Sulfur stable isotope signature identifies the source of reduced sulfur in benthic communities in macrophyte zones of Lake Biwa, Japan

摘要

Carbon, nitrogen and sulfur stable isotope ratios (δ ~13C, δ ~15N and δ ~34S) were measured from water column sulfate, sediments, particulate organic matter (POM), macrophytes, periphyton, macroinvertebrates and fish, sampled from the littoral, open water and macrophyte zones of Lake Biwa. In most of the littoral zones, the δ ~13C and δ ~15N values of organisms indicated that POM and periphyton support the consumers. However, in the dysoxic interior macrophyte (IM) zone, the δ ~13C values of Sinotaia quadrata histrica, Propsilocerus akamusi and Anodonta woodiana were lower than that of all resources. The δ ~15N values of S. quadrata histrica were lower than those of P. akamusi and A. woodiana. δ ~13C and δ ~15N values thus failed to distinguish the foods of these consumers. The δ ~34S values of sediment and S. quadrata histrica were lower than those of water column sulfate, suggesting that this consumer incorporated reduced sulfur derived from sulfate reduction in the sediment by ingesting detritus. In contrast, the δ ~34S values of P. akamusi and A. woodiana were higher than that of S. quadrata histrica, suggesting that they incorporated sulfur derived from water column sulfate by ingesting POM. Consequently, δ ~13C, δ ~15N and δ ~34S signatures provide complementary estimates of foods for consumers in this freshwater lake.