The Ecological Characteristics Of Rotifer Community In The Yangtze River Estuary

Rotifers play an intermediate role in the food web in the water ecological system.Their composition and community structure are influenced by nonbiological factors,such as salinity, temperature, and sediment contents. Thus, the trends can reflect thechanges of the water environment.Since the1990s, the influence of human activities on ecosystems has beenincreasing. Big projects, such as Deep Waterway Project, Three Gorges Dam, and theSouth to North Water Diversion Project have changed the hydrological conditions ofthis estuary, as well as the ecosystem a lot. This work is intended to clarify theecological status of rotifers after the construction of those big projects.Rotifers were collected monthly from the south (4/2009to4/2010), and the north(10/2010to9/2011) branches of the Yangtze River estuary. Samples from bothbranches were also collected in August and September2010. Based on the rotifercommunity composition, density, and community diversity analysis, the characteristic-s of rotifer community of the Yangtze River estuary were studies. The conclusions areas followed:1. Totally,9families including34genera, and86species of rotifers were collected inthe surf zone of Yangtze River estuary. The dominant species were Lepadellapatella, polyarthra trigla, Monostyla lunaris, Ascomorpha saltans and Keratellaticinensis. The stations which have similar hydrological conditions indicatesimilar community compositions.. The densities of rotifers showd clear seasonalvariation: spring <winter<autumn<summer. The species composition andcommunity structure were positively correlated with the water temperature,transparency and the DO value of water.2.8families including10genera and14speciesof rotifers were collected from both branches of the Yangtze River estuary in August2010, and eight familiesincluding18genera and24species in September2010. The density and diversityof rotifers from the south branch was obviously higer than that from the northbranch. The density of rotifers varied with layers: the layer which is closer to thesurface shows larger density of the rotifers. The density of rotifers were positivelycorrelated with content of chlorophylla and the temperature, but negativelycorrelated with the water turbidty and salinity.3.6families including18species of rotifers were collecter from the five stations inthe north branch. The destiny of rotifers varied seasonally: autumn>summer>spring>winter. The common species were polyarthra trigla and Ascomorphasaltans. Due to the intravison of seawater, the salinity of the north branch changesdramastically, this adversely affects rotifers and results to the low density ofrotifers. Salinity is the key facter that influences thedistribution of the rotifers.In this paper, the rotifers of the Yangtze River estuary were studied to make surethe constructions and the species now, and will take a basic for the future studying inthe zone of the Yangtze River estuary.