Size structure of phytoplankton community and its response to environmental factors in Xiamen Bay, China

To investigate the response of phytoplankton size structure to changes of environmental factors, total and size-fractionated (pico-, nano- and micro-phytoplankton) Chla concentrations were studied in autumn in Xiamen Bay of China. Total Chla concentration was higher in west area than that in east area, similar to the spatial distribution of SiO3-Si and DIN concentration. Comparing different water areas, the proportion of micro-Chla and size index of phytoplankton were highest in the Da'deng water with lowest DIN and PO4-P. The highest value of pico-Chla concentration and proportion was in the nutrient-rich West water. Compared with historical results in Xiamen Bay, nano- phytoplankton was still the dominant contributor in the bay, and pico- phytoplankton proportion increased in the West water. Besides nutrient increasing, it might be relative to global climate warming. Based on historical data from 1954 to 2010, phytoplankton community under observation of microscope also showed a miniaturizing trend. Correlations between phytoplankton and environmental factors indicated that nutrient availability, temperature and irradiance probably impacted size structure of phytoplankton community in Xiamen Bay. It implies that more studies are needed to explore how environmental factors especially eutrophication and global climate change affect size structure of phytoplankton community and the subsequent impact on the marine ecosystem structure in the future.