梯级水库影响下南渡江干流浮游生物种群洪枯水期沿程变化

为探讨河流浮游生物种群的沿程变化，针对我国唯一一条大型热带河流-海南南渡江进行生物监测和调查研究。生物监测分丰水、枯水两期开展，共鉴定出浮游植物7门151种，丰度为2.62×105~26.25× 105 cells/L，香农-威纳生物多样性指数为1.4~2.9；同站点共鉴定出浮游动物5门74种，丰度为0.01~ 157.5 ind./L，香农-威纳生物多样性指数为1.4~2.6。 研究结果表明，南渡江浮游生物群落结构沿程变化受梯级水电建设影响较大，水库浮游生物丰度一般高于河流干流。尽管热带河流气温季节变化不大，丰水、枯水水量变化对浮游生物群落影响显著。枯水期浮游生物丰度和多样性均低于丰水期，且沿程变化更加不规则，与枯水期梯级水电蓄水大规模改变水流连通性有关。与浮游植物相比，浮游动物群落结构在同一河流的沿程变化和季节变化更加显著，说明所研究河段浮游动物对栖息环境更加敏感。

Study on streamwise variation of plankton community on main stream of Nandujiang River in both flood and draught seasons under influence of cascade reservoirs

In order to investigate the streamwise variation of plankton communities along a river, biological monitoring and studies were carried out along Nandujiang River in Hainan Province of China, which is the unique large scale river in tropic area of China. The monitoring was carried out in the flood season and draught season respectively. For phytoplankton, a total of 151 species belonging to 62 genera were identified with abundance ranging from 2.62×105 cells/L to 26.25×105 cells/L and Shannon-Wiener diversity index ranging from 1.4 to 2.9. For zooplankton, a total of 74 species belonging to 5 genera were identified with abundance ranging from 0.01 ind./L to 157.5 ind./L and Shannon-Wiener diversity index ranging from 1.4 to 2.6. Investigation shows that the streamwise variation of plankton communities on main stream of Nandujiang River is greatly influenced by the cascade hydropower constructions. The density of plankton in reservoirs is usually higher than other parts of the river. Although the seasonal variation of temperature in tropic Rivers is relatively small, water discharges in flood and draught seasons have significant influence on plankton communities. In the draught season, both the biological abundance and the diversity are lower than the flood season and the streamwise variation is more regular, which is related to the water storage in reservoirs and the change of hydraulic connectivity in draught seasons. Compared with phytoplankton, the streamwise and seasonal variations of community structure of zooplankton are more significant, which implies that zooplankton is more sensitive to habitat environment than phytoplankton in the river studied.