Zin'ichi Karube; Naoki Okada; Ichiro Tayasu
LIMNOLOGY 13 3 269 - 280 2012年12月
[査読有り] Carbon, nitrogen and sulfur stable isotope ratios (delta C-13, delta N-15 and delta S-34) 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 delta C-13 and delta N-15 values of organisms indicated that POM and periphyton support the consumers. However, in the dysoxic interior macrophyte (IM) zone, the delta C-13 values of Sinotaia quadrata histrica, Propsilocerus akamusi and Anodonta woodiana were lower than that of all resources. The delta N-15 values of S. quadrata histrica were lower than those of P. akamusi and A. woodiana. delta C-13 and delta N-15 values thus failed to distinguish the foods of these consumers. The delta S-34 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 delta S-34 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, delta C-13, delta N-15 and delta S-34 signatures provide complementary estimates of foods for consumers in this freshwater lake.