¹State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China
²Zhoushan Marine Ecology Environmental Monitoring Station, Zhejiang 316000, China
³East China Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences,Shanghai 200090, China

*Corresponding author: salixly@yahoo.com.cn

Abstract

   The Changjiang River is well-known to channel significant anthropogenic influences to the estuary. However, long-term changes in plankton community related to anthropogenic eutrophication in the estuarine water are not well documented. In this paper, data from a nine year study (1996, 1998–2005) on suspended matter, chemical oxygen demand, nutrients and plankton community were collected and analyzed by principal component analysis. These data reveal that N/P ratio was always much higher than 40 and Si/N ratio decreased from 1.35 to 0.94 between 1996 and 2005. As an ecological consequence to such nutrient balance changes, phytoplankton species diversity and the dominance of diatoms decreased, dinoflagellates increasingly dominated the phytoplankton population, and the frequency of harmful algal blooms caused by dinoflagellates also increased. Furthermore, due to the reduced diatom availability, the dominance of copepods decreased, zooplankton diversity increased, and medusae increasingly dominated the zooplankton population. Water column nutrient ratios, therefore, are also important factors in affecting anthropogenic eutrophication, as are the contamination loadings from land.