The characteristics of eutrophication and its correlation with algae in chongming island's artificial river network

Abstract

In order to study the trophic status of rivers in Chongming Island, the temporal and spatial variations of environmental factors and their interaction mechanisms in the main rivers were investigated. Results showed that eutrophication was present in the main rivers of Chongming Island. The concentrations of nitrogen and phosphorus in the main rivers were high, and nitrogen pollution was particularly severe. In fact, those nutrients mainly originated from the Yangtze River, rather than the local source in this island. Except for in winter, the chlorophyll-a content in most of the main rivers reached some level of eutrophication. The appearance of phosphorus promoted the growth of algae; this was due to water from the Yangtze River entering the main rivers. The evolution of the algae population accorded with the PEG model, as follows: winter (diatom), spring (chlorophyta and diatom), summer (cyanobacteria and chlorophyta), and fall (diatom). In addition, the trophic state index (TSIM) indicated that rivers were at the "heavy eutrophication" level in spring and summer, and the "eutrophication" level in winter and autumn. In summer, chlorophyll- a and TP were the main contributors to the trophic status of the rivers.