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The composition, distribution and extracellular enzyme activities of bacteria attached to small (2-50 microm in size) transparent exopolymer and Coomassie-stained proteinaceous particles (TEP and CSP) were examined in two lakes of different trophic status located in the Massif Central of France. TEP concentrations (10(4)-10(6) particle per L) were significantly higher in the more productive lake and were significantly related to chlorophyll a concentrations. The majority of TEP and CSP were colonized by bacteria that constituted 2.6% and 7.4% of the total 4',6-diamidino-2-phenylindole-stained bacteria in lakes Pavin and Aydat, respectively. In both lakes, the composition of particle-associated bacteria was different from that of free-living bacteria, the Betaproteobacteria and Bacteroidetes (i.e. former Cytophaga-Flavobacteria group) being the dominant groups on particles. We also found that 2-5 microm TEP were more colonized than 2-5 microm CSP in the two lakes, and that TEP colonization was higher in the less productive lake. Measurements of Leucine aminopeptidase and alpha-glucosidase activities in fractionated lake water (0.2-1.2, 1.2-5 and >5 microm fractions) indicated that proteolytic activity was always higher and that particle-associated bacteria have higher enzymatic activities than free-living bacteria. The glycolytic activities in the 1.2-5 and >5 microm fractions were related to the abundance of TEP. We conclude that small freshwater detrital organic particles constitute microhabitats with high bacterial activities in pelagic environments and, undoubtedly, present significant ecological implications for the prokaryotic community structure and function in aquatic ecosystems.

International audience; The incorporation of [3H-methyl] thymidine (3H-TdR) by Eubacteria, bacterial groups (alpha- and beta-Proteobacteria, Cytophaga-Flavobacter), and Archaea was measured according to temperature (7 and 17 degrees C) and nutrient levels (nitrogen, phosphorus, and carbon) in a lacustrine system (Sep, France). Short-term incubation was performed using a combination of microautoradiography and fluorescent in situ hybridization. Irrespective of the temperatures and nutrients studied, all the major phylogenetic bacterial groups assimilated 3H-TdR, and in most of the treatments studied, the proportion of beta-Proteobacteria taking up 3H-TdR was higher than those in the other bacterial groups. The proportion of Bacteria and different bacterial groups studied incorporating 3H-TdR were significantly increased, approximately 1.5-fold, by temperature except for alpha-Proteobacteria (7.6-fold). The nutrient effect was not the same for the different bacterial groups according to the temperatures studied. The proportions of alpha-Proteobacteria (at both temperatures) and Cytophaga-Flavobacter (at 7 degrees C) taking up 3H-TdR were significantly decreased and increased by adding N and P, respectively. Also, adding N, P, and C increased and decreased the percentage of beta-Proteobacteria incorporating 3H-TdR at 7 and 17 degrees C, respectively. The archaeal community showed a similar proportion of active cells (i.e., 3H-TdR) to the bacterial community, and uptake of 3H-TdR by Archaea was significantly increased (P < 0.05) by both temperature and nutrients. Thus, the assimilation of 3H-TdR by bacterial groups and Archaea in lacustrine system is significantly controlled by both temperature and nutrients.

The specific growth rates of ciliates were measured in diffusion chambers after the first flooding of a reservoir. The abundance of nanoplankton and the high concentrations of dissolved organic matter could explain why the growth rate, whose average value was 0.07 ± 0.06 h -1 , was higher than that recorded in other lakes of similar trophic status. The abundance of ciliates was strongly controlled by Daphnia longispina and Asplanchna priodonta.

(2002). Functioning of a lacustrine ecosystem in a newly flooded reservoir (Sep, Puy de Dome, France): modelling of carbon flux between the different food web compartments. SIL Proceedings, 1922-2010: Vol. 28, No. 3, pp. 1253-1257.

Temporal changes in the plankton community and trophic relations between the metazooplankton and its potential prey (bacteria, flagellates, ciliates and algae) were studied following the flooding of a new reservoir (Sep, France). The high dissolved organic matter (DOM) concentrations favoured the development of heterotrophic and mixotrophic organisms, which dominated the unicellular plankton after flooding. The proportion of strictly autotrophic organisms increased with time, reaching 67 % of the biomass of protistan plankton at the end of the study. A small-sized chrysomonade (2-5 μm) accounted for 53 % of the abundance of the heterotrophic nanoflagellates (HNF) throughout the study. The Chrysophyceae, Chrysidalis sp. accounted for 76 % of the mean relative abundance of all pigmented flagellates combined. Some mixotrophic species such as Dinobryon cylindricum and Cryptomonas ovata mainly occurred at the start of the study. The prostomatid ciliate Urotricha furcata, which dominated in terms of numbers immediately after flooding, was later replaced by mixotrophic species, an oligotrichid Pelagohalteria viridis then a peritrichid, Vorticella sp. The rotifers Polyarthra sp., Synchaeta sp. and Hexarthra mira were the first metazooplankton organisms to colonise the pelagic environment. They were replaced in the 3 rd year by Cladocera (Daphnia longispina and Ceriodaphnia quadrangula) and Copepoda, firstly calanoids (Eudiaptomus gracilis) and then cyclopoids (Cyclops vicinus and Acanthocyclops robustus). This study emphasizes the importance of the organisms of the microbial food web in the nutrition of the metazooplankton in the period following the flooding of a newly impounded reservoir.

The annual distribution of potential glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities was studied in the oligo-mesotrophic Lake Pavin (France, Massif Central). The validity of these enzymatic activies as an index of N-assimilation in field studies was tested by a comparison with the coupling of distributions of inorganic nitrogen uptake rate based on 14 C incorporation into proteins together with several abiotic and biotic parameters. The potential GS and GDH activities recorded during the annual phytoplankton succession were in the same order of magnitude as those reported from the very scanty literature on this subject. Moreover, specific potential GS and GDH activities were significantly correlated with the external NO 3 - -N concentration suggesting that these enzymatic activities reflected nitrate utilization by algae. Specific activities of GDH were about 2.5 fold higher than GS specific activities suggesting that the GDH pathway may play a leading part in inorganic nitrogen assimilation in the oligo-mesotrophic Lake Pavin. However, N-assimilation rates based on the enzymatic approach were lower than those obtained through indirect isotopic determination of N-uptake rates. The reasons for such a discrepancy are discussed.

International audience; The spatial distribution of bacterial abundance and production were measured every 4 h in a recently flooded oligo-mesotrophic reservoir (the Sep Reservoir, Puy-De-Dôme, France), in relation to concentrations of dissolved carbohydrates and combined amino acids. The concentration of dissolved organic matter (DOM) components in the recently flooded Sep Reservoir were higher than those measured in other lakes of similar trophic status. Short-term variations in the bacterial production in this new reservoir appeared cyclical and endogenous to bacterial communities. These results highlight the need for the evaluation of diel changes in bacterial production, if estimation of the daily production rate of bacteria is to be done accurately for a reliable model of carbon flow through bacterioplankton and ultimately through aquatic microbial food webs. Bacterial growth, measured over time and space, did not appear exclusively governed by DOM components from phytoplankton primary production.

International audience; Dialysis bags were used to examine the impact of predation and viral lysis on prokaryotic community composition (PCC) over a 5-day experiment in the oligomesotrophic Lake Pavin (France). The impact of the different predator communities (protists and metazoans) of prokaryotes was estimated by water fractionation (

Temporal changes in the bacterial community composition (BCC) and the impact of resources and predation on this community composition have been studied in the euphotic zone of the Sep reservoir (France), using terminal-restriction fragment length polymorphism (T-RFLP) and fluorescent in situ hybridization (FISH) for Eubacteria (EUB338) and eubacterial subgroups. Net growth and grazing rates of the various subgroups were computed from experiments conducted in dialysis bags in the presence or absence of predators. There was a significant difference between the grazing rates of different bacterial groups and subclasses, the alpha-proteobacteria (ALF1b) were subjected to the highest grazing rate (max. 1.76 d -1 ). In contrast, the beta-proteobacteria (BET42a) seemed to be little consumed by bacterivorous organisms, and predation led to large variations in the grazing rates of Cytophaga-Flavobacterium (CF319a). The different composition of bacterial con- sumers (Dinobryon sp. and Cladocera) during the study could explain the observed differences in grazing impact. The mean net growth rates of total bacteria, EUB338, BET42a ALF1b, and CF319a in dialysis bags without predators were 0.21, 0.69, 0.45, 0.50 and 0.84 d -1 , respectively. Various statisti- cal analyses indicated that the BCC could depend on the organic matter excreted by the phyto- plankton. There were also positive correlations not only between net growth and/or net production of ALF1b and CF319a with the primary production and biomass of the main phytoplankton groups, but also between phytoplankton biomass, primary production (PP) and some operational taxonomic units (OTUs). Among the physical variables, input and output of water in the reservoir seem to play a role in determining the BCC in this ecosystem. The results suggest that the BCC depends on the combined impact of dominant substrate sources and selective predation by bacterial consumers.

The study examines the relationship between floodplain aquatic macroinvertebrates and sector-scale parameters such as geomorphology and history of regulation. The assemblages of six groups of invertebrates (Molluscs, Crustaceans, Ephemeroptera, Odonata, Trichoptera, and Coleoptera) were compared in various types of former channels from two contrasting but adjacent floodplain sectors: (1) the Jons sector of the Rhǒne River where successive meandering and braiding phases has left diversified fluvial forms in the landscape but where the main river is now embanked, and (2) the unregulated Ain River sector where the river is still actively meandering, although this process is being slowed by incision. The results demonstrate little difference in faunal composition between the two sectors but a significant difference in faunal structure. In the Rhǒne floodplain, there was a clear distinction between the faunal assemblages together with a high taxa richness at the scale of the sector (dominance of the beta diversity). In the Ain floodplain, the faunal assemblages were overlapping and the taxa richness was high at the sample scale (alpha diversity). Sector-scale spatial patterns of the faunal assemblages along former channels were also distinct: between-channel heterogeneity dominated in the Rhǒne, whereas within-channel heterogeneity dominated on the Ain. These results stress the influence of geomorphological and historical determinants on the floodplain communities and, conversely, the relevance of macroinvertebrate assemblages for the assessment, at the landscape scale, of aquatic systems within the floodplains.

From February to August 1996, the following parameters were determined in surface water samples from an oligotrophic reservoir: concentrations of dissolved combined amino acids (DCAA), monosaccharides (DFCHO) and polysaccharides (DCCHO); activities of glycolytic and proteolytic enzymes associated with three size fractions (0-0.2 μm, 0.2-2 μm, and 2-100 μm); densities and biomass of free-living and attached bacteria, nanoflagellates, and metazoan zooplankton. The mean concentrations of DCAA, DFCHO and DCCHO were 2.7, 0.5 and 1.4 mg C l-1 respectively. Both βGlcA and αGlcA showed a high substrate affinity. The enzyme activities associated with all size fractions fluctuated throughout the year. Highest activities were generally associated with the 2-100 μm fraction; the mean percentages of leucine-aminopeptidase (LeuA), β-glucosidase (βGlcA), α-glucosidase (αGlcA) and β-N-acetylglucosaminidase (βGlcNAcA) activities were 58%, 62%, 76%, and 59%, respectively. Activities of αGlcA and βGlcNAcA in the 0.2-2 μm fraction were correlated with the abundance of free-living picobacteria (bacteria

This paper deals with the results of an extensive sampling of eight former channels of the Rhǒne and eight of its tributary, the Ain River, France, designed to assess the value of molluscs as ‚describers’ of ecosystem dynamics. The sampling was stratified on the distribution of aquatic macrophytes. The distribution of molluscs species is shown to provide information on the rate of eutrophication, the groundwater supply and the succession of the abandonned river channels toward semi-aquatic and terrestrial conditions. Molluscs, together with other macroinvertebrates, not only describe the present stage of these ecosystems but also provide some predictive information on their successional pattern for assistance in the management of the alluvial plain.

The hydrological analysis of one of the old meanders of the french upper Rhone, called the ‘Lone des Pecheurs’, is carried out from September 1976 to November 1977.

Le calcium s'accumule dans les tissues de Ferrissia wautieri sous forme de spherules de calcaire intracellulaires. Notre travail comporte une etude descriptive de ces cellules en microscopie optique et electronique, et une etude mineralogique abordee par des techniques de coloration, de dissolution, de polarisation de la lumiere et de diffraction electronique. Les resultats obtenus montrent que les spherules, par leur aspect, leur nombre, leur volume et leur etat de cristallisation, presentent des caracteres differents selon la saison, ce qui permet d'etablir une relation entre l'etat des nodules calcaires et les variations du metabolisme des individus.

Wautier Jacques, Pavans de Ceccatty M., Richardot M., Buisson B., Hernandez M.-L. Les étapes de la croissance chez Gundlachia sp.(Mollusque, Ancylidae). In: Bulletin mensuel de la Société linnéenne de Lyon, 31ᵉ année, n°3, mars 1962. pp. 70-73.

Wautier Jacques, Pavans de Ceccatty M., Hernandez M.-L., Richardot M., Buisson B. Histo-physiologie des corrélations neuro-hormonales lors du cycle sexuel de Gundlachia. In: Bulletin mensuel de la Société linnéenne de Lyon, 31ᵉ année, n°3, mars 1962. pp. 84-92.

Wautier Jacques, Richardot M. Croissance à température constante de l'ancyloïde de Gundlachia wautieri (Mollusque basommatophore). In: Bulletin mensuel de la Société linnéenne de Lyon, 35ᵉ année, n°10, décembre 1966. pp. 463-467.

Les elements morphologiques apportes par la microscopie electronique montrent que le muscle du bulbe buccal de Ferrissia wautieri differe du muscle strie squelettique par plusieurs caracteres mais presente avec celui-ci des analogies structurales qui peuvent conduire a considerer le type de fibre musculaire etudie comme une structure intermediaire entre la musculature lisse et la musculature striee.

Wautier Jacques, Pavans de Ceccatty M., Richardot M., Buisson B., Hernandez M.-L. Notes sur les complexes neuro-endocriniens de Gundlachia sp. (Mollusque Ancylidae). In: Bulletin mensuel de la Société linnéenne de Lyon, 30ᵉ année, n°4, avril 1961. pp. 79-87.