PHYTOPLANKTON SIZE STRUCTURE AND ITS TEMPORAL AND SPATIAL CHANGES IN JIAOZHOU BAY

On the basis of the monthly observation of concentrations of size-fractionated Chl.a during 2003—2010,the phytoplankton size structure and its seasonal,annual,and long term changes in Jiaozhou Bay were studied.Results indicated that the micro-and nano-phytoplankton were the main components in the phytoplankton community in Jiaozhou Bay.The concentration of Chl.a decreased from the north and northeast to the middle and the south of the bay.The seasonal and annual changes of the size-fractionated Chl.a concentrations were similar in different areas of the bay.The micro-and nano-phytoplankton showed a seasonal change of double-peak,with the micro-phytoplankton peak in winter and nano-phytoplankton peak in summer.The percentage of the micro-,nano-and pico-phytoplankton in different areas were similar.The results of the long term changes indicated that the percentage of the micro-phytoplankton was increasing since 1990s in the winter,and the nano-phytoplankton percentage increases in the summer.The percentage of pico-phytoplankton significantly decreased after 2000.The temperature,the concentration and structure of nutrients were important factors affecting the change of the size fractionated Chl.a in Jiaozhou Bay.