富营养化水体降磷对浮游植物群落结构特征的影响

浮游植物是水生态系统中物质循环和能量流动的基础,作为初级生产者,浮游植物的群落结构直接影响着水生态系统的结构和功能。在水产养殖生产中,如何根据养殖生物对生活环境的需求开展精准培水、定向培水,培养养殖生物所需要的浮游植物,在维持养殖水域生态平衡的同时又能为养殖生物提供一定的饵料资源,这一直是摆在水产科技工作者面前的重要难题和研究热点。已有的资料大都是通过添加磷的方式研究磷改变对浮游植物生长的影响,而有关富营养化水体降磷对浮游植物群落结构影响的研究尚未见报道。为此,试验通过向取自富营养化湖泊的水体中加入磷去除剂,采用Pielou均匀度指数、Mcnaughton优势度指数和Shannon多样性指数,研究自然水体中的磷被降低后水体浮游植物群落结构的变化情况。结果表明,所取富营养化水体中共检出绿藻（Chlorophyta）、硅藻（Bacillariophyta）、蓝藻（Cyanophyta）、裸藻（Euglenophyta）、隐藻（Cryptophyta）、甲藻（Pyrrophyta）6门29种（包括变种和变型）;其中绿藻、蓝藻、硅藻、隐藻、裸藻、甲藻分别有7、4、2、1、1种,分别占总种数的24.13%、13.79%、6.90%、3.45%、3.45%。富营养化水体降磷后,虽然试验组和对照组在浮游植物种类组成上没有差异,但浮游植物群落结构特征发生了很大变化,浮游植物数量明显降低,由13 238.8×104cells·L-1降低至3 997.5×104cells·L-1,下降了69.8%;浮游植物优势种从1门（蓝藻（Cyanophyta））6种增加到3门（绿藻（Chlorophyta）、硅藻（Bacillariophyta）、蓝藻（Cyanophyta））12种,优势度指数从97.29%降低至86.30%,优势种门数和优势种种数远远高于对照组,优势度明显低于对照组;同时,浮游植物多样性指数和均匀度分别从1.85和0.38升高至2.60和0.54,显示出试验组浮游植物多样性和均匀度优于对照组。研究表明富营养化水体降磷对浮游植物群落结构产生了明显影响,使群落结构处于更加复杂、完整和稳定的状态。

Effect of decreasing phosphorus in eutrophic water on the community structure of phytoplankton

Phytoplankton is the base of material recycle and energy flow in aquatic ecosystem. As the primary producer, the community structure of phytoplankton influences the structure and function of aquatic ecosystem directly. In aquaculture research field, how to cultivate fish needing phytoplankton, which can maintain the ecosystem balance of aquaculture water area and provide food for farming fish, has been always an important problem and research hotspot. The effect of phosphorus change on the growth of phytoplankton had been researched by the method of adding phosphorus to test water. However, the effect of decreasing phosphorus in eutrophic water on the community structure of phytoplankton has not been reported yet. The effect of decreasing phosphorus in eutrophic water on the community structure of phytoplankton was researched by adding phosphorus removing agent to test water sampling from eutrophication lake and by the method of Pielou uniformity index, Mcnaughton predominance index and Shannon diversity index. Results showed that there were 6 classes including 29 species of phytoplankton had been recorded in the test water sampling from Lake Wuli. Among them, Chlorophyta was the predominant species, which had 14 species, accounted for 48.28% of the total species. Cyanophyta, Bacillariophyta, Cryptophyta, Euglenophyta, Pyrrophyta were recorded 7, 4, 2, 1, 1 species and accounted for 24.13%, 13.79%, 6.90%, 3.45%, 3.45% respectively. There no difference in the number of phytoplankton species, but the community structure of phytoplankton changed significantly after the phosphorus in eutrophic water was decreased. And the quantity of phytoplankton decreased significantly from 13 238.8×104cells· L-1to 3 997.5×104cells· L-1, and the decrease ratio was69.8%. The predominant species increased from 1class（Cyanophyta） including 6 species to 3 classes（Chlorophyta, Bacillariophyta,Cyanophyta） including 12 species and the predominance index decreased from 97.29% to 86.30%, which meant the class and species of phytoplankton in test group were all larger than that in the control group and the predominance index of phytoplankton in test group was lower than that in the control group. The diversity index and uniformity index of phytoplankton changed from 1.85 to 2.60and from 0.38 to 0.54 respectively, which meant the diversity index and uniformity index of phytoplankton of test group were all better than that of the control group. It would be concluded that the community structure of phytoplankton was more complex,integrated and stable after the phosphorus in eutrophic water was decreased.