Effect of sedimentary organic matter on species richness of deposit feeders in enclosed bay ecosystems: Insight from fatty acid nutritional indicators

How nutritional quality of dietary resources affects species richness of consumer communities is poorly understood. We used fatty acids as indicators of nutritional quality of sedimentary organic matter to evaluate the effects of highly unsaturated fatty acid (HUFA) content in sediments and fatty acid diversity in sedimentary organic matter on species richness of deposit feeders. We sampled benthic animals and sedimentary organic matter, a potential dietary source for deposit feeders, at 54 locations in two bay ecosystems. The species richness of deposit feeders ranged between 1 and 29 and had a parabolic relationship with the organic carbon content of sediments. At intermediate range of sedimentary organic carbon content, the species richness of deposit feeders was positively related to HUFA content and fatty acid diversity. These findings indicate that nutritional quality is one of the important factors determining species richness. In particular, HUFA content and fatty acid diversity are useful indicators of the nutritional quality of potential diets and good predictors of the occurrences of benthic invertebrates in marine habitats.