Spatial and Temporal Variation in Stable Isotopes Signatures of Periphyton and an Endangered fish in a flow-reduced River Reach

Document Type : Original Research Paper

Authors

1 Department of urban and environment engineering, Kyushu University, Fukuoka, 8190395, Japan. China Institute of Water Resources and Hydropower Research, Beijing, 10038, China

2 Department of urban and environment engineering, Kyushu University, Fukuoka, 8190395, Japan

3 State key laboratory of hydraulics and mountain river engineering, Sichuan University,

Abstract

The environmental and ecological issues in the flow-reduced river reach are very serious and are
receiving increasingly attention. In this study, we investigate the temporal and spatial changes in δ13C and δ15N of Periphyton and isotopic relationship between Periphyton and the endangered fish (Ayu, Plecoglossus
altivelis) in a flow-reduced river reach in Japan. Much of the spatial and temporal variation in δ13C of
endangered fish was explained by variation in Periphyton, indicating a strong link between primary production and higher order consumers. The Periphyton δ13C was correlated with current velocity while it was not correlated with the Periphyton biomass (Chl.a). Spatially, the relatively high δ13C and δ15N of Periphyton in the lower sites of the flow-reduced river reach might be due to high level of anthropogenically derived N and C introduced from the surrounding agricultural activities and human settings. The trophic position of the endangered fish in was estimated to be 1.5-2.2(1.8±0.3), which agrees with the previous stomach content analysis suggesting that the ayu mainly feed on Periphyton.

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