Distribution of Size-fractionated Chlorophyll a of Phytoplankton and Its Relationship with Environmental Factors in Zhanjiang Bay

From April to October in 2010, spatial and temporal distribution of size fractionated Chlorophyll a of phytoplankton and the related environmental factors affecting this distribution were surveyed in three seasons in Zhanjiang Bay. Total concentration of Chlorophyll a ranged from 1.75mg/m3to 4.73 mg/m3in spring,with an average of 3.05 mg/m3. Chlorophyll a of picophytoplankton accounted on average for 62.9% of total Chlorophyll a,while total concentration of Chlorophyll a varied from 8.99 mg/m3to 37.98 mg/m3in summer with an average of 21.37 mg/m3. Chlorophyll a of microphytoplankton contributed to 78.8% of total Chlorophyll a in this season. Total concentration of Chlorophyll a ranged from 2.92 mg/m3to 27.85 mg/m3in autumn with an average of 6.49 mg/m3,and Chlorophyll a of microphytoplankton accounted on average for 55.7% of total Chlorophyll a. Chlorophyll a concentration of picophytoplankton progressively increased from outer stations to inner stations,and Chlorophyll a concentration of nanophytoplankton in the core region was higher than that in the entrance region,central region and northern region. Chlorophyll a concentration of microphytoplankton in the entrance region and central region was higher than that in the core region and northern region. CCA analysis of the main environmental factors in Zhanjiang Bay showed that NO3--N and SiO3 2--Si contributed greatly to Chlorophyll a of microphytoplankton while NH4 +-N gave a great contribution to Chlorophyll a of picophytoplankton and PO4 3--P and temperature brought about more contribution to Chlorophyll a of nanophytoplankton,however suspended solids and salinity gave little contribution to the Chlorophyll a of phytoplankton.