Community structure and environmental factors of phytoplankton in Changjiang Estuary and adjacent sea in spring and autumn

To understand the present environment quality of the marine ecosystem in Changjiang Estuary and adjacent sea,the phytoplankton community structure was studied based on data from 38 stations in autumn 2011 and spring 2012. Combined with the data of environmental factors investigation,canonical correspondence analysis( CCA) was applied to explore the relationship between phytoplankton species and environmental factors using CANOCO 4. 5. The results showed that 195 species were identified in spring,218species were identified in autumn,diatom was the dominant group,second was dinoflagellate. Skeletonema costatum was the absolutely dominant species in Changjiang Estuary and adjacent sea. The average abundance of phytoplankton was 1. 23 × 105/ L in spring,while 7. 15 × 104/ L in autumn. Concerning the horizontal distribution,the abundance was high in Changjiang Estuary in spring,and that was high in offshore area in autumn. The Shannon diversity index was 1. 59 in spring and 2. 23 in autumn. Based on canonical correspondence analysis,DSi,DIP,DIN and salinity were the main factors affecting diatom in Changjiang Estuary and adjacent sea;while transparency,salinity and DO were the main factors affecting dinoflagellate.