不同外源营养负荷对浮游藻类群落结构特征的影响

为研究不同外源营养负荷对水体浮游藻类群落结构特征的影响, 于2010年12月至2012年6月在亚热带长江流域的4个池塘中开展了氮磷营养添加实验。实验设置4个处理, 即加氮加磷(+N+P)、只加磷(?N+P)、只加氮(+N?P)和氮、磷都不加(?N?P)(对照)。从种类来看, 各种处理对浮游藻类种类数的影响不大, 各处理中种类数相差不多, ?N+P、+N+P、+N?P和?N?P处理中浮游藻类种类数分别为75种、79种、75种和75种。各处理均是绿藻门种类最多, 其次是蓝藻门。从功能群来看, ?N+P处理的中、富营养型藻类占比和+N+P处理的相差不多, 二者均高于2个未加磷处理(+N?P和?N?P处理)的。+N?P处理的贫营养型藻类占比比+N+P处理的高, 甚至高于?N?P处理的。研究结果表明减氮不能控制藻类群落的中、富营养型藻类数量, 只控磷能够推动浮游藻类群落从中-富营养型向贫营养型演替。这一结论有望为制定富营养化治理的氮管理策略提供一定的理论依据。

EFFECTS OF DIFFERENT EXTERNAL NUTRIENT LOADING ON CHARACTERISTICS OF PHYTOPLANKTON COMMUNITY STRUCTURE

To test the effects of different external nutrient loading on characteristics of phytoplankton community structure, a whole-ecosystem nutrient addition experiment was conducted in 4 ponds located at the Yangtze River Basin from December 2010 to June 2012. Four treatments were set to represent various nutrient loads, namely both nitrogen (N) and phosphorus (P) addition (+N+P), P addition (?N+P), N addition (+N?P), and no nutrient addition (?N?P) (Control). In terms of species number, all treatments showed similar characteristic with the species number of 75, 79, 75 and 75 in ?N+P, +N+P, +N?P and Control respectively, and Chlorophyta were the dominant taxonomic group followed by Cyanophyta. In terms of functional group, the percentage of meso-eutrophic species in ?N+P was similar to that in +N+P, both were higher than the two treatments without adding P. The percentage of oligotrophic species in +N?P was higher than that in +N+P treatment, and even higher than the Control. The above results suggest that the reduction of nitrogen cannot control the percentage of moso-eutrophic species of phytoplankton, while the reduction of P can induce the succession of phytoplankton community from a meso-eutrophic type to an oligotrophic type. These results provide theoretical foundation for N management strategy in mitigating eutrophication to a certain extent.