台湾海峡南部上升流区浮游植物对磷的响应

Response of phytoplankton to phosphorus in the upwelling zone of southern Taiwan Strait

取台湾海峡南部近岸上升流区表层海水,开展现场船基围隔实验.按照上升流区底层无机形态氮、磷和硅的浓度及比例,设置围隔袋中营养盐浓度,研究上升流输入的营养盐可能对海区表层浮游植物生物量及群落结构的影响,结合群体方法与单细胞酶标记荧光技术,检测浮游植物的碱性磷酸酶活性,指示海区浮游植物的磷营养生理状态.结果表明,营养盐的补充导致中肋骨条藻(Skeletonema costatum)、角毛藻(Chaetoceros spp.)、冰河拟星杆藻(Asterionellopsis glacialis)、菱形海线藻(Thalassionema nitzschioides)和尖刺拟菱形藻(Pseudo-nitzshcia pungens)等硅藻成为优势种,并形成藻华.随环境中营养盐的耗尽,硅藻藻华迅速消退.上升流的形成及其减弱、消失,造成表层海水营养盐水平的改变,是导致此次硅藻藻华生消的主因.通过上升流补充的磷源不足以满足浮游植物的生长需求,海区浮游植物的生长遭受磷胁迫,磷成为该海区浮游植物生长的主要营养盐限制因子.

The surface seawater from the upwelling zone of the coastal southern Taiwan Strait was collected to carry out the in situ mesocosm experiment on board. Different forms and concentrations of nutrients were added to mesocosm bags based on the principle of nitrate, phosphate and silicate concentrations and their ratios were detected from the bottom layer of the upwelling zone. The effects of nutrients on the growth of phytoplankton and the community structure during the upwelling were studied. Both the bulk assay and the single-cell enzyme labeled fluorescence method were used to detect the alkaline phosphatase activity of phytoplankton and to indicate the phosphorns status of algae. Results showed that Skeletonema costatum, Chaetoceros spp. , Asterionellopsis glacialis, Thalassionema nitzschioides and Pseudo-nitzshcia pungens became the dominant species and bloomed in the nutrients supplementary experiments. However, the diatom bloom soon collapsed after nutrients were depleted. The variation of nutrients induced by the formation, weakening and disappearance of upwelling was the principle factor for the performance and collapse of the diatom bloom. The phosphorus supplied by the upwellingcould not sustain the growth of phytoplankton and algae still under phosphorus stress. This indicates that phos- phorus might be the limiting factor for primary production in this area.