大亚湾拟菱形藻水华及其在生物群落中的生态地位

对2000年4~5月藻类水华高发期大亚湾澳头海域的拟菱形藻进行逐日调查,并对其与浮游植物、浮游动物的相关关系进行分析.调查初期,整个生物群落的种类组成数量都相对贫乏;拟菱形藻数量急剧增长,最高的测站密度可达2.93×106个/dm3.拟菱形藻水华的组成种类有拟极细拟菱形藻和尖刺拟菱形藻两种,以尖刺拟菱形藻稍占优势.水华形成中其他种类硅藻和甲藻在种类组成和数量上也有一定程度的增加.分析表明,拟菱形藻在浮游植物群落的种间竞争中具有优势,并成为春季硅藻水华的最重要的组成者.桡足类等浮游动物对拟菱形藻的下行控制并不能明显抑制拟菱形藻的增长及水华的产生,这与其偏爱以其他种类藻类为食有关.以上因素外加拟菱形藻对环境的广泛适应性促使其在该水域成为最常见的赤潮生物之一.

Pseudo-nitzschia bloom and its ecological role in the biological community in the Daya Bay, the South China Sea

Population densities of genus Pseudo-nitzschia,phytop lankton and zoop lankton were investigated daily from Apirl to May,2000,in the Daya Bay,the South China Sea,and relationships among these characteristics were also analyzed.The results show that at the beg inning of survery,species composition and densities of planktonic community were both rare followed by a rapidly increasing growth of Pseudo-nitzschia with a highest density of 2.93×10⁵ cells/dm³ which have reachecd the bloom density.P.pseudodelicatissmia and P.pungens were the joint-causative species as well as species composition and densities of diatom and dinoflag llate enriched during the bloom.It was found that Pseudo-nitzschia became the most miportant component in the spirng diatom bloom due to its advantage in the competition among the different species.The effect of zoop lankton's (especially copepods) down-control on Pseudo-nitzschia was't obviously mostly because of the less grazing pressure.The reasons mentioned above made Pseudo-nitzschia abundant and it a potential bloom-causing species in the study area.