ORGANIC MATTER DECOMPOSITION IN THE CHANNEL AND STREAMBED SEDIMENTS AT THE DOWNSTREAM OF HEADWATER RESRVOIRS
Allochthonous organic matter decomposition is a crucial process providing matters and energy to aquatic organisms in mountain streams, and this process could be affected by dam reservoirs. In this study, organic matter decomposition rates in the wetted channel and streambed sediments were studied at the downstream of headwater reservoirs using the cotton-strip assay method. The measurement was carried out 5 times in 2016 to observe the seasonal variation, and to evaluate the contribution of aquatic invertebrate, we used two different mesh sizes housing the cotton strips. The decomposition rate was slower at the downstream of reservoirs compared to the upstream reach and the nearby tributary without a reservoir in all seasons. Though water temperature was consistently warmer, the inorganic nitrogen concentration and the contribution of aquatic invertebrate were lower at the downstream of the reservoir, which contributed to the lower decomposition rate at the downstream sites. When the wetted channel and streambed sediments were compared, the decomposition rate in the streambed sediments were lower, except for winter time, suggesting that streambed sediments become important location for decomposition in winter.
Tamao Kasahara (Primary Presenter/Author), Kyusyu University, firstname.lastname@example.org;
Yanda Li ( Co-Presenter/Co-Author), Kyushu University, email@example.com;
Noboru Fujimoto ( Co-Presenter/Co-Author), Kyushu University, firstname.lastname@example.org;
Masaaki Chiwa ( Co-Presenter/Co-Author), Kyushu University, email@example.com;