Influence Of Sediment Process Variation On Phytoplankton In The Three-gorges Reservoir And A Eutrophication Assessment Methodology

The construction of the Three－Gorges Reservoir changed the hydrology andwater dynamics of the river upstream and downstream of the reservoir． Thesechanges and adjustments inevitably affect the habitat of aquaticorganisms． Phytoplankton distribution within the reservoir is influenced bysediment， hydrology， and other conditions， including total phosphorus， totalnitrogen， pH， temperature， and turbidity． Phytoplankton serves the role of themost influential primary producers in aquatic habitats． The structure and quantity ofphytoplankton greatly influence the successional development of water ecosystems．The influence of various factors on phytoplankton density and biomass in waterbodies was analyzed based on the Three－Gorges Reservoir monitoring data obtainedfrom November2006－November2007． The water quality variables measuredincluded Chl－a， total phosphorus， total nitrogen， sediment content， acidity，water temperature，dissolved oxygen，and electrical conductivity．The main factorsinfluencing phytoplankton abundance included sediment， dissolved oxygen， andtemperature． Quantitative and interactive relationships among the main factors wereexamined using the response surface methodology． The water index in the Three－Gorges Reservoir was cluster－analyzed， thus revealing that the trunk stream of theChangjiang River can be divided into two clusters： the upper river areas includeChaotianmen， Fulin， Shizhu， Zhongxian， and Wuyang， whereas the downriverareas include Wanzhou， Wushan， Fengjie， Yunyang， Badong， and Zigui． Theregression relationship between chlorophyll－a and nutrients was determined basedon the characteristics of the river channel component of the Three－GorgesReservoir． The nutrient level of each region was evaluated by the weightedcorrelation of the comprehensive nutrient index． The reservoir was observed to beoligotrophic． Compare the result with that of biological evaluation and theadvantages of the weighted correlation of the comprehensive nutrient index wereindicated．...