|| 要旨トップ | 目次 |||日本生態学会第59回全国大会 (2012年3月，大津) 講演要旨
一般講演（ポスター発表） P3-283A (Poster presentation)
Carbon stable isotope ratios (δ13C) are widely used to trace resource transfer pathway yet δ13C variation of freshwater autotrophs has not been fully understood. We analyzed data from 42 published studies supplemented with some unpublished data to show the determinants of lotic periphyton δ13C. At large spatial scales, we observed broad differences in periphyton δ13C among biomes and consistent longitudinal variation related to watershed area. Longitudinal increases in δ13C indicated the importance of in-stream processes on lotic carbon cycles and autotroph δ13C variation. At local spatial scales, periphyton δ13C was related negatively to canopy cover and water current velocity and positively to chlorophyll a density. Autotroph δ13C varied among taxonomic groups. Cyanobacteria and red algae had significantly higher and lower δ13C than other taxa, respectively. A hierarchical model across spatial scales showed that local controls for periphyton δ13C were nested by regional controls, which suggested that productivity and CO2 availability determine δ13C. Overall our results revealed general patterns of periphyton δ13C and provided improved information for study design and use of δ13C in isotopic mixing models in lotic food web studies.