Distribution characrerstistics of size-fractionated chlorophyll a and productivity of phytoplankton in the Beibu Gulf

The distribution of the abundance of phytoplankton,chlorophyll a concentration and primary productivity in the Beibu Gulf were observed from May 23 to June 4,1994.The results showed that there were marked features of spatial zonation in the surveyed area due to the differences between the geographic environment and the hydrological conditions.Chlorophyll a and primary productivity were higher in the inshore than in the middle area and higher in the north than in the south of the Beibu Gulf.The average concentration of chlorophyll a,primary productivity (C) and the abundance of phytoplankton were 0.94±0.45 μg/dm³,351±172mg/(m²·d) and 0.97×10⁴~10050×10⁴/ind./m³ in the surveyed area,respectively.There were 176 species belonging to 4 phyla and 56 genera based on microscope identification.The average chlorophyll a of the anchor station was higher in the north (0.47±0.15 pg/dm') than that in the south (0.15±0.02μg/dm³) of the gulf.The results of the size-fractionation showed that the contribution of nanoplankton with picoplankton to total chlorophyll a was 77%,to total primary productivity was 91%,which proved their importance in phytoplankton community of the Beibu Gulf.