Study On Eutrophication Assessment Of Changjiang Estuary Area And The Selection Of Bio-indicators

Eutrophication has become a global environment problem. The eutrophicationproblems of Changjiang Estuary, which is the biggest estuary in China, became moreand more prominent these days. It is urgent to find a credible way to prevent and solvethe eutrophication problems of Changjiang Estuary. So it has an important meaning tonicely evaluate the eutrophication degree.Based on the 8 quarter's field investigations during 2004 and 2005, the authoranalysis the eutrophication degree of the Changjiang Estuary. The author also carriedout indoor simulation culture experiment to find a physiological-biochemicalcharacteristic criterion of micro-alga which can reflect the nutrient status of theenvironment.The author analysis the Eutrophication status of the Changjiang Estuary duringthe 2004 and 2005 and evaluated the eutrophication level by using fuzzy synthesis. Itcan be concluded from the results as follows:â‘  The DIN of these areas is at a higher level, which is the main pollutant. Theindex mark of others are all at better level;â‘¡ About half the sampling sites are at the stage of eutrophication. The outletsand the dilution zone of Changjiang river are characterized as eutrophication.The off-sea of Changjiang estuary is at the oligotrophic stage. Theeutrophication levels are gradually increased from off-sea to offshore.â‘¢ Most of all the areas charactered as eutrophication are belong to that salinitybelow 20. The obvious seasonal and regional variability showed that, theeutrophication levels of this area are dominated by Changjiang river dilutedwater.The indoor simulation culture of Skeletonema costatum and the elementaryresearch of the relationship between the physiological-biochemical indicators ofmicro-alga and the nutrient status of the environment showed:â‘  The nutrient status of the environment influence most of thephysiological-biochemical indicators of plankton. Different original concentrationof N and P causes difference indicator value. Different original N/P ratio leads thesame result.â‘¡cncentration of chla and alkaline phosphatase (AKP) activity of the alga cellularand the RNA/DNA ratio have an evident response to the eutrophication degree ofthe environment, which have possibility to indicate the eutrophication degree andneeds to be studied further.