CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Deliverables
Summary:
In contrast to Arcachon Bay the Sacca di Goro has a more limited tidal flushing and nitrogen inputs per unit area are greater by a factor of ca. 6. Important blooms occur of Gracilaria sp. and Ulva rigida and dystrophic crises occur on an annual basis. Peak values of Ulva biomass reach 800 g DW/m2 compared to a maximum of 150-200 g DW/m2 of Z. noltii in the Bassin d'Arcachon and a maximum of 400 g DW/m2 of Ruppia cirrhosa in the Valli di Comacchio. The system is net autotrophic during the growing season of the macroalgae, and becomes net heterotrophic during the algal crash which results in a dystrophic crisis. Inorganic nutrient concentrations in the water column show a negative correlation with plant biomass and a positive relation with riverine inputs. This shows that Ulva biomass represents clearly a temporal sink of N and P, but these elements are recycled during the algal crash. Very high concentrations of iron (200-500 µmol.cm-3) occur in the sediment of the Sacca di Goro. The seasonal changes in the HS- - FeS - FeS2 system were monitored. As in the Bassin d'Arcachon, the total ratio of acid volatile sulphides to Fe(II), which is an indication of the saturation of the sedimentary iron buffer to sulphide, was always below 1.
Summary:
The living Zostera noltii plants establish strong links with the bacteria in the rhizosphere. The rhizomes and roots of this phanerogam present a habitat for sulphate-reducing and nitrogen fixing bacteria (Donnelly et al., & Finster et al., Extended Report, Vol. I, p. 179- and p. 149, respectively), and most of the nitrogen fixation is actually due to sulphate reducing bacteria in this environment (Welsh et al., 1996, Marine Biology 125, 619). The surface of the rhizomes supported young and mature biofilms which showed a patchy colonisation pattern, while surface colonisation was much less extensive (and mainly concentrated around wounds) on roots. Furthermore, diatoms were observed on the surface of roots and rhizomes. Longitudinal sections of roots showed the unequivocal presence of bacteria within the root tissues, but no bacteria were found in the interior of the rhizomes (Donnelly et al. & Finster et al., Extended Report, Vol. I p. 179- and p. 149, respectively). It was found that 4 % of the sulfate reduction and 35 % of the nitrogen fixation of the total benthic system.
Summary:
Iron-bound phosphate represents less than 1 % of total phosphate. A major fraction is bound to calcium (e.g., calcium hydroxy apatites). Mobilisation of calcium bound phosphorus is stimulated by protons and organic acids formed by fermentation processes; this might play a role in reducing sediments (Stal et al., 1996). However, in recent experiments it has been shown that phosphate release was only slightly stimulated by amending anoxic sediment slurries with glucose. The most probable explanation for this result was that protons and organic acids produced during fermentation were quickly consumed by sulfate-reducing bacteria (Schaub & Stal, Extended Report, Vol. I, p. 307). Organic phosphate was a major fraction in the vegetated site (57 %) and less important at the non-vegetated site (7 %). Hence, plant biomass and detritus represent a major temporal sink for phosphorus and we have studied remineralisation of organic phosphorus and the importance of bacterial phosphatases in this process. Interestingly, alkaline phosphatase activities were very low at the non-vegetated site and higher, albeit patchily distributed, at the vegetated site. On average per cm-3, vegetated sites yielded 4 to 5 times more culturable viable bacteria showing phosphatase activity than non-vegetated sites (Donnelly et al., 1998, Progress Report p. 51).
Summary:
"Buffering capacity" has been defined in ecology as a holistic concept (see Jørgensen, 1992), but we have shown that it can also be investigated using mechanistic studies.This concept has enabled a dialogue to be established between holistically and mechanistically oriented researchers, and is particularly useful to study non-linear changes in coastal lagoon ecosystems. We have applied this concept to understand "local stability" in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. The Bassin d'Arcachon is still an outstanding environment which harbours the largest meadows of the seagrass species Zostera noltii Hornem. (70 km2) in Western Europe. Nevertheless, a critical evaluation of nutrient loading through the tributaries has shown that nitrogen inputs continue to rise, while phosphorus loadings have drastically decreased since the early 1980's after the implementation of urban wastewater treatment schemes (data courtesy of IFREMER, Arcachon and l'Agence de l'eau Adour-Garonne).
Summary:
We have found that high iron availability in the sediment, i.e. 50 - 100 µmol.cm-3 (see also Giordani et al., 1996, Stal et al., 1996 in Hydrobiologia 329, final report of the EU project CLEAN, EV5V-CT92-80), buffers efficiently against increased biogenic sulphide production related to increased eutrophication. A novel system, the biological oxygen and sulphide monitor (BOSM) has been developed for monitoring the fate of sulphide amended to sediment slurries and for measuring the reoxidation of sulphide by abiotic processes and chemotrophic bacteria in sediment slurries under both aerobic and anaerobic conditions (Heijs et al., 1999, reproduced in Extended Report, Vol. I, p. 115-). A first approximation of the sedimentary buffering capacity to sulphide is given by the maximum amount of sulphide added before free sulphide is detected in the sediment slurry medium. The initial products of added sulphide comprise mainly iron sulphide (FeS), which was the only product at station A (outer marine influenced station), while at station B (inner station) sulphur and pyrite were additional products in the surficial and deeper layers, respectively (Heijs et al., 1999).
Summary:
The biodiversity of the prokaryotes in the rhizosphere of Z. noltii was studied in detail by application of molecular techniques. A 16-S RNA clone library was constructed from 16 S RNA isolated and amplified from the 1 to 2 cm depth layer (Cifuentes et al. a, Extended Report, Vol. I, p. 49-). The library is composed of 57 bacterial sequences of which 54 were unique. The most abundant group are the delta-Proteobacteria and comprise sequences related to sulphate reducers (40 % of total bacterial sequences). This is a very high percentage showing the quantitative importance of sulphate reducers in this environment. However, none of the extracted sequences from the natural environment corresponded to sequences of sulphate reducers isolated from this environment by classical cultivation techniques (Cifuentes et al. a,b, Extended Report, Vol. I, p. 49 and Vol. II, p. 531).
Summary:
Because heterotrophic bacteria have much lower C/N ratios than detritic plant material, its mineralisation may create a bacterial demand for mineral N. This possibility was studied in microcosm experiments; two different scenarios of primary producer mineralisation were studied: i.e., Zostera marina roots as representative of rooted phanerogam communities, and Ulva lactuca thalli as typical for eutrophied coastal lagoons. The enrichment of the sediment with root material from Zostera marina as well as with Ulva lactuca thalli stimulated the oxidation of organic carbon and bacterial growth as compared to the unamended sediment (Lomstein et al. a,b, Extended Report, Vol. II, p. 371, p. 379). In contrast to the surface addition of Ulva lactuca, which stimulated the fluxes of phosphorus and ammonia from the sediment surface to the water column (Lomstein et al.a, Extended Report, Vol. II, p. 379), Zostera marina root addition into the sediment increased the retention of ammonium compared to carbon. Hence, it was confirmed that additions of Zostera marina roots to the sediment resulted in increased bacterial ammonium assimilation rates thus making inorganic nitrogen less available (at least temporarily) for plant growth. Hence, the effect is a reduction of the effect of external N-loading (Lomstein et al.b, Extended Report, Vol. II, p. 379).
Summary:
We found that the Zostera noltii meadows support a habitat for a diverse gastropod and copepod fauna. The copepod fauna comprises both species specialised to live on the Zostera leaves as well as strictly meiobenthic species (Antajan, 1998 DEA thesis Université Bordeaux 1). A transect was studied from a dense Z. noltii vegetated site to a bare sandy sediment, linking microelectrode measurements with meiofaunal studies. In the Z. noltii beds a deeper oxygen penetration correlated with a higher meiofaunal biodiversity compared to the bare sandy sediment site (Colangelo et al., Extended Report, Vol. I, p. 273). Sulphide tolerance of the dominant benthic copepod species Mysochra pontica is intermediate between those found for species from sandy sediments and those found for typical thiobenthic representatives from euxinic sediments. The effects of sulphide and hypoxia were studied in detail for the different life cycle stages of the copepod Acartia tonsa (Invidia et al., Extended Report, Vol. II, p. 509)
Summary:
Both in Italy and in France we have worked in close co-operation with potential end-users, viz. the Amministrazione Provenciale di Ferrara and the Conseil Général du Département de la Gironde, respectively. Therefore, we have developed methods to use as indices for determining the susceptibility of lagoons to oxygen deficiency and dystrophic crises. A classification system based on a combination of different variables measured during the growth and decay phases of the dominant primary producers, i.e., net maximum community productivity (NP), dark respiration (DR) of oxygen, sediment oxygen demand (SOD), dark sulphide release from sediments (DSR), sediment acid volatile sulphide (AVS) and reducible iron. The classification based on NP, DR and DSR only provides coarse information but enables a rapid assessment of the balance of community oxygen metabolism and the intensity of disturbance and/or resistance against dystrophy. The classification based on SOD/SRR and AVS/Fe gives more sensitive information on sediment buffering capacities, but is biased by the large spatial heterogeneity of the individual variables (Viaroli et al.). Also a simple measurement of nitrogen fixation in the seagrass fields allows to asses the impact of nitrogen loadings.
Searching for OpenAIRE data...
There was an error trying to search data from OpenAIRE
No results available