Abstract
Dams often supply large amount of Fine Particulate Organic Matters (FPOM) orginated from dam reservoirs (called "dam-POM") to their downstream reaches. It potentially leads to a shift of trophic sources of stream faunal communities from the stream-origins (e.g., periphyton and terrestrial input) to the dam-origin organic matters. However, the lentic habitats at dam outlet reaches such as backwater and isolated pool may receive a lot of terrestrial and autochthnous organic matters, thus we need habitat-specific tests regarding the trophic dependency on dam-POM. The aim of this study is to qularify the spatial variation of trophic contribution of dam-POM between lotic and lentic habitats at dam downstream reaches. The proportion of contribution of dam-POM to Suspended FPOM and Benthic FPOM was quantified at each habitat using a mixing source model with carbon and nitrogen stable isotopic data. The results support the habitat specific patterns showing higher contribution of dam-POM to Suspended FPOM in lotic habitats than lentic habitats. It suggests the ecologically important role of lentic habitats in locally sustaining insitu trophic structures of stream ecosystem in the impacted reaches by dams.
