广西武鸣盆地岩溶泉口浮游生物群落对水环境变化的响应

Responses of plankton community to water environment changes in karst springs in Wuming Basin,Guangxi Province

近年来我国西南岩溶地区一些岩溶泉出现水生生态系统由草型向藻型转变的问题,但水化学监测却显示泉水水质依旧良好.岩溶泉的水质变化与水生生态系统退化不同步,故探寻岩溶泉水环境的变化以及浮游生物群落的响应,对全面掌握和客观评价泉水的健康状况具有重要意义.于2016年7月、2020年7月两个时期对广西武鸣盆地内4个岩溶泉进行了浮游生物调查和水环境监测.结果显示,4年后浮游生物检出种类和数量增加.浮游植物快速繁殖,总丰度由1.71×10^(5) cells/L上升至79.92×10^(5) cells/L,蓝藻门或绿藻门比例上升;浮游动物总丰度由264.28 ind./L降至137.25 ind./L,大型甲壳类浮游动物密度减少,部分泉口轮虫类密度增加.同时,优势种转变为更适应于富营养化环境的耐污种,或耐污种种类和数量上升.浮游生物的多样性与水体营养水平并未完全吻合.理化指标的水质评价结果显示,4个泉的水质仍属于Ⅰ类或Ⅱ类,但综合营养状态指数显示营养状态均向富营养化方向发展,大部分泉基本已处于中富营养水平.冗余分析结果显示,水温、pH、亚硝态氮、总磷、硝态氮浓度是影响岩溶泉浮游植物群落结构的主要环境因子.浮游动物群落结构与水温、亚硝态氮、氨氮和叶绿素a浓度显著相关.两个时期浮游生物对主要水环境因子的变化有了一定的响应.建议岩溶泉的水质评价依据理化指标的同时还应关注生物指标,多个指标的相互验证才能更全面的反映水体健康状况.同时,为使泉口以及区域地下水资源的可持续开发利用,建议对重要泉口划分泉域保护区,控制泉口污染物的输入,合理开发和管理地下水资源,对已转变的水生生态系统可考虑尽快进行生态修复.

The shift from a clear macrophyte-dominated state to a turbid algal-dominated state has been occurred in some karst springs of Southwest China in recent years,but hydrochemical monitoring still reveal good conditions.The trend of water quality in karst springs is not synchronous with the degradation of aquatic ecosystem.To understand comprehensively and evaluate objectively the health of the spring water,we discussed how plankton community responds to water environment.Plankton investigation and physicochemical parameters monitoring have been conducted at four karst springs of the Wuming Basin,Guangxi province,in July 2016 and July 2020,respectively.The results showed that the number of species and density of plankton detected have increased 4 years later.Reproduced rapidly,the phytoplankton abundance of those all springs increased from 1.71×10^(5) cells/L to 79.92×10^(5) cells/L.And the total abundance of zooplankton decreased from 264.28 ind./L to 137.25 ind./L.The proportion of Cyanophyta or Chlorophyta in each spring increased,while density of some large crustacean's species reduced.And density of Rotifer has increased in some springs.Furthermore,some dominant species have converted to the species typically found in the eutrophicated environment.The number of species tolerant to pollution has increased also.However,the plankton hiodiversity does not fully coincide with trophic levels.The water quality based on physicochemical parameters were ranked as either category Ⅰ or Ⅱ,while the comprehensive trophic state index of all springs has raised gradually.And most springs has been polluted in middle-heavy eutrophication level.Result from Redundancy analysis showed that phytoplankton communities were significantly related to water temperature(WT),pH,nitrite nitrogen(NO_(2)^(-)-N),total phosphorus and nitrate nitrogen.The main environmental factors affecting the zooplankton community structure were WT,NO_(2)^(-)-N,ammonia nitrogen and chlorophyll-a.The plankton has responded to changes of the major water environmental factors.We suggest that water quality evaluation of karst spring should be combined with the physicochemical parameters and biological indicators.Multiple indexes could more comprehensively reflect the health state of water.Lastly,in order to develop groundwater sustainably,it is suggested to divide spring protection areas for important springs,take measures to prevent springs from being polluted,and reasonably manage and develop groundwater resources.Ecological restoration should be conducted for the damaged aquatic ecosystem as soon as possible.