Relationships between sedimentary organics and benthic meiofauna on the continental shelf and the upper slope of the Gulf of Lions (NW Mediterranean)

Abstract

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, carbohy- drate, 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 de- scriptors 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.