Size Structure of Phytoplankton Community and Its Regulation in Spring and Summer in Xiamen Bay, China

摘要

Environmental characteristics and phytoplankton size structure were investigated in the surface and bottom water during the spring and summer in 2015 in Xiamen bay of China.The distribution of Chla was a high degree of temporal and spatial variation in the study area.In the surface water,Chla concentration was higher in summer than in spring,with the mean of 3.26μg/L and 2.97μg/L respectively.In the spring,total Chla concentration increased from northwest to southeast,the highest total Chla was in nutrient poor water with higher contribution of microphytoplankon (48.6％).In the summer,total Chla showed higher in west than in east,causing by high nutrients in west.Total Chla showed the similar distribution pattern in the bottom water with those in the surface water in these two seasons.Nanophytoplankton was the dominated factor in these two cruises.The highest value of nano-Chlashowed in Jiu'long river estuary,while that of pico-and micro-appeared in oligotrophic Da'deng water in the spring.In the summer,size fraction phytoplankton Chla showed the highest mean in nutrient-rich West water,except for the highest value of pico-Chla was in Tong'an water in the bottom water.Nano-proportion turned to be higher from spring to summer,micro-was on the contrary in the study area.Pico-proportion was still the lowest during the two cruises.In the spring,nanoproportion showed the highest proportion in West water and a positive correlation with nutrients in the surface water,and that of micro-was in oligotrophic Da'deng water.It probably was concluded that nutrients played the major roles in nanophytoplankton growth in the spring.Compared with the historical data,it maybe proclaimed that nanophytoplankton had a stronger growth capacity in the summer in Xiamen bay.Based on correlations between size-fractionated phytoplankton and environmental conditions,nutrients availability and temperature played significant roles in size-fractionated phytoplankton growth and community structure.Phytoplankton community size structure turned to be smaller with environmental factors changes in Xiamen bay.