Zooplankton community in Yangtze River Estuary and adjacent sea areas after the impoundment of the Three Gorges Reservoir

Abstract

Zooplankton is an important component of aquatic ecosystems and community variation reflects environmental changes. The impoundment of the Three Gorges Reservoir (TGR) has dramatically altered hydro-environmental conditions from hydrological regimes to water quality, which may have a serious impact on the estuarine ecosystem. This study analyzed the characteristics of the zooplankton community as well as their relationships to hydro-environmental factors in the Yangtze River Estuary (YRE) and the adjacent sea areas using the data after TGR impoundment. The historical zooplankton data over the past 30 years were also collected from the literature to explore long-term changes of the zooplankton community by the Mann-Kendall test. The results show that the dominant species were Noctiluca scintillans and Calanus sinicus in spring, Acartia pacifica in summer, and Paracalanus aculeatus in autumn. The most important environmental factors affecting the zooplankton community for the whole year were salinity and temperature of the bottom layer, which were largely influenced by river discharge and thus by reservoir regulation. Combined with the long-term historical data, the biomass and population density of zooplankton showed an increasing trend, and the community structure of zooplankton also shifted over the past 30 years.