We investigated the taxonomic composition of flagellate assemblages and taxon-specific bacterial grazing rates of heterotrophic and mixotrophic flagellates in the oligotrophic Lake Annecy (France). The comparison of bacterial grazing rates to bacterial production demonstrated a high transfer efficiency from the bacterial compartment up to flagellates. Per capita grazing rates ranged from 1.2x10(3) to 5.1x10(6) bacteria l(-1) h(-1) for heterotrophic flagellates, and from 4.8x10(6) to 6.8x10(7) bacteria l(-1) h(-1) for mixotrophic flagellates. The main bacterial grazers were Katablepharis within heterotrophic flagellates and Dinobryon within mixotrophic flagellates. Our results show that bacterial ingestion by a given flagellate taxon changed seasonally and could vary up to 30-fold. We also provide evidence that mixotrophic flagellates represent an important link in the flux of materials through planktonic food webs in Lake Annecy, suggesting that the introduction of mixotrophs within functional groups could improve our understanding of carbon flux pathways.

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We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotrophic flagellates, and ciliates from March to July 2002 in the surface waters (0-50 m) of Lake Bourget. The heterotrophic bacteria consisted mainly of "small" cocci, but filaments (>2 microm), commonly considered to be grazing-resistant forms under increased nanoflagellate grazing, were also detected. These elongated cells mainly belonged to the Cytophaga-Flavobacterium (CF) cluster, and were most abundant during spring and early summer, when mixotrophic or heterotrophic flagellates were the main bacterial predators. The CF group strongly dominated fluorescent in situ hybridization-detected cells from March to June, whereas clear changes were observed in early summer when Beta-proteobacteria and Alpha-proteobacteria increased concomitantly with maximal protist grazing pressures. The analysis of protist community structure revealed that the flagellates consisted mainly of cryptomonad forms. The dynamics of Cryptomonas sp. and Dinobryon sp. suggested the potential importance of mixotrophs as consumers of bacteria. This point was verified by an experimental approach based on fluorescent microbeads to assess the potential grazing impact of all protist taxa in the epilimnion. From the results, three distinct periods in the functioning of the epilimnetic microbial loop were identified. In early spring, mixotrophic and heterotrophic flagellates constituted the main bacterivores, and were regulated by the availability of their resources mainly during April (phase 1). Once the "clear water phase" was established, the predation pressure of metazooplankton represented a strong top-down force on all microbial compartments. During this period only mixotrophic flagellates occasionally exerted a significant bacterivory pressure (phase 2). Finally, the early summer was characterized by the highest protozoan grazing impact and by a rapid shift in the carbon pathway transfer, with a fast change-over of the main predators contribution, i.e., mixotrophic, heterotrophic flagellates and ciliates in bacterial mortality. The high abundance of ciliates during this period was consistent with the high densities of resources (heterotrophic nanoflagellates, algae, bacteria) in deep layers containing the most chlorophyll. Bacteria, as ciliates, responded clearly to increasing phytoplankton abundance, and although bacterial grazing impact could vary largely, bacterial abundance seemed to be primarily bottom-up regulated (phase 3).

[1] Barbel and gudgeon differ in their biology and ecology so that their bioturbation of streambed sediments may have specific effects on the patch dynamics of the sediment transport. Using experimental streams, we tested this idea by measuring the impact of a naturally occurring biomass gradient of each fish on the (1) transport of gravel and sand at base flow; (2) sediment surface characteristics; and (3) critical shear stress (t C ) causing incipient gravel and sand motion during simulated floods. Corresponding to their biology and ecology, the fish specifically modified base flow transport and surface of the sediments. The greatest t C reduction for gravel/sand caused through these base flow fish activities was $50%/$60% in the barbel and $35%/$60% in the gudgeon experiment. We integrate these results into a conceptual framework that outlines the contribution of benthic animals to the patch dynamics of the gravel and sand transport in real streams.

O2M3M5MPYR] as the cation and bis(trifluoromethanesulfonyl)imide [NTf 2 ], trifluoromethanesulfonate [TfO], dicyanamide [N(CN) 2 ], thiocyanate [SCN] or iodide as the anion have been synthesized, and their physicochemial properties have been studied. Thermal properties, solubilities in water and water contents, UV-vis spectra, densities, refractive indices, electrochemical windows, and toxicities on Vibrio fischeri have been measured. These ionic liquids, most of which are liquid at room temperature, exhibit high refractive indices and increased hydrophobicity. Despite high toxicity values toward V. fischeri, ionic liquids containing a dialkylpyridinium or trialkylpyridinium cation with an octyl chain represent good alternatives to extracting solvents. † Part of the "Josef M. G. Barthel Festschrift".