Bacterivory of a mudflat nematode community under different 1 environmental conditions 2

10 The fate of the benthic bacterial biomass is a topic of major importance in understanding 11 how soft-bottom environments function. Because of their high abundance, production and 12 nutritional value, benthic bacteria may constitute an important food resource for benthic 13 fauna. The trophic role of bacteria for a nematode community on the Brouage mudflat 14 (Marennes-Oléron-France), dominated by three species: Chromadora macrolaima (64% of 15 the abundance), Daptonema oxycerca (15%) and Ptycholaimellus jacobi (8%), was 16 determined in grazing experiments using 15 N pre-enriched bacteria. On intertidal flats, 17 seasonal, tidal and circadian cycles induce strong variations in environmental conditions. 18 Grazing experiments were performed in order to measure the effects of abiotic (temperature, 19 salinity and luminosity) and biotic (bacterial and algal abundances) factors on assimilation 20 rates of bacteria by nematodes. In order to assess simultaneously bacteria and algal 21 assimilation rates, algal abundances were modified adding 13 C pre-enriched Navicula 22 phyllepta. Assimilation rate was significantly lower at 5°C, moreover general trend show a 23 prominent temperature effect with an optimum around 30°C. Assimilation at salinity 18 was 24 ha l-0 02 93 54 2, v er si on 1 4 Ju l 2 00 8 Author manuscript, published in "Marine Biology, 154 (2008) 671-682" DOI : 10.1007/s00227-008-0960-9