Preliminary estimation of the export of omega-3 polyunsaturated fatty acids from aquatic to terrestrial ecosystems in biomes via emergent insects

Abstract

Some terrestrial consumers may be limited by food quality, namely by contents of essential polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (20:5n−3, EPA) and docosahexaenoic acid (22:6n−3, DHA) in their food. Since EPA and DHA are mainly produced in aquatic ecosystems, for future estimating of the potential limitation by food quality in global scale, the water-land fluxes of these PUFA with the biomass of emergent aquatic insects in several biomes were calculated. The water /land area ratios for each biome were calculated by dividing the water area of each biome by its terrestrial area. Data on insect emergence from water bodies (g of dry mass m−2 year−1), were summarized and averaged for each biome. From available data, EPA and DHA contents (mg g−1dry mass), in the biomass of emergent aquatic insects were calculated first so that annual fluxes of PUFA to land area via aquatic insect emergence could be estimated for each biome. PUFA fluxes occurred between the biomes, ranging from 0.04 to 4.39 mg m−2 year−1. In this study, the aquatic PUFA supply to land area appeared to be significantly lower than estimated earlier. This suggests that terrestrial consumers may experience food quality limitations mediated by shortage of PUFA compounds.