The Study On Phytoplankton Ecology In Rushan Bay And Its Adjacent Area In Spring And Autumn

According to the investigation in Rushan Bay and its adjacent area in spring andautumn2011, the ecological characteristics of phytoplankton community wereanalyzed in this paper, and compared the difference between inside and outside ofRushan Bay and seasons. Aim to know the effect on gulf ecosystem under thedisturbance of human, and provide basic materials for environment protection.Sampling methods include water collecting and net tow for quantitative andqualitative study, respectively.A total of101species which belong to51genera of4phyla were identifiedthrong collected samples from spring and autumn, including90species ofBacillariophyta(89.11%),9species of Pyrrpphyta(8.91%),1species ofChrysophyta(0.99%),1species of Xanthophyta(0.99%). The cell abundance ofwater-phytoplankton ranged from1.05to50.45×10~6cells/m~3, with an average of11.53×10~6cells/m~3during two seasons. The cell abundance of diatom took apercentage of98.43in total cell abundance with an average of11.35×10~6cells/m~3. Thecell abundance of net-phytoplankton ranged from1.39to47.03×10~4cells/m~3with anaverage of13.75×10~4cells/m~3. Tthe cell abundance of diatom took a percentage of88.41in total cell abundance with an average of12.16×10~4cells/m~3. Diatom was thedominant group both in cell abundance and species richness in survey area.The cell abundance of phytoplankton in autumn was higher than it in spring, thecell abundance in surface water and net-phytoplankton inside of Rushan Bay washigher than it outside of it in spring and autumn. The cell abundance in bottom waterinside of Rushan Bay was lower than it outside of it in spring, while higher in autumn.The change of diatom cell abundance is consisntent with the total cell abundance.There were evident differences for dominant species between two seasons. The dominant species were Skeletonema costatum, Thalassiosira nordenski ldii, Nitzschiaspp, Pinnularia spp, Pleurosigma spp, Pleurosigma spp, Synedra spp, Noctilucascintillans, Chaetoceros densus in spring, Skeletonema costatum, Pleurosigma spp,Synedra spp, Pleurosigma spp, Chaetoceros lorenzianus, Coscinodiscusasteromphalus, Noctiluca scintillans and Thalassiothrix frauenfeldii in autumn.The Shannon-Wiener index ranged from0.52to3.86with an average of1.90during two seasons, the average of spring was1.74, the average of autumn was2.05,the value of autumn was higher than it of spring. The Pielou evenness index rangedfrom0.11to0.93with an average of0.61, the average of sping was0.66, the averageof autumn was0.55, the value of spring was higher than it of autumn. The Margalefindex ranged from0.59to4.71with an average of2.45, the average of spring was2.14, the average of autumn was2.76, the value of autumn was higher than it ofspring. The lower species diversity index showed that the survey area was polluted.The results of community similarity cluster analysis showed that there weredifferent community characteristics between inside Rushan Bay and outside of it innet-phytoplankton of sping and autumn and water samples of autumn. The cellabundance in surface water showed a highly significant positive correlation withnitrate and a highly significant negative correlation with DO (P＜0.01), and the cellabundance of net-phytoplankton showed a significant positive correlation withtemperature and phosphate (P＜0.05) in spring. The cell abundance in bottom watershowed a significant negative correlation with temperature, and the cell abundance ofnet-phytoplankton showed a highly significant negative correlation with salinity, anda highly significant positive correlation with nitrate in autumn.