The habitats of 356 phytocoenoses dominated by 15 species of aquatic plants were investigated. Among the properties of water, Na+, pH, total Fe, Ca2+, NO3−, SO42−, hardness and COD-KMnO4 were the most important in differentiating the habitats of the phytocoenoses studied. Considerable physicochemical differences were found between the waters of the phytocoenoses of Ranunculus circinatus (hard waters rich in Na+), Nuphar pumila (soft waters with high levels of total Fe), Elodea canadensis, Ceratophyllum demersum (alkaline waters) and Stratiotes aloides (waters containing high concentrations of Ca2+ and SO42−). The substrate properties that best differentiated the habitats compared were PO43−, hydration, organic matter content, total N, dissolved SiO2, Ca2+, Na+ and pH. Patches of R. circinatus inhabited substrates containing the highest levels of PO43−. Those of S. aloides were associated with substrates poor in PO43−. Patches of C. demersum were confined to substrates rich in total N. Phytocoenoses of R. circinatus were associated with large lakes, whereas those of N. pumila were restricted mostly to smaller lakes. The deepest parts of lakes were inhabited by Potamogeton lucens. Phytocoenoses of S. aloides occurred mostly in shallow waters, on thick sediments. The investigated phytocoenoses also represent different stages of succession. The phytocoenoses of Potamogeton perfoliatus, R. circinatus, Myriophyllum spicatum and Polygonum amphibium, which develop on mineral substrates, initiate the process of succession, whereas those of Myriophyllum verticillatum, Nymphaea candida, Nymphaea alba, N. pumila and S. aloides, which inhabit highly hydrated organic substrates, are characteristic of the late stages of succession.

Podonomus Philippi was recently found in Brazilian inselbergs. In this study, we used sequences from the barcode region of cytochrome c oxidase I (COI) to assess Podonomus molecular diversity from mountains in Southeastern Brazil. Our results revealed the adult female and the larvae of Podonomus pepinellii Roque and Trivinho-Strixino, 2004 and extended the known geographical distribution of the species. Moreover, we found high molecular divergence in two populations located in the Serra da Mantiqueira and Serra do Espinhaço mountain range when compared with the only species recorded to Brazil, indicating the possibility of two more species to be described.

Difficulties to simply transfer trophic cascade theory from temperate to tropical lakes are now well recognized. Many mechanisms trying to explain top-down divergences between these systems have been proposed, such as lack of key species of herbivorous zooplankton, absence of seasonality in fish reproduction, cyanobacteria development, or differences in fish foraging behaviour. Very few studies have considered bottom-up mechanisms, in particular differences in nutrient recycling and nutrient limitation between the two types of ecosystems. According to the ecological stoichiometry theory, fish-induced alterations of food-web structure could modify the efficiency of consumer-driven nutrient recycling by changing the relative biomass contribution of species in food webs. Consequently, by mostly considering top-down processes, one could underestimate consequences on nutrient availability for phytoplankton growth. In this paper, we compared the results of two mesocosm experiments carried out in temperate and tropical areas, each manipulating food-web structure via the presence or absence of fish. We found trophic cascades in both experiments, but differences between fishless and fish treatments were greater in temperate than in tropical systems. In the tropical experiment, the observed effects could not be supported by classical zooplankton community alteration or by cyanobacteria prevalence. Our results suggest a key contribution of fish nitrogen-excretion to phytoplankton growth in mostly nitrogen-limited tropical systems. Differences in stoichiometric response to food-web structure alteration between temperate and tropical lakes could thus represent a major difference between the two systems. Our study stresses the need for further studies that would allow robust generalization on the functioning of freshwater temperate and tropical ecosystems.

Dans cette note, nous décrivons une méthode simple, permettant l'ultracentrifugation de particules virales planctoniques et leur observation en microscopie électronique à transmission. Une description de différents morphotypes de particules assimilables à des virus est faite à partir d'échantillons prélevés dans la couche euphotique d'un lac eutrophe (Aydat), au cours des périodes printanière et estivale. Ces particules présentent chacune une capside icosaédrique régulière à 6 faces et une queue, dont les dimensions sont similaires à celles des phages décrits en milieu marin. La diversité des formes et le nombre de virions (10 fois supérieur à celui des bactéries), permettent d'émettre l'hypothèse selon laquelle les virus interviennent de façon significative dans le contrôle des abondances des communautés bactériennes en milieu lacustre.

Phytoplankton was sampled over 10 months at five stations along the north-eastern coast of Lake Tanganyika. The biomass is composed chiefly of diatoms together with blue-green algae and, occasionally, green algae and Euglenophytes. Seasonal changes in phytoplankton composition and densities are discussed in relation with abiotic factors.

Le but de cette étude est de mieux connaître la qualité de l'eau et la macrofaune benthique des cours d'eau marocains duMoyen-Atlas. L'Oued Tizguit a été choisi pour son accessibilité et la variété de son environnement. Onze stations ont été suiviesen mesurant 8 paramètres physico-chimiques et en faisant l'inventaire faunistique pendant un cycle hydrologique.Ce travail montre que la qualité de l'eau évolue dans le temps selon un gradient amont-aval.Des prélèvements qualitatifs ont permis de dénombrer 167 taxons appartenant à différents groupes où les Coléoptères sontmajoritaires. La distribution de cette macrofaune semble déterminée par la variation longitudinale des différents paramètres dumilieu, et sa composition doit son originalité, en partie, à la qualité de l'eau du milieu.

Rainbow trout is one of the most popular introduced game species around the world. Similar patterns of use for lake and inlet streams have been described for both native and introduced populations. However, for many introduced rainbow trout populations, there is a lack of information about how and when those habitats have been used. Here, we hypothesized that the majority of adult and sexually mature individuals inhabit inlet streams during the reproductive period most likely to spawn whereas juvenile trout occupy these same streams as nursery areas most of the year before emigrating to the lake. We studied rainbow trout age distribution and sexual maturity in a lake and its main inlet streams in southern Chile. We found that stream-dwelling individuals inhabited inlet streams up to age 2+ whereas lake-dwelling trout were older (most of them from ages 4+ to 6+). During the reproductive period (May to September) older and sexually mature individuals were in both habitats probably indicating movement to upstream locations to spawn. Rainbow trout of the same ages were larger in the lake than in streams, which may imply better growth in the lenthic environment. Our study offers further evidence of the highly adaptable nature of rainbow trout. Future regulations should consider rainbow trout populations in lakes and streams separately because trout life histories suggest that both environments are important to different ontogenic stages. This study provides key information that may be useful in the management of ad-fluvial populations of rainbow trout in Patagonia.

Des investigations malacologiques ont été réalisées en 1994-1995 le long de deux secteurs de rivière pour dénombrer les gîtes du mollusque Lymnaea truncatula et déterminer leurs caractéristiques. Les deux secteurs étudiés concernent a) la Creuse sur 10 km, à côté d'Argenton-sur-Creuse (Indre) et b) la Vienne sur 25 km, entre Saint-Victurnien (Haute-Vienne) et Etagnac (Charente). Le mollusque est présent dans 27 stations sur la Creuse mais on note de grandes variations dans l'abondance de la limnée : 6 gîtes avec moins de 10 L. truncatula en juillet, 9 avec 11 à 20 limnées, 6 avec 21 à 50 mollusques, et 6 avec plus de 51 individus. La longueur des gîtes ne dépasse pas 5 m dans 15 cas, 10 m dans 6 cas, 15 m dans 4 cas et 35 m dans les 2 autres stations. Neuf gîtes à L. truncatula ont été retrouvés sur les 25 km de la Vienne. Un habitat est fort de 101 limnées tandis que les autres ont de faibles effectifs avec moins de 50 limnées par gîte. Le gîte s'étend sur 5 mètres de rive dans huit cas et sur 30 m dans l'autre cas. De cette étude, il ressort que ces berges de rivière ne constituent pas un milieu favorable pour le développement de l'espèce.

Ce travail est une contribution à la connaissance faunistique et écologique des oligochètes de deux cours d'eau du Midi de la France : l'Argens et un de ses affluents, l'Eau Salée. Nous présentons une première diagnose d'un Tubificidae indéterminé du genre Peloscolex et nous donnons un complément à la description d'Epirodrilus pygmaeus Hrabe qui est signalé ici pour la première fois en France. Nous abordons également quelques points intéressants concernant la répartition géographique de certaines espèces : Chaetogaster setosus Svetlov, Tubifex tubifex blanchardi Vejdovsky, Epirodrilus pygmaeus Hrabe et Lumbri-cillus kaloensis Nielsen et Christensen.

Les périodes de maturité observées pour les oligochètes de ces cours d'eau sont récapitulées dans un tableau. A partir de nos observations et des données de la littérature nous précisons les préférendums écologiques de chacune des principales espèces avant de conclure sur la répartition longitudinale des oligochètes dans ces deux cours d'eau.

Considerable spatial and temporal variability was detected in the environmental conditions in 30 coldwater springs in southernOntario, Canada. Using standard pyramidal emergence traps, a total of 86 insect species was recorded from these springs (notincluding the Chironomidae). These represented nine taxonomic groups, among which the Limoniidae (Diptera) was the mostdiverse with 38 species. Fifty-five per cent of all species recorded had a low frequency (found at three or fewer sites), and onlyfor very few of these rare species were more than 10 individuals m-2 collected. Interannual differences were also apparent.Continuous sampling over time showed that emergence records from a single year, on average, contained only around 50% ofthe total number of species obtained during the entire study. Species-environment relationships analyzed by CanonicalCorrespondence Analysis indicated that temperature and discharge correlated most strongly with insect community similarityamong spring sites. The prospects for developing regional typologies of coldwater springs, based on their environmental conditions,and the implications of species loss to the continuity of function of coldwater spring ecosystems are discussed.

The role of heterotrophic biofilm of water–sediment interface in detoxification processes was tested in abiotic and biotic conditions under laboratory conditions. Three toxicants, a herbicide (Diuron), a fungicide (Dimethomorph) and an insecticide (Chlorpyrifos-ethyl) have been tested in water percolating into columns reproducing hyporheic sediment. The detoxification processes were tested by comparing the water quality after 18 days of percolation with and without heterotrophic biofilm. Tested concentrations were 30 μg.L−1 of Diuron diluted in 0.1% dimethyl sulfoxide (DMSO), 2 μg.L−1 of Dimethomorph and 0.1 μg.L−1 of Chlorpyrifos-ethyl. To characterise the detoxification efficiency of the system, we performed  genotoxicity bioassays in amphibian larvae and rotifers and measured the respiration and denitrification of sediments. Although the presence of biofilm increased the production of N-(3,4 dichlorophenyl)-N-(methyl)-urea, a metabolite of diuron, the toxicity did not decrease irrespective of the bioassay. In the presence of biofilm, Dimethomorph concentrations decreased compared with abiotic conditions, from 2 μg.L−1 to 0.4 μg.L−1 after 18 days of percolation. For both Dimethomorph and Chlorpyrifos-ethyl additions, assessment of detoxification level by the biofilm depended on the test used: detoxification effect was found with amphibian larvae bioassay and no detoxification was observed with the rotifer test. Heterotrophic biofilm exerts a major influence in the biochemical transformation of contaminants such as pesticides, suggesting that the interface between running water and sediment plays a role in self-purification of stream reaches.

The population dynamics and life cycle of two mollusc species Pisidium amnicum and Valvata piscinalis of the Saône river werestudied for nine years. The newborn of the former species appeared in April each year. The latter species produced two cohorts peryear until 2003. Spawning in spring led to the birth of the early cohort, which generally appeared in May, while spawning in thesummer led to the birth of the late cohort, which appeared from July to November. The increase of the mean annual temperature by1.9°C from 1998 to 2000 was followed by an increase in the density of mollusc populations, possibly triggering or amplifying interand intra specific competition for food. However, the 2003 heatwave was responsible for the sudden decline of the P. amnicumpopulation, then the more progressive decline of that of V. piscinalis after having strongly modified its demographic structure andits life cycle. In 2004 and 2005 V. piscinalis only produced one cohort per year. The observations carried out strongly suggest thatthe insufficiency of available resources was one of the possible causes of their failure to recover in 2004 and 2005. The increase ofglobal warming predicted by different models could result in the gradual disappearance of P. amnicum from the potamon and ofV. piscinalis from the freshwater systems most directly exposed to climatic warming, such as the Saône River.

This paper focuses on relationships between the North Atlantic Oscillation Index (NAO) and the ice conditions in coastal lakes (Jamno, Bukowo, Gardno and Lebsko) of the southern Baltic Sea. The data on ice conditions included : date of first ice appearance (F), date of last ice disappearance (D), number of days with ice (N), length of the ice season (in days ; S) and maximum ice thickness (H) during the given winter. The period examined covers the winters from 1960/61 to 1999/2000. The monthly values of the NAO index for the same period were applied in accordance with Jones et al. (1997). Correlation and regression analysis methods were applied to determine and study the relationships between NAO (independent variable) and the parameters of ice conditions (dependent variables). The strongest relationships, with a linear correlation coefficient exceeding - 0.80, were obtained for the date of the last ice disappearance (D) in Lebsko Lake (- 0.853) and Gardno Lake (- 0.828) for the January March period. In contrast, the relationships between the NAO index and the date of first ice appearance (F) are much weaker. They are statistically significant only in November and early winter (Nov.-Dec., Nov.-Jan.). The correlation coefficients in the coastal lakes of the Southern Baltic Sea coasts generally increase eastwards, a phenomenon related to the severity of winters and to the increasing continuity of ice phenomena during a given winter in this direction.

Les proliférations de macrophytes atteignent désormais les eaux courantes et entraînent de nombreuses nuisances. La compréhension de ce phénomène nécessite une étude approfondie des peuplements végétaux en place et des paramètres d'environnement qui les conditionnent, afin de déterminer les phytocénoses de référence et leurs séquences de dégradation. Lors de cette étude, vingt et un cours d'eau, situés en tête de bassin versant et représentatifs de la diversité géologique de la Lorraine, ont été prospectés. Le choix des stations d'étude a été réalisé en fonction d'un découpage abiotique, définissant des zones de cours d'eau homogènes au niveau de la géologie, la pente et la largeur. La pertinence de l'utilisation de la géologie (classes de perméabilité) comme premier critère hiérarchique de classification des cours d'eau est confirmée par les résultats de cette étude. Les analyses chimiques et les relevés morphométriques effectués sur chaque station d'étude ont conduit à individualiser quatre grands types de cours d'eau (sur granites, sur grès, sur calcaires et sur marnes), dont la végétation aquatique a été inventoriée. Des successions végétales typiques en fonction de la position amont-aval ont été observées. Les notions de milieux naturellement fragiles et d'espèces « à risque de prolifération » ont été affinées. Cette étude constitue la base d'une typologie des cours d'eau par la végétation aquatique.

Ecological requirements of ostracods in two limnocrene springs (Usta and Çetin Bey) were investigated between January 2000and July 2002 in Bolu, Turkey. Ten taxa (Candona neglecta, Darwinula stevensoni, Eucypris virens, Eucypris sp., Heterocyprisincongruens, Herpetocypris sp., Ilyocypris bradyi, Potamocypris sp., Scottia pseudobrowniana, Tonnacypris lutaria) werefound. Canonical correspondence analysis (CCA) showed that species with wide cosmopolitan distribution could tolerate highlevels of changes in environmental variables. CCA explained about 80 % and 77 % of the relationships between species andenvironmental variables in Usta and Çetin Bey springs, respectively. Electrical conductivity and dissolved oxygen were the twomost influential factors on species occurrence in each spring. According to Spearman correlation analysis, there were no significantrelationships between the numbers of species and environmental variables in both springs. When dissolved oxygen showedsignificant negative correlations to electrical conductivity, water and air temperature in Usta spring, such correlation wasonly negatively significant (P <0.05, r = -0.46) between electrical conductivity and dissolved oxygen in Çetin Bey spring.Clustering analysis (UPGMA) of presence/absence data divided species into four main groups. Results may suggest that anthropogenicactivities were responsible for decreasing water quality of these springs and reducing species richness. Although increasingincentives for conservation of natural springs were proposed, Çetin Bey spring and especially Usta spring are now highlydegraded.

Toxic cyanobacteria are common in Portuguese freshwaters and are a cause of concern, given that exposure to subacutelevels of cyanobacterial toxins through drinking and recreational water might have deleterious effects on human health.Since 1996 several laboratories have been involved in the screening of cyanotoxins in different freshwater bodies, some on aregularly basis but most on a sporadically basis. Here we present data on the phytoplankton communities and on microcystinsproduction occurring in six freshwater reservoirs located in a dry region of south Portugal, from May to December 2005 andApril to July 2006. Most of the reservoirs experienced cyanobacterial blooms of various intensities, following noticeable shiftsin phytoplankton composition towards cyanobacterial dominance. The seasonal dominance of cyanobacteria during warmerperiods was not a fi xed pattern since considerable amounts of cyanobacteria were also recorded during winter months in somereservoirs. Microcystins were detected in 23% of the 53 samples tested and some of them had concentrations higher than theWHO guideline of 1μg L-1 of microcystins, but their amounts not always reflected the encountered cyanobacteria biomass.Although Microcystis aeruginosa seems to be the major species responsible for microcystins production, other potentiallytoxigenic bloom-forming species were also found. These results reflect the irregular and unpredictable nature of cyanobacterialblooms in what respects to their occurrence, their composition, their intensity and persistency, as well as to their overall toxicity,strengthening the need of a systematic survey of freshwater resources for the correct risk assessment of cyanobacteria andassociated toxins in natural environments.

Cladocerans are used in a wide range of applications (aquatic toxicology, experimental hydrobiology, and aquaculture). Although known to be successfully cultivated with microalgal food sources, cladoceran demographic parameters tend to be different, depending on the kind of cladoceran and concentration of food supplied. For most species, finding precise instructions on culture conditions and expected outcomes is difficult. The aim of this study was to determine the most favorable feeding conditions for the development of three cladoceran species frequently used as test organisms in aquatic toxicology. For this purpose, Ceriodaphnia dubia, Daphnia pulex, and Simocephalus mixtus were fed three concentrations (6, 12, and 18 mg L-1 dry weight) of the green microalgae Ankistrodesmus convolutus, Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum), and Scenedesmus incrassatulus. Reproduction and survival were evaluated during the entire life cycle. For C. dubia, the P. subcapitata and S. incrassatulus diets produced the best reproductive results. For D. pulex, the best overall results were obtained with S. incrassatulus at 6 mg L-1 and results with P. subcapitata were similar at all concentrations. For S. mixtus fed P. subcapitata, results were similar at all concentrations. With S. incrassatulus, a decrease in longevity and an increase in fecundity occurred as the amount of food increased; the best reproductive response was achieved with the highest (18 mg L-1) concentration. The lowest reproduction and survival in the three cladocerans were recorded with A. convolutus. For the cladoceran species tested, the same microalga produced different reproductive and survival results, depending on the concentration; some of the tested foods did not support adequate cladoceran development, because they were nutritionally deficient, despite the similar conditions used for their production. Feeding and culture conditions here described could be useful for a controlled propagation of these cladocerans.

The objectives of this study were to evaluate fish guild compositions and national river health using a multi-metric model of the Korean index of biological integrity using fishes (K-IBIF) in four major Korean watersheds along with water chemistry and habitat quality. Tolerant and omnivore fish species dominated all the watersheds, and the proportions of tolerance guilds and trophic guilds reflected water chemistry and habitat quality. The number of sensitive species and insectivore species had negative correlations (r < −0.42, P < 0.01) with chemical water quality (biological oxygen demand (BOD)), while tolerant species and omnivore species had positive correlation (r > 0.27, P < 0.05) with BOD values. Physical habit conditions, based on qualitative habitat evaluation index (QHEI) model, indicated a “good” condition (mean = 68.9; range = 45–105) in three watersheds, except for the Yeongsan River watershed. Values of QHEI were significantly correlated (R2 > 0.4, P < 0.01) with nitrogen and phosphorus levels in all watersheds, suggesting that habitat degradation is associated with eutrophication. Model values of K-IBIF in the watersheds averaged 18.2, indicating a “fair” condition, and about 37% of all observations in K-IBIF model values were judged as a “poor” health condition, indicating severe health impairment. Overall, our data suggest that degradation of the river health was due to a combined effect of chemical pollution and physical habitat modifications. This research provides valuable information on Korean river conservation and restoration in the future.

As part of a wetland conservation programme for the Southern shore of lake Neuchatel (Western Switzerland), an experiment was started in 1993 to slow down the terrestrialization of the wetland. Sediments were removed in a reed-belt adjacent to an existing pond, at three different depths (0.20, 0.30 and 0.40 m), thus creating a new shallow pond. The colonisation by aquatic vegetation and invertebrates was monitored during three years (1994–1996) to evaluate the effect of the creation of a new pond on the chironomid diversity and abundance through time. Chironomids (78 taxa) were among the most diverse group colonising this fringing wetland. Significant differences in abundance were found between the reed-belt and the pond habitats (existing and recently created ponds). As expected, the latter was more productive, especially during the first two years of colonization. However, the chironomid diversity in the newly created pond, measured by the rarefied richness, was intermediate between the reed-belt (low diversity) and the pre-existing pond. Ordination of the sites on the basis of their chironomid assemblages confirmed this trend. The depth at which the sediment was scrapped off, had no major influence upon the chironomid assemblages. Finally, within the three years after creation of open water habitats, the production of chironomids and consequently their availability for dabbling ducks and wetland birds, were enhanced. However, this time was not enough for the chironomid community to reach the diversity of the pre-existing pond, to which it is connected. The creation of shallow ponds seemed to be crucial to slow down terrestrialization processes in this lacustrine wetland and to have only slight effects on the chironomid communities.

La comparaison de ruisseaux temporaires et permanents a été réalisée afin de déterminer leurs affinités. On a noté une stabilité des facteurs physiques et chimiques dans les ruisseaux permanents et pendant la phase lotique des ruisseaux temporaires; la phase stagnante des ruisseaux temporaires se révèle très instable. La comparaison des facteurs biotiques révèle l'affinité des ruisseaux permanents calmes et des ruisseaux temporaires. Les ruisseaux permanents à cours rapide et les ruisseaux temporaires sont peu affines. Quelques populations spécifiques peuvent survivre à la période sèche des ruisseaux temporaires, seulement lorsque la nappe phréatique est présente en profondeur.