Quantitative and qualitative changes for the sedimentary and flowing organic matter between pre and after post initial impoundment at the up and downstream of the Kase dam

We investigated the effects of sedimentary and flowing FPOM (Fine Particulate Organic Matter) at the up and downstream sites of Kase dam in Saga Prefecture before and after initial impoundment. We present main clear evidence that the nitrogen isotope ratio in sedimentary FPOM at the St. 2 and St. 3 (2.2km and 11.7km downstream from the dam) in spring of afterfollowing impoundment were was significantly higher than those that of before impoundment. After impoundment of the Kase dam, phytoplankton was increased in the reservoir and they were supplied to downstream reaches of the dam. Our results suggest that qualitative changes of sedimentary FPOM downstream of a dam by after initial impoundment was is associated with the state condition of production growth of phytoplankton in the reservoir.