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Gross sedimentation rates (GSR) were monitored together with the main characteristics of the collected matenal (i.e. organic content, C, N, total proteins, lipids, carbohydrates, available proteins and amino acids) over a 2 yr cycle at a shallow station (18 m) of the bay of Banyuls, France. In addition, sediment pigment concentrations and meiofaunal densit~es were recorded monthly during a 1 yr period. GSR ranged between 0.6 and 317.8 g DW m ' cl'' Spring and summer were characterized by relatively low and constant GSR whereas fall and wlnter were characterized by relat~vely high and hlghly variable GSR. There was a negatlve relationship between GSR and the organic content of material collected within the sediment traps, suggesting the importance of resuspension in controlling GSR. Growth rates of the deposit-feeding bivalve Abra ovata fed sediment trap material collected on 6 sampling dates were also measured. Significant changes in important nutrient components (e.g. available proteins) of sedimenting materials from these different sampling dates correlated with growth differences and confirmed the existence of temporal changes in the quality of the material collected in the sediment traps. The highest growth rate was obtained for the material collected during May 1993, which coincided with maximal meiofauna densities and maximal pigment concentrations at the surface of the sediment. The best descript.ion of growth was obtained when using available proteins and total lipids as the independent variables of simple linear regression models. This supports the use of these parameters as descriptors of food quality. The consequences of our results on the parameterization of changes in food quality within models of continental shelf food webs are discussed. It is suggested that such changes should be simulated through control functions based on available protein contents.

The relationships between the biochemical characteristics of sedimentary organics and benthic meiofauna in the Gulf of Lions were assessed based on samples collected at 19 sites during June 1998. We measured sediment granulometry, organic matter, organic carbon, nitrogen, carbohydrate, lipid, total hydrolyzable amino acid (THAA) and enzymatically hydrolyzable amino acid (EHAA) concentrations together with C/N and EHAA/THAA ratios. Meiofauna abundance and nematode biomass were also analyzed. All biochemical parameters showed the same pattern of change relative to depth, with a decrease between 0 and 175 m, a subsequent increase between 175 and 900 m and a final decrease at greater depths. This pattern was linked to sediment granulometry and more specifically to the occurrence of coarser sediments near the edge of the continental shelf. In contrast, meiofauna abundance and nematode biomass constantly decreased with depth. This suggests that organic matter availability does not control the quantitative characteristics of benthic meiofauna over the whole range of sampled depths. The relationships between biochemical descriptors of sedimentary organics and quantitative characteristics of benthic meiofauna were assessed in the 0 to 175 m depth range. Lipids and to a lesser extent EHAA correlated better with meiofauna abundance and nematode biomass than nitrogen, carbohydrates and organic contents. These results are discussed in view of the identification of biochemical descriptors of the nutritive value of sedimentary particulate organic matter. KEY WORDS: Particulate organic matter · Meiofauna · Gulf of Lions · Continental shelf · Continental slope Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 234: [85][86][87][88][89][90][91][92][93][94] 2002 mented the quick arrival of fresh phytodetritus at the bottom-sediment interface at depths sometimes even exceeding 5000 m (Hecker 1990, Smith et al. 1996. The occurrence of quick sedimentation processes, allowing for the presence of fresh material at the watersediment interface, raises the issue of the assessment of POM nutritional value.A proportion of the sedimentary POM corresponds to refractory forms that cannot be absorbed by benthic organisms because of the characteristics of their digestive systems (Plante & Jumars 1992, Plante & Shriver 1998. It thus seems essential to assess the particular fraction of POM that is available to benthic fauna to describe the interactions between these 2 compartments. A possible approach consists in mimicking digestion using enzymatic hydrolysis (Mayer et al. 1986, Lan & Pan 1993, Dell'Anno et al. 2000. Based on the comparison between the biochemical composition of benthic primary consumers and their primary food sources, Phillips (1984) suggested that benthic detritivores may be limited by the availability of specific micronutrients (such as essential amino and fatty acids) rather than by bulk nutrients (such as carbon and nitrogen). This hypothesis was later supported by the...

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