北部湾海域微型、微微型浮游植物类群季节变化及其与棕囊藻赤潮的关系初探

RELATIONSHIP BETWEEN SEASONAL VARIATION OF PICO-AND NANO-PHYTOPLANKTON ASSEMBLAGES AND PHAEOCYSTIS RED TIDES IN BEIBU GULF

近年来,北部湾海域连年暴发球形棕囊藻(Phaeocystis globosa)赤潮,对近海生态环境构成了潜在威胁。为了解北部湾海域球形棕囊藻赤潮生消过程及其与其他浮游植物类群的关系,自2016年9月至2017年8月期间,在北部湾海域开展了9个航次的调查,并应用流式细胞仪分析了微型真核藻类、微微型真核藻类、原绿球藻(Prochlorococcus spp.)和聚球藻(Synechococcus spp.)等4类浮游植物类群的变化情况。结果表明,北部湾海域各浮游植物类群主要分布在调查区北部钦州湾外侧海域和雷州半岛西侧近岸海域,其丰度有明显的季节变化。微微型真核藻类在春、秋两季丰度较高,而冬、夏季较低。微型真核藻类、聚球藻和原绿球藻的丰度均呈现夏季高、冬季低的特点,其中聚球藻丰度的季节变化最为显著,与水温变化密切相关。结合对球形棕囊藻赤潮生消过程以及调查海域水文条件的分析可以看出,北部湾海域球形棕囊藻赤潮发生过程中,海水温度下降至20℃左右,并且聚球藻和原绿球藻丰度具有明显变化,有望作为棕囊藻赤潮的预警指标,为该海域棕囊藻赤潮的预测和防控提供依据。

The occurrence of red tides formed by Phaeocystis globosa in the Beibu Gulf posed significant threats to the marine environment and ecosystems.To understand the relationship between Phaeocystis globosa red tides and phytoplankton assemblages,nine cruises were conducted in this area from September 2016 to August 2017.Distribution and dynamics of four representative phytoplankton assemblages,including picoeukaryotes,nanoeukaryotes,Synechococcus,and Prochlorococcus,were studied with flow cytometry.It is found that the phytoplankton assemblages distributed mainly in the sea areas around Qinzhou Bay,and the western side of the Leizhou Peninsula.Seasonal variations of the phytoplankton assemblages were obvious.The abundance of picoeukaryote was higher in spring and autumn but relatively lower in summer and winter.The other three assemblages had higher abundance in summer and lower abundance in winter.The seasonal variation of Synechococcus abundance was similar in the variation pattern of seawater temperature.The abundance of Synechococcus and Prochlorococcus changed remarkably before and after the red tides of Phaeocystis globosa,which is due probably to their different adaptive strategies to temperature.It is suggested that temperature below 20℃and a rapid decrease of either Synechococcus or Prochlorococcus are indicators to Phaeocystis blooming,for which monitoring and early-warning of Phaeocystis red tides can be motivated.