Abstract:

Diatom，as a kind of autotrophic photosynthetic eukaryotic algae，is an important primary producer in aquatic ecosystem，and can reflect the average status of water environment. Diatoms are widely used in stream bioassessment due to their broad distribution，extraordinary variability and the ability to integrate changes in water quality. The indices of Specific Polluosensitivity Index (SPI)，standardized Biological Diatom Index (BDI)，European Economic Community Index (CEC) and Generic Diatom Index (GDI)，originally developed in France，are often applied to evaluate stream ecological quality based on diatom communities. Diatom assemblages were collected from 18 sampling stations in the Jinhua River Basin in July 2012. Dissolved oxygen，pH，total phosphorus，total nitrogen，chemical oxygen demand，ammonium nitrogen，and biochemical oxygen demand after five days were measured. A total of 75 taxa were identified，belonging to 2 classes，12 families，30 genera. The similarities and differences were compared between diatombased method and physicochemical method. The physicchemical parameters showed that the water quality level was from Grade I to Grade V，while diatom index showed its quality was at medium level or above the medium. These two assessment results were almost identical as a whole although differences between them did occur. For diatom ecotype，the results showed that all sites were dominated by circumneutral，oligosaprobous and βmesosaprobous，Nautotrophic，continuously high aerobic diatom taxa. There were negative significant relationship between SPI and permanganate index and nitrate nitrogen. There was negative significant relationship between BDI and ammonia nitrogen. The results of the present study provide a good experience for biomonitoring in the Jinhua River Basin,but more researches are needed in order to establish Chinese biomonitoring standard