The Community Structure Of Phytoplankton In Gouqi Island

The relationship of community structure of phytoplankton and the affecting factors were discussed beginning with the abundance and diversity of phytoplankton, combined with the depth, temperature, salinity, turbidity, dissolved oxygen, light quantum and other environmental datas and as well as the influential factors such as the velocity and breed aquatics of mussel. Based on the datas above, Through finding out the rules of phytoplankton's community structure and nailing down the annual change trend of biological and abiotic factors, The primary factors influence phytoplankton are concluded by correspondence analysis and principal component analysis the phytoplankton and influence factors. Meanwhile, according to the different habitat, the article compare community structure of phytoplankton to other habitats and clear out the difference between each habitat.The investigation was carried out in Gouqi Island bimonthly since July 2009, ten stations were selected which included seven conventional stations belong to four kind of habitat (beach, seaweed, rock, mussel farm). The species and quantity data of phytoplankton was gained by microscopic counting. 117 species have been identified, including 109 species diatoms which taken up 93 percent of the total species, and eight species of din flagellate. The average abundance of phytoplankton was 57.3×10~5cell/m~3, the Shannon-wiener index was between 1.48 to 2.48, and the average level was 1.86. The most species was found in September 2009, was 98 species. The highest abundance was founded in September 2009 too, was 262.1×10~5cell/m~3. The most prominent species throughout the year was Pseudo-nitzschia pungens, the average abundance of it was 32.6×10~5cell/m~3, which was reach to 60 percent of all the species'total abundance in the seven months, it has occupied the dominant position absolutely. The abundance of Pseudo-nitzschia pungens was far more than Skeletonema costatum, which abundance was 8.7 percent of the total species. The Pseudo-nitzschia pungens was bloom in September 2009, which abundance was reach to the highest 198.4×10~5cell/m~3, it's abundance was accounted for 78 percent of the total species in September 2009, and 86.9 percent of the total abundance of Pseudo-nitzschia pungens throughout the year. The distribution of phytoplankton were also different for different habitats which including seven stations. The abundance in rocks habitats was the highest, while the lowest was seaweed. The number of species was floated from 53 to 68.5. Where the diversity achieved the highest pot was in and out of the mussel farm, second in beach, and the lowest was seaweed.The growth of phytoplankton was great affected by environment factors. The temperature was the greatest impact factor to the community structure of phytoplankton by canonical correspondence analysis with the data of species and environment factors. The Pseudo-nitzschia pungens which has the most abundance was affected by temperature and turbidity. Pseudo-nitzschia pungens was affected by salinity when the temperature was appropriate, and it was affected by turbidity throughout. There were great area of mussel culture zone by floating. The species of mussel were Mytilus edulis and Mytilus coruscus, and the dominated was Mytilus edulis. The area of culture zone was eleven thousand eight hundred and twenty acres, there were seven hundred and fifty fish farmer involved in the production, and the yield of Mytilus edulis was thirty seven tons. The mussel was cultivated begining at the end of August, the weight of mussel remained unchanged from December to next February, because to the low temperature, while it glowed rapidly from March to July, the mussel was harvested by September. The organic detritus and phytoplankton was absorbed by water treatment through the growth of mussel. It was founded that the mussel has no influence to the abundance of phytoplankton by principal component analysis which compare to the data of three stations of seven months. The species number and diversity was influenced by mussel by the redundancy analysis using the mussel as a single variable. In the investigation, seven stations were set around the mussel culture zone, which divided into two parts, there were three stations in the mussel culture zone while two alongshore outside and two away from the shore outside of the zone. The principal component analysis was also been used to tested and verified that conclusion that the mussel have no influence to the abundance of phytoplankton.