Abstract:A reseach experiment on ecological effects causeed by eutrophication in an enclosure ecosystem was set up in a land-based tank at the Third Insitute of Oceanography, SOA. from May to July in 1990. The results show.In the eutrophic enclosure bag, the phytoplankton community structure gradually changed in its composition and numbers of species, resulting in phytoplankton bloom and population succession.Bloom started with diatom. Microflagell-ate and Dinoflagellates began to grow in great quantity at the end o...