人工基物上に形成される付着藻類相に与える下水処理水の影響

Abstract

Effects of sewage effluent on periphytic algae in the River Tsunaki were surveyed using artificial substrata in weekly during summer in 1996. The artificial substrata were settled at 2m upper and 2m downstream site of the discharging point. After two weeks they were exchanged to clarify the influence of sewage on the periphytic algal community succession. Water quality were surveyed at three stations, artificial substrata settling sites and discharging point.The average concentrations of BOD were 0.7 (downstream site), 0.8 (sewage effluent) and 1.1mg/l (upstream site) . The many nutrient concentrations were constantly high at downstream site by the sewage effluent.Different algal communities were formed on artificial substrata at the upper and down site. Of fifty algae recorded, Nitzschia amphibia (at the upper site) and Stigeoclonium spp. (at the down site) were dominant.Nitzschia amphibia is eurysaprobic species and Stigeoclonium spp.is a tolerant species for pollution. It was found that after forming the stable periphytic algal communitiy the sewage didn't influence the algal succession on artificial substrata. The successions of algal periphytic community on artificial substrata exchanged between the upper and down sites after two weeks reflected the enviromnent before the exchange. But the diversity index of them were down by the sewage eflluent.