly enhance the recovery process. These experiences suggest that hypoxia introduces a hysteresis response to the nutrient pressure.
Steckbauer, A., Duarte, C.M. Carstensen, J., Vaquer-Sunyer, R., Conley, D.J. (2011) Ecosystem impacts of hypoxia: thresholds of hypoxia and pathways to recovery. Environmental Research Letters 6:025103, doi:10.1088/1748-9326/6/2/025003.
Ecological regime shifts affect seagrass pressure-indicator responses and delay recovery
Ecological regime shifts affect the response of seagrass indicators to pressures and may delay restoration of seagrass meadows upon release of pressure.
We quantified and compared benthic and pelagic gross primary production (GPP) along nutrient gradients in time and space in a shallow estuary. The estuary experienced a shift from a pristine, seagrass-dominated clear water regime with high total GPP in the early 20st century to a eutrophic, plankton-dominated regime still with high total GPP in the 1980s when nutrient loadings peaked. Recent reductions in nutrient loadings reduced pelagic GPP as expected, but the water remained unclear and seagrass abundance and GPP did not increase correspondingly. The results suggest that feedback mechanisms, such as increased resuspension of the seafloor and reduced trapping of particles and nutrients, resulting from the loss seagrasses and their associated ecosystem services delay or prevent restoration to a state with seagrass dominance.
Ecosystems do not necessarily respond linearly to changes in nutrient loadings and that the response to eutrophication and oligotrophication may follow different trajectories. Reductions in nutrient loadings to levels below those causing the decline in seagrasses may be necessary, along with initiatives to e.g. reduce the disturbance of the seafloor, in order to stimulate a return to a seagrass-dominated state.
Krause-Jensen D, Markager S, Dalsgaard T (2011) Benthic and pelagic primary production in different nutrient regimes. Estuaries and coasts. DOI 10.1007/s12237-011-9443-1
Integration and optimisation (Module 6)
Uncertainty may vary between different metrics calculated for the same BQE
Many different assemblage metrics (e.g. using various combinations of taxon tolerance values, richness, abundance, traits) can be calculated for a single BQE. The selection of candidate metrics for assessment should be informed by the residual sampling variance of individual metrics, as well as their indicator value for particular stressors. This variability can itself vary considerably among different metrics describing the same BQE.
Some comparisons could be made between alternate metrics based directly on taxonomic composition (including morpho-types) and metrics based on bio-physical (e.g. macrophyte maximum colonisation depth) or biochemical measures (e.g. chlorophyll a concentration). Results were mixed. Improved taxonomic resolution reduces uncertainty of taxonomy-based metrics: Phytoplankton PTI metric (taxonomic) showed clearly lower uncertainty than SPI metric (based on phytoplankton size groups). Replicate sampling uncertainty for chlorophyll a was low.
In general, metrics with low sampling uncertainty relative to their stressor response should be used. Metric specification is likely to need to include specification of sampling and laboratory protocols. Status assessment can be made more precise if it combines taxonomic and biophysical/biochemical measurements which show low sampling uncertainty, but metrics with high sampling uncertainty should not be used or combined.
Detailed descriptions of the data basis, analytical methods and results may be found in WISER’s Deliverable D3.1-3 (‘Report on uncertainty in phytoplankton metrics’) and D3.2-2 (‘Report on uncertainty in macrophyte metrics’). Both Deliverables are downloadable from www.wiser.eu/results/deliverables/.
Spatial heterogeneity is the main source of uncertainty when classifying ecological status using marine macrophyte indices
A wide variety of methods that use macrophyte communities for water body quality assessment fulfilling the complex requirements of the WFD have been developed by different Member States. Uncertainty analyses are a powerful tool to identify and quantify the factors contributing to the potential misclassification of the ecological status class of water bodies. When applied to different classification methods based on macrophytes, uncertainty analyses revealed that the factors related to the spatial scale of sampling (both horizontal and vertical) are the main source of uncertainty. On the contrary, the uncertainty associated to both temporal variability and surveyor is very low. In addition, the risk of misclassification also depends on the width of the status class in which the EQR score falls, with narrower range classes leading to greater probabilities of misclassification. Thus, indices which EQR range is not equally split into the 5 official quality status classes present different uncertainty levels along the EQR range.
We conducted uncertainty analyses on EQR datasets of monitoring programmes using different macrophyte-based classification methods developed by different European Member States (Norway, Denmark, Bulgaria, Spain, Croatia, Italia and Portugal). These datasets included factors representative of the key sources of variability associated with the design and implementation the monitoring programs: the spatial and temporal scales of sampling, as well as the human-associated source of error. The spatial scale of sampling accounted for an average proportion of 39±10.2% of total variance among the different indices, whilst the temporal scale and the human-associated source of error only 4.5 ± 1.5% and 2 ± 2% respectively (in mean ± SE).
This study identifies the elements of a sampling design constraining the reliability and robustness of the ecological status classification of coastal water bodies. Once the major sources of variability are known, they can potentially be minimised through the re-design of sampling schemes, through improved training by operating procedures, etc. Horizontal spatial heterogeneity must be captured by sampling at different scales, providing robust estimates of the ecological quality status classification at the water body level that minimize the risk of misclassification. Depth should remain fixed or be controlled in monitoring programs in order to minimise vertical heterogeneity, except for indices based in the depth limit of macrophyte communities. Those indices where the distance between boundary classes is not uniform across the EQR range may need to assign a greater sampling effort to water bodies whose EQR score falls within the narrower status classes, in order to reduce their associated variability and increase the confidence of the classification. In contrast, sampling frequency has little effect on the precision of ecological status estimates.
Oriol Mascaró, Teresa Alcoverro, Kristina Dencheva, Dorte Krause-Jensen, Núria Marbà, João Neto, Vedran Nikoli?, Sotiris Orfanidis, Are Pedersen, Marta Pérez, Javier Romero. Exploring the robustness of different macrophyte-based classification methods to assess the ecological status of coastal and transitional ecosystems under the WFD. Hydrobiologia.
A smart sampling design helps reduce the uncertainty in lake assessment
The sources of uncertainty in water body assessment are manifold, but in part can be subjected to methodological issues. A smart sampling design may help reduce the level of uncertainty caused by, for instance, spatial and temporal variability or by individual researcher-dependent skills. In brief:
• Phytoplankton assessment should be based on at least 6 samples from the pelagic euphotic zone with higher frequency in eutrophic lakes, especially to catch harmful blooms. Standard methods and training should be used for sampling and analyses.
• Macrophyte field method should be based on transects covering all depth zones and different habitats.
• Macroinvertebrate assessment of shoreline modifications should be based on composite or habitat specific sampling (depending on region) at various stations representing the whole range of morphological shore modification.
• Fish assessment should be based on sampling of all depth strata with many gillnets. Hydroacoustic methods provide cost-effective assessment of fish abundance.
Within-lake variability of the various BQE metrics has been assessed from new WISER data sampled in ca. 21–51 lakes in 2009. 21 lakes were sampled for all four BQEs, while additional lakes were sampled for some BQEs. Within-lake variability caused by natural spatial variation, as well as variability related to sampling and analyses, was low for phytoplankton (Table 4 and 5), although this BQE revealed a higher temporal variability related to sampling frequency. To minimize the risk of misclassification lake phytoplankton should be sampled on several occasions, although the minimum recommended frequency may vary dependent on the metric and GIG. Sampling should be more frequent in eutrophic lakes to increase the probability of catching harmful blooms.
For lake macrophytes, the metrics tested for variability is on the average 25–30% with station as the major variance component (Dudley et al. 2011). Thus, to reduce misclassification of macrophyte metrics several stations should be sampled to cover all major habitat types in the littoral zone, and sampling at each station should also cover the whole vertical extension of the littoral zone. The latter is important as nutrient enrichment reduces the growing depth of macrophytes. Assessment methods based on real hydrophytes are most sensitive to eutrophication, whereas helophytes are less affected by water quality. Helophytes should be sampled if water level fluctuation or hydromorphological changes are assessed.
Table 4: Major sources and levels of uncertainty detected for the lake BQEs within the WISER project. (Taken from Mischke et al. 2012)
BQE Major variance component Overall natural + methodological variability
Phytoplankton Temporal (seasonal) Small (< 25%)
Macrophytes Spatial Medium (30%)
Benthic fauna Spatial (station) Medium (30–40%)
Fish fauna Spatial (depth stratum) Large (> 90%)
For littoral macroinvertebrates, the major sampled variability was between sites, but this was partly (8–12%) due to consistent effects of morphological habitat modification type. Thus habitat specific sampling at various stations for each level of morphological modifications of the habitat will probably reduce the metric variability.
Table 5: Metric precision given as proportion of the total variance (i.e. within- and between-lake variance) due to within-lake variability, and major within-lake variance components for four BQEs. Metrics with the lowest within-lake variance are the most precise whole-lake metrics. For benthic invertebrates, the in-lake variance incorporates variability associated with different levels of morphological pressure. See table 2 for explanation of metrics. (taken from Thackeray et al. 2012)
BQE Metric Within lake variance (excluding temporal variability*) Major variance component (excluding temporal variability*)
Phytoplankton* Chl-a 0.04 Sub-sampling
PTI 0.12 Sub-sampling
SPI 0.35 Analyst
MFGI 0.14 Sub-sampling
J’ (Evenness) 0.31 Analyst
Cyano blooms intensity 0.06 Sub-sampling
EI 0.26 Station
Cmax 0.30 Station
NTaxa 0.37 ** Station
NTaxa EPTCBO 0.44 ** Station
%POM_HabPref 0.52 ** Station
CPUE 0.962 Single gillnets
*Temporal variability in phytoplankton is estimated to ca. 14% (coefficient of variation) for monthly sampling in some UK lakes. For more info on temporal variation and recommendations of sampling frequency, please see Mischke et al. 2012.
** includes within-lake variance of 8-12% due to margin modification type (Undisturbed ,Soft modifications, Hard modifications)
For fish the major variance component is depth stratum, implying that fish metrics should not be assessed without sampling all the depth strata in a lake. Biomass estimated from hydroacoustic methods versus that estimated from gill nets are well correlated in most lakes, except in very deep lakes (mean depth >30m) where hydroacoustic methods give higher estimates than gill nets for the deeper strata. Different BQEs and metrics require different monitoring and sampling designs based on the dominant sources of uncertainty.
For phytoplankton, the greatest source of variability is seasonal variability and analytical variability. The former can be reduced by utilising metrics based on repeated sampling during specific seasons (e.g. growth season or summer months) with higher frequency in eutrophic lakes, especially to catch harmful blooms. Minimum sampling frequency varies by metric and GIG, but should always cover the late summer period. The analytical variability can be reduced by following standard counting guidance and consistent training within Member States and across Europe.
Macrophyte field method should be based on transects covering the whole depth zone and different littoral habitats. Sampling can be restricted to hydrophytes in lakes dominated by eutrophication pressure, whereas helophytes should be sampled if water level fluctuation or hydromorphological changes are assessed. More transects are needed at both ends of the trophic gradient to reduce uncertainty in status assessment.
Macroinvertebrate assessment of shoreline modifications should be based on composite or habitat specific sampling (depending on region) at various stations representing the whole range of morphological shore modification. The calculation of the whole-lake assessment score may be supported by conducting a physical habitat survey along the whole lake perimeter, relating this to the respective biological MMI, and then calculate a weighted average of site-specific MMI scores.
Fish assessment should be based on sampling of all depth strata with many gillnets. Hydroacoustic methods provide cost-effective assessment of fish abundance.
Dudley B, Dunbar M, Penning E, Kolada A, Hellsten S, & Kanninen A. 2011. WISER Deliverable D3.2-2: Report on uncertainty in macrophyte metrics
Mischke, U., Stephen Thackeray, Michael Dunbar, Claire McDonald, Laurence Carvalho, Caridad de Hoyos, Marko Jarvinen, Christophe Laplace-Treyture, Giuseppe Morabito, Birger Skjelbred, Anne Lyche Solheim, Bill Brierley and Bernard Dudley 2012. Deliverable D3.1-4: Guidance document on sampling, analysis and counting standards for phytoplankton in lakes.
Thackeray S, Nõges P, Dunbar M, Dudley B, Skjelbred B, Morabito G, Carvalho L, Phillips G, Mischke U. 2011. WISER Deliverable D3.1-3: Uncertainty in Lake Phytoplankton Metrics, June 2011.
Winfield, I. J., Emmrich, M., Guillard, J., Mehner, T., Rustadbakken, A., 2011. Guidelines for standardisation of hydroacoustic methods. WISER deliverable 3.4-3.
The ‘one-out all-out’ principle for combining multiple BQEs into an integrated classification must be applied with caution
Although the WFD requires the use of the ‘one-out all-out’ rule in classifying the biological status of a water body, its strict application is not always recommended because of the risk of downgrading sites too easily. The ‘one-out all-out’ rule works best if the redundancy between BQEs is as low as possible.
The ‘one-out all-out’ (OOAO) is the required principle by the WFD, classifying the biological status of a water body on the basis of the biological quality element (BQE) with the worst class score. This rule is very precautionary, based on the assumption that different BQEs respond to pressures in different ways and that there is a need to protect the most vulnerable biological group. However, its strict application is not always recommended because there is a risk of downgrading sites too easily.
Simulations with artificial data demonstrated that, when combining multiple BQEs that are sensitive to the same pressures or combination of pressures, the OOAO rule produced unbiased results and good class agreement only when metrics had a low level of uncertainty (SD ?0.01) which in practice is very difficult to achieve. The reliability of the classification was already very sensitive at a moderate level of metric uncertainty (SD >0.05). An alternative rule tested for combining the same set of BQEs was the average rule, producing better results for high uncertainty metrics. However this is not in accordance with the WFD guidance, as averaging among BQEs is not recommended.
The uncritical application of the ‘one-out all-out’ (OOAO) principle could pose the danger of downgrading status class of water bodies too easily. In particular, water managers should be careful when multiple BQEs that are redundant for detecting the same pressure, or combination of pressures, need to be combined into a water body assessment. It has been demonstrated that the OOAO approach only gives acceptable and comparable results if the different BQEs are complementary, showing the effects of different pressures, on different temporal and/or spatial scales, on different aspects of ecosystem functioning. Also the level of uncertainty in the biological metrics and in the BQEs used in the assessment should not be too high and not too different between BQEs.
Restoration can only be successful when all pressures are tackled simultaneously
Multiple pressures often simultaneously affect aquatic ecosystems, so consequently restoration must address these stressors simultaneously in order to be successful. For example, both the decrease in pH and increase in ammonium concentrations are associated with acid deposition. Phosphorus and nitrogen concentrations usually increase as a result of fertiliser run-off and the reduction of current speed coupled with an increase in siltation rate are associated with river canalisation. However, pressures are often water category specific. In general, rivers integrate the adverse effects of various human activities and associated pressures within a catchment, with hydromorphological degradation predominating, lake ecosystems are mainly affected by eutrophication and shoreline modification (at the global scale) and acidification (at the regional scale), while estuaries and coastal waters comprise the ultimate sink for nutrients, contaminants and other sources of pollution originating from entire river basins and are being physically.
In most restoration projects measures are taken to reduce the primary stressor, but secondary stressors often confound recovery (see Figure 7). Confounding factors such as water quality, with particular emphasis on nutrient enrichment, large-scale hydrological change such as floods and droughts and catchment management/land use and multiple pressures cause delays or failures in aquatic system recovery.
Figure 7: Proportion of literature references relating to restoration measures taken in rivers, lakes, estuarine and coastal waters, respectively.
Recovery has not necessarily failed, but the presence of secondary pressures may have pushed response times beyond those over which monitoring is typically performed. Acidification, fisheries management, industrial pollution, non-native species and climate change were the main secondary pressures impacting de-eutrophication projects in aquatic systems. Especially, internal P loading slows down recovery in many eutrophied lakes.
Recovery depends on the type and magnitude of the pressures, especially if some are still present, and on the organism group(s) used to assess recovery. Delays in recovery can be attributed to several factors, and different water types are exposed to different combinations of pressures resulting in differences in response times.
What restoration ecology more in general, needs is:
• Definition of clear goals for restoration at catchment scale that are based on recent biological monitoring results and the actual distribution of targeted species or communities.
• Identification of best-practice restoration measures to address the specific pressures.
• Balancing all measures within a catchment in order to reach the best possible synergy effects of single component measures, and ultimately to achieve recovery of the entire catchment.
Borja, A., Dauer, D.M. Elliott, M. and Simenstad, C.A. 2010. Medium- and long-term recovery of estuarine and coastal ecosystems: patterns, rates and restoration effectiveness. Estuaries and Coasts 33: 1249–1260.
Feld, C.K. Birk, S., Bradley, D.C. Hering, D., Marzin, A., Melcher, A., Nemitz, D., Pedersen, M.L. Pont, D., Verdonschot, P.F.M. Friberg, N., Natural, F., Feld, C.K. Birk, S., Bradley, D.C. Hering, D., Kail, J., Marzin, A., Pletterbauer, F. & Pont, D. (2011) From natural to degraded rivers and back again : a test of restoration ecology theory and practice. Advances in Ecological Research, 44, 119–209.Søndergaard, M., Jeppesen, E., Lauridsen,T.L. Skov, C., Van Nes, E.H. Roijackers, R., Lammens, E. and Portielje, R. 2007. Lake restoration: successes, failures and long-term effects. Journal of Applied Ecology 44: 1095-1105.
Jowett, I.G. Richardson, J. and Boubée, J.A. 2009. Effects of riparian manipulation on stream communities in small streams: Two case studies. New Zealand Journal of Marine and Freshwater Research 43: 763–774.
Spears, B, Gunn, I., Meis, S. and May, L. 2011. Analysis of cause-effect-recovery chains for lakes recovering from eutrophication. CEH-report. Contribution to Deliverable D6.4-2.
Recovery takes time, long time
Long-term studies of recovery in rivers, lakes and estuarine and coastal waters are scarce (Figure 8). One important question before comparing time spans of recovery between water categories is the definition of ‘full recovery’. ‘Full recovery’ refers to an optimal functioning of the aquatic ecosystem under the given environmental circumstances that are not or only slightly changed by human activity. Literature for both riverine and marine systems addresses this issue (Table 6), while for many lakes in lowland areas focus is more on a shift from turbid to clear water states.
Figure 8: Proportion of literature references that reported on specific biological quality elements in river, lake and estuarine and coastal water restoration studies.
Monitoring for a large proportion of studies was < 5 to 10 years, and only a few studies (one each) in rivers and estuarine and coastal waters extended >20 years.
Table 6: Summary of time for recovery, for different biological elements and substrata, under different pressures. (Taken from Borja et al. 2010)
Pressure Substrata Intertidal/subtidal Biological elements Time for recovery
Sediment disposal Soft Intertidal Meio and macrofauna 3-18 months
Marsh restoration Soft Subtidal Fishes 1-2 yr
Oxygen depletion Soft Subtidal Macroinvertebrates 2 yr
Land claim Soft Intertidal Macroinvertebrates 2 yr
Oil-refinery discharge Soft/Hard Intertidal/Subtidal Macroinvertebrates, fishes 2-3 yr
Dyke and marina construction Soft Intertidal/Subtidal Macroinvertebrates, fishes 2-3 yr
Lagoon isolation Soft Subtidal Molluscs >3 yr
Aggregate dredging Soft Subtidal Macroinvertebrates, epifauna 2-4 yr
TBT Soft Subtidal Macroinvertebrates 3-5 yr
Dredging Soft Intertidal/subtidal Seagrasses, macroinvertebrates, fishes 2->5 yr
Sediment disposal Soft Subtidal Seagrass, Macroinvertebrates, fishes >5 yr
Eutrophication Soft Subtidal Macroinvertebrates >3->6 yr
Realignment of coastal defences Soft Intertidal Marshes and macroinvertebrates >6 yr
Fish farm Soft Subtidal Macroinvertebrates 2->7 yr
Physical disturbance Soft/Hard Intertidal/Deep-sea Macroinvertebrates, megafauna 3->7 yr
Pulp mill Soft Subtidal Macroinvertebrates 6-8 yr
Oil-spill Soft/hard Intertidal/subtidal Various 2-10 yr
Fish trawling Sand-gravel Subtidal Macroinvertebrates, fishes 2.5-10 yr
Wastewater discharge Soft Subtidal Fishes 3-10 yr
Sewage sludge disposal Soft Subtidal Macroinvertebrates 3->14 yr
Mine tailings Soft Subtidal Macroinvertebrates 4->15 yr
Marsh and tidal restoration Soft Intertidal/subtidal Vegetation, fishes, birds 5-20 yr
Wastewater discharge Soft Subtidal Macroinvertebrates, seagrasses 7-20 yr
Land claim Soft Subtidal Zostera marina >20 yr
Wastewater discharge Hard Intertidal Macroalgae >6->22 yr
Large discrepancies exist between the length of monitoring programmes and the time needed for the ecosystem to reach ‘full recovery’. Although most studies do not address ‘full recovery’, some estimates are available. Recovery after weir removal may take as long as 80 years. Recovery after riparian buffer instalment may take at least 30–40 years. In lakes, time for recovery from eutrophication varies from 10–20 years for macroinvertebrates, 2 to >40 years for macrophytes, 2 to >10 years for fish. Natural recovery from acidification takes much longer compared to recovery after liming, and like eutrophication, biological recovery is taxon specific and often decades are needed to achieve pre-disturbed conditions. Estuarine and coastal waters have long periods of recovery (>10 years), although macroinvertebrates have the potential to recover within months to <5 years though mostly take >6 years. Fish recover within one to three years, depending on the type and intensity of pressure. In general, after intense and large pressures, periods of 15–25 years for attainment of the original biotic composition, diversity and complete functioning may be needed in all three water categories.
In both rivers and lakes the success rate of restoration measures appears to be much higher for the abiotic conditions than for the biotic indicators, this is particular true for hydromorphological restoration and liming. Since eutrophication is considered also to be an important pressure in rivers and lakes, this might be a major cause of hampering recovery. In lakes internal nutrient loading often delays recovery. For rivers the response of macroinvertebrates to hydromorphological restoration is questionable; some studies have shown recovery while other studies do not possibility due to the still too high nutrient levels.
Only from monitoring of biological and environmental changes after restoration can new knowledge on recovery processes can be gained and implemented. Indeed, this information provides the opportunity for practitioners and scientists to evaluate the success and efficacy of the restoration measures. Restoration monitoring requires a tailor-made sampling design (preferably a BACI-design) that allows of sound statistical analysis according to state-of-the-art methods. Surprisingly, the BACI design is primarily applied to experimental studies. A Before-After-Control-Impact (BACI) monitoring design is considered the best approach for monitoring recovery, as only this approach is capable of detecting actual effects of restoration from other natural effects, such as seasonal or annual variability.
Bernhardt, E.S. Palmer, M.A. Allan, J.D. Alexander, G., Barnas, K., Brooks, S., Carr, J., Clayton, S., Dahm, C., Follstad-Shah, J., Galat, D., Gloss, S., Goodwin, P., Hart, D., Hassett, B., Jenkinson, R., Katz, S., Kondolf, G.M. Lake, P.S. Lave, R., Meyer, J.L. O’Donnell, T.K. Pagano, L., Powell, B. and Sudduth, E. 2005. Synthesizing U.S. River Restoration Efforts. Science 308: 636–637.
Borja, A., Dauer, D.M. Elliott, M. and Simenstad, C.A. 2010. Medium- and long-term recovery of estuarine and coastal ecosystems: patterns, rates and restoration effectiveness. Estuaries and Coasts 33: 1249–1260.
Gray, J.S. and Elliott M. 2009. Ecology of Marine Sediments: science to management. OUP, Oxford, 260 pp.
Reitberger, B., Matthews, J. , Feld, C.K. Davis, W. and Palmer, M.A. 2010. River monitoring and indication of restoration success: comparison of EU and BCG frameworks. University of Duisburg-Essen, Essen, 154 pp.
Smith, E.P. Orvos, D.R. and Cairns, J. 1993. Impact assessment using the before-after-control-impact model: concerns and comments. Can. J. Fish. Aquat. Sci. 50: 627–637.
The main impact of the WISER project was achieved through strong support to the implementation of the WFD and other related European directives and policies. The project provided European countries in major regions (Scandinavia, Central and Eastern Europe, Mediterranean) with the scientific knowledge and tools necessary for a reliable assessment of the ecological status of all surface water categories, related to both direct human-induced pressures and the effects of global and climate change. These tools will facilitate planning and adjustment of the programme of measures in the river basin management plans to ensure that the WFD objective (good ecological status) is attained in as many water bodies as possible. Overall, WISER had impact on the implementation of European water policies by:
• Developing indicator for those biological quality elements and water categories (e.g. transitional waters) that were not sufficiently developed by national research programmes or by previous EU research projects on project start (Modules 3 and 4).
• Providing harmonised assessment methodologies for a large number of water categories and BQEs, including tools to estimate their uncertainty with regard to spatial and temporal variability.
• Supporting the intercalibration exercise with suggestions on both common metrics suitable for a comparison of national assessment results at the large scale and appropriate methodologies to compare the results.
• Identifying low cost monitoring methods (e.g. through pigment sensors) and approaches for monitoring ecological status and for intercalibration of member states’ ecological status assessment systems (Modules 3 and 4).
• Guidance on restoration, by evaluating the ecological effectiveness of different alternative measures of mitigation, including impacts of climate change (Module 5).
• Linking assessment methodologies to recovery processes by analyzing, and where possible, predicting restoration success with regard to biological recovery.
• Evaluating the impact of global change (climate and land use) on the ecological status of surface waters (Module 5 and 6).
• Evaluation of the effects of different ways of combining assessment results, and their implications for restoration needs using a wide variety of modelling and statistical techniques (Module 6).
The evaluation of existing and the development of new methods assisted Member States in the selection of robust indicator metrics and aided the comparisons of similar water body types among Member States. This analysis helped identify redundancy in classification and, thereby helped identify cost-effective assessment approaches.
WISER also provided an extensive evaluation of existing methods and their applicability for WFD implementation to allow of comparable assessment of ecological status of water bodies that are consistent with the normative definitions of the Directive. The most relevant methodologies for EU-wide application led to the proposal of common metrics for intercalibration, which have been widely adopted already by Member States and Geographical Intercalibration Groups, respectively. New metrics were proposed for national assessment programmes, which are ready for application in Member States.
Many of these steps lend substantial support to the ECOSTAT working group and helped identify metrics to be recommended for standardisation in the CEN framework and subsequently to be included in the Annex V of the Directive. Eventually, WISER assisted the compilation of comparable datasets across Europe, which greatly assisted both WFD implementation and the reporting on the ‘State of the Environment’ through EEA.
WISER provided scientific support to address some of the key questions identified under the WFD CIS ECOSTAT work programme in 2008–2011, including both evaluation and recommendation of options for the finalisation of the intercalibration exercise. In addition, ECOSTAT expressed several questions related to development of classification systems, such as (1) how to specify monitoring requirements for biological parameters that are cost-effective; (2) how to apply the one-out-all-out principle at the quality element level to obtain a water body level assessment of the ecological status; (3) how to combine metrics for different habitats for whole water body assessment; (4) how to assess the confidence in ecological status classification? WISER’s outcome has provided the answers to these questions.
The Strategic Steering Group on Climate Change and Water developed approaches for climate change adaptation options for water resources management in the context of the WFD implementation. They are assisted by the ECOSTAT Working Group, particularly on issues such as climate change impacts on reference conditions and ecological quality classification of water bodies. In relation to these activities, WISER addressed the effects of climate change on overall ecological quality objectives and the assessment methodology. The WISER outcome informs water managers where adaptations to climate change impacts may require different approaches (e.g. adaptations of reference conditions) in different parts of Europe.
The development and identification of harmonised methodologies and common metrics for ecological assessment in WISER also benefited the WFD CIS working group on Reporting during the 2010 reporting guidance for River Basin Management Programmes, the guidance on the reporting of the State of the Environment.
Furthermore, the results and output of WISER had and have potential impact on several activities mandated under the WFD CIS, like the ‘WFD and Hydromorphology’, ‘Environmental objectives, exemptions and related economic issues’, and ‘Biological and chemical monitoring’, as well as the activity on ‘Climate change and water’ - all of which were considered as priorities under the WFD CIS process. WISER established the links to all of these on-going activities under the WFD CIS in 2008–2011.
The results of WP5, in particular on the impacts of land use of eutrophication and hydromorphological degradation in European rivers, lakes and coastal areas, revealed that intensive agriculture is the by far most relevant stressor for European aquatic ecosystems. This is of high relevance for the revision of the Common Agricultural Policy (CAP) and, in particular, for the CIS working group on “WFD and agriculture.”
WISER provided input to the Second European Climate Change programme (ECCP II), particularly with respect to Working Group 2 dealing with impacts and adaptation, and the sectoral stakeholder group on ‘Impacts on water cycle and water resources management, and prediction of extreme events’ that is also focusing on issues related to management of water bodies and water quality. Further, WISER supported the implementation of the EU Biodiversity Strategy, by providing information on biological indicators that reflect changes in aquatic biodiversity, but which are not currently assessed in EU-wide context, i.e. reporting of biological monitoring data from aquatic ecosystems in the EU is not yet implemented as a part of the State-of-the-environment reporting for the EEA. The metrics and biodiversity indices developed and validated for WFD purposes, and biological databases collected by the WISER (Module 2) also supported the development of harmonised biological monitoring systems for EU surface waters, that were needed, too, for the estimation of progress towards the EU biodiversity objective ‘Halting the biodiversity loss by 2010’ with respect to the aquatic ecosystems in Europe. WISER contributed to the generation of aquatic species distribution maps in Europe within the Frame of the EU FP7 project ‘BioFresh’.
WISER’s outcome on the development, testing and validation of biological indicators for the assessment of European coastal and transitional waters were communicated to relevant expert groups involved in the implementation of the EU Marine Strategy. These results largely supported the definition of ‘good environmental status’ criteria for biological features and informed about appropriate methods for monitoring and assessment of the marine coastal regions, particularly concerning the biological quality elements that are common both for the WFD and the Marine Strategy Directive (e.g. macroinvertebrates, phytoplankton, macroalgae, and angiosperms, as well as fish for transitional waters, and now also required for the Marine Strategy Directive). The investigation of combined effects of management and global change in Module 5 promoted the setting of environmental objectives for the programme of measures, particularly concerning the potential effects of eutrophication and oligotrophication on coastal ecosystems. Thereby, WISER provided a broad basis and starting point for the implementation of the Marine Strategy Directive. WISER also established links to other relevant FP7 projects addressing marine ecosystem functioning in response to the research needs of the proposed Marine Strategy (e.g. THRESHOLDS).
WISER assisted the establishment of catchment management measures and the subsequent assessment of these measures in the following ways: Firstly, the project provided guidance for planning restoration measures and goals to achieve good ecological status, while, at the same time, it was accounted for different scenarios of climate change. This was done within specific case study catchments. Secondly, the WISER provided recommendations on the optimisation of restoration and management strategies by assessing the ecological effectiveness and the suitable spatial scales of successful restoration and management.
WISER contributed to the establishment of programmes of (management/restoration) measures by compiling data on restoration success and by developing and applying models that can be used to assess the effects of restoration measures on ecological status, particularly linking the biological indicator metrics to changes in pressures (Module 5). Where possible, the costs for management and restoration were assessed, and uncertainties and the risk of failing the restoration targets were assessed to formulate recommendations on how to design or adjust management strategies with best possible impact on the ecological status. The project output also provides information on the time scales required to achieve ecological target status after management/restoration, if the objectives are being achievable at all, given the climate change that may counteract management and restoration successes.
List of Websites:
The URL of the WISER project is: www.WISER.eu. It was designed to inform the educated public, and in particular the user groups addressed by WISER (water managers, environmental agencies, Common Implementation Strategy), about the progress of the project. The project beneficiaries are listed below:
No. Name Acronym Country URL Scientific contact
1 University of Duisburg-Essen UDE Germany www.uni-due.de/hydrobiology Daniel Hering
2 Norwegian Institute for Water Research NIVA Norway www.niva.no Anne Lyche Solheim
3 Natural Environment Research Council Centre for Ecology & Hydrology NERC UK www.nerc.ac.uk Laurence Carvalho
4 AZTI-Tecnalia Foundation TECNALIA-AZTI Spain www.azti.es Ángel Borja
5 University of Hull, Institute of Estuarine & Coastal Studies UHULL UK www.hull.ac.uk Mike Elliott
6 Aarhus University - National Environmental Research Institute AU Denmark www.dmu.dk Jacob Carstensen
7 Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture IRSTEA (former CEMAGREF) France www.irstea.fr Didier Pont
8 Swedish University of Agricultural Sciences SLU Sweden www.slu.se Richard Johnson
9 European Commission Joint Research Centre EC-JRC EU www.jrc.ec.europa.eu Wouter van de Bund
10 Institute of Environmental Protection IEP Poland www.ios.edu.pl Agnieszka Kolada
11 Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Forschungsverbund Berlin FVB Germany www.igb-berlin.de Thomas Mehner, Ute Mischke, Martin Pusch
12 Finnish Environment Institute SYKE Finland www.environment.fi/syke Seppo Hellsten
13 Spanish National Research Council CSIC Spain www.csic.es Núria Marbà
14 ALTERRA Green World Research ALTERRA Netherlands www.alterra.nl Piet Verdonschot
15 University of Natural Resources and Applied Life Sciences Vienna BOKU Austria www.boku.ac.at Stefan Schmutz
16 Estonian University of Life Sciences EMU Estonia www.emu.ee Tiina Nõges
17 University College London UCL UK www.ucl.ac.uk Helen Bennion
18 Institute for Ecosystem Studies CNR-ISE Italy www.cnr.it Giuseppe Morabito
19 Deltares DELFT Netherlands www.deltares.nl Harm Duel
20 University of Coimbra, Institute of Marine Research IMAR Portugal www.imar.pt João Carlos Marques
21 Institute of Oceanology, Bulgarian Academy of Sciences IO-BAS Bulgaria www.io-bas.bg Snejana Moncheva
22 Trinity College Dublin TCD Ireland www.tcd.ie Kenneth Irvine
23 University of Salento USALENTO Italy www.unile.it Alberto Basset
24 University of Bournemouth BourneU UK www.bournemouth.ac.uk Ralph Clarke
25 La Sapienza University of Rome UNIROMA1 Italy www.uniroma1.it/ Angelo Solimini
Grant agreement ID: 226273
1 March 2009
29 February 2012
€ 9 022 069,24
€ 6 984 092,85
Deliverables not available
Grant agreement ID: 226273
1 March 2009
29 February 2012
€ 9 022 069,24
€ 6 984 092,85
Grant agreement ID: 226273
1 March 2009
29 February 2012
€ 9 022 069,24
€ 6 984 092,85