Size Structure of Phytoplankton Community and its Response to Environmental Factors in Spring and Summer in Xiamen Bay, China

Environmental characteristics and phytoplankton size structure were investigated during spring and summer cruises in 2015 in Xiamen Bay of China. The distribution of total Chlorophyll a (Chla) showed a seasonal and spatial variation. In surface water, total Chla concentration increased from west to east in spring, while it showed the highest value in nutrient-rich West water in summer. Total Chla concentration was higher in summer than in spring. Nano-phytoplankton dominated in this study area. In spring, nano-proportion was the highest in the Jiu'long River Estuary and showed a positive correlation with nutrient in surface water. Micro-and pico-proportion were the highest in Da'deng water. In summer, nano-proportion was higher in most stations than that in spring, and micro-was on the contrary. And pico-proportion was the highest in West water. The distribution of each size-fractionated phytoplankton in bottom water was almost similar with that of surface water in these two cruises. Compared with historical data, nano-proportion increased and micro-decreased. Based on correlations between size-fractionated phytoplankton and environmental factors, nutrient availability and temperature played significant roles on size structure of phytoplankton community. Results suggested that size structure of phytoplankton community probably turned to be smaller with environmental factors changes especially eutrophication and climate warming in Xiamen Bay.