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The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002. Temperature affected plankton population selecting thermophilic ones and had direct and indirect effects on its nutritional quality given by its FA patterns. Among algae, Ceratium hirundinella dominated and occurred at higher temperatures than described in the literature. Cyanobacteria showed a limited development. Diaphanosoma brachyurum was the dominant zooplanktonic species. Thermal environment appeared to favour the dominance of cladocerans and a decline in copepods abundance with cyclopoids (Acanthocyclops robustus) favoured over calanoids. Variation of FA composition with temperature was reflected in the relative proportion of saturated FA (SAFA), monounsaturated FA (MUFA) and polyunsaturated FA (PUFA). Organism exposure to overheated water resulted in increased SAFA and MUFA content at the expense of PUFA. This effect can be promoted in phytoplankton with high light intensity and sunshine duration.

Fatty acid (FA) compositions were determined for the invader amphipod Dikerogammarus villosus collected from July to September 2002, in an overheated, high-conductivity dammed reservoir in north-eastern France. Predominant fatty acids were the polyunsaturated fatty acids (PUFA): eicosapentaenoic acid (EPA), linoleic acid (LA), arachidonic acid (ARA), linolenic acid (LNA) together with the monounsaturated fatty acid 18:1omega9 and the saturated fatty acid 16:0. FA markers indicated that available food was constituted of incompletely degraded phytodetritus and terrestrial inputs, as well as animal remains. PUFA contents depended on the diet and the capacity of animals to desaturate and elongate LNA and LA in long chain PUFA as EPA and ARA respectively. Based on their FA compositions, we showed that gammarids represent naturally-occurring freshwater sources of essential PUFA, and could play a fundamental role in pelagic-benthic coupling and energy recycling in the ecosystem. The complexity of the feeding strategies of D. villosus--detritivorous, omnivorous, carnivorous--makes this species efficient at exploiting different components of the available food and may be a key factor in its high invasive success.

International audience; Blooming of algae and more generally phytoplankton in water ponds or marine environments can lead to hyper eutrophication and lethal consequences on other organisms. The selective recognition of invading species is investigated by automatic recognition algorithms of optical and fluorescence imaging. On one hand, morphological characteristics of algae of microscopic imaging are treated. The image processing lead to the identification the genus of aquatic organisms and compared to a morphologic data base. On the other hand, fluorescence images allow an automatic recognition based on multispectral data that identify locally the ratio of different photosynthetic pigments and gives a unique finger print of algae. It is shown that the combination of both methods are useful in the recognition of aquatic organisms.

Valve activity was measured in the Mediterranean mussel Mytilus galloprovincialis in response to sublethal concentrations of four metals (Hg, Cu, Zn and Cd) and two phosphate industry effluents from the Atlantic coast of Morocco. Valve movements were monitored using a proximity inductive sensor which could display all activity figures from full closure to wide opening of the shell valves. In a 1 h exposure experiments, all metals induced a decrease in the time of normal opening and the appearance of sequences of stress behaviour, including enhanced valve adductions and complete closure at high concentrations. Mercury (tested from 5 to 75 microg Hg l(-1)) was the most toxic to the valve activity, with a threshold effective concentration at 10 microg Hg l(-1) and full valve closure occurring at 50 microg Hg l(-1). Copper (15-150 microg Cu l(-1)) showed a toxic effect starting at threshold concentration of 20 microg Cu l(-1) and induced full valve closure at 150 microg Cu l(-1). Zinc (100-500 microg Zn l(-1)) was effective in reducing the time of normal opening (threshold concentration at 100 microg Zn I(-1)) but no complete closure was recorded in any of the tested concentrations. For cadmium (1000-5000 microg Cd l(-1)), the valve activity was insensitive for exposures under 2000 microg Cd l(-1). Results for the testing of several samplings of the phosphate industry effluents (Safi and Jorf Lasfar) showed that their toxicity varied over the time. The effluent of the Jorf Lasfar plant (2-9.4%) was, however, more toxic than that of Safi (1-25%). In the light of these results, the sensitivity of the valve activity of Mytilus galloprovincialis to pollutants and its usefulness for in situ monitoring of coastal pollution in Morocco are discussed.

To assess the estrogenic potency of the treated domestic sewage effluent from a sewage treatment plant (STP) located in Lisbon (Chelas), 60 mirror carp (Cyprinus carpio) were exposed to different concentrations of the sewage effluent (0%, 25%, 50% and 100%) for two periods of 28 days in two different seasons (winter/spring). Vitellogenin induction in males was used as a biomarker of exposure to xenoestrogens. At the end of the experiment, blood samples were taken for vitellogenin analysis and the fish were sacrificed and dissected. Gonad samples were taken for histological evaluation of the sewage effects. The results showed an increase in vitellogenin induction in exposed fish, both males and females, depending on the different dilutions of the sewage effluent. In comparison with controls, the gonadosomatic index decreased significantly (P

Four species of aquatic mollusks, three bivalves: Anodonta cygnea, Unio pictorum and Dreissena polymorpha , and one gastropod: Viviparus viviparus were collected in a lowly polluted area and transferred to three monitoring sites, one upstream and two downstream of a chlorine bleached pulp and paper mill effluent. During the 28 days of the experiment, water, sediment and mollusks were sampled at regular intervals and analyzed for organo-halogenated residues using the sum parameters AOX and EOX. AOX concentrations in the water of the downstream sites were subjected to daily fluctuations due to the mill activity, while they remained stable in the sediments. The EOX concentrations in the mollusks exposed at the upstream site remained steady during the 28 days of exposure. Downstream, the EOX concentrations at both sites increased regularly in the four species of mollusks.

Field study allows assessment of long-term effects on fatty acid (FA) composition of organisms under chronic exposure to metals. One expected effect of copper is peroxidation of lipids and essentially polyunsaturated fatty acids (PUFA). FA analysis was established for the amphipod Dikerogammarus villosus subjected to different degrees of copper exposure (4-40 microg Cu L(-1)). A previous study in our team showed that this species regulates its body Cu concentration (106-135 mg Cu kg(-1) dry weight). Despite the high capacity of bioaccumulation, the absence of a correlation between copper concentration in D. villosus and water prevents its use as bioindicator of copper pollution. Both sexes from the most polluted site showed the lowest total FA content, but the highest PUFA percent, mainly of the long-chained variety (C20-C22). Mechanisms leading to the prevention of lipid peroxidation in this species were discussed (metallothioneins and intracellular granules) and proposed with support from literature data.

Freshwater mussels, Anodonta cygnea L., were collected in a lowly polluted area in north-eastern France, and exposed during 28 days at three sites up and downstream of a chlorine bleached pulp and paper mill effluent. Water, sediment and mussel samples were collected at regular intervals and analyzed for halogenated organic residues using the sum parameters AOX (Adsorbable Organic Halogen) and EOX (Extractable Organic Halogen). The survey of the water showed a chronic contamination by organic halogens of the water and the sediment downstream of the pulp and paper mill sewer. Mussels exposed upstream of the mill showed no significant variation of their EOX tissue concentration. In contrast, progressive accumulation of EOX occurred with the exposure time in mussels exposed downstream of the mill. No steady state of the EOX concentration was observed after four weeks of exposure.