|| 要旨トップ | 目次 |||日本生態学会第63回全国大会 (2016年3月、仙台) 講演要旨
一般講演（口頭発表） F3-27 (Oral presentation)
Periphytic algae attached to a streambed substrate (periphyton) are an important primary producer in stream ecosystems. We determined natural radiocarbon abundances in chlorophyll a (Δ14Cchl) and bulk (Δ14Cbulk) of periphyton collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Periphyton Δ14Cchl values (–258‰ in April and –190‰ in October) were slightly lower than Δ14Cbulk values (–228‰ in April and –179‰ in October), but were close to the Δ14C value for dissolved inorganic carbon (DIC) (–217 ± 31‰), which is a mixture of weathered carbonates (Δ14C = –1000‰), CO2 derived from aquatic and terrestrial organic matters (variable Δ14C) and dissolved atmospheric CO2 (Δ14C approximately +30‰ in 2013). Although the bulk isotopic composition of periphyton is recognized as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89% to 95% algal carbon (derived from 14C-depleted DIC) and 5% to 11% terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).