宜昌长江南岸岩溶地下水中水生动物群落分布特征及其环境响应

Distribution of aquatic fauna in karstic groundwater and its enviro-nmental response on the south bank of the Yangtze River in Yichang

为探究宜昌长江南岸岩溶区地下水中水生动物群落分布特征及环境响应规律,在2018年7月至8月对宜昌长江南岸15处表层岩溶泉及9处岩溶大泉中水生动物进行采集,同时对地下水理化指标进行测试。共采集到809个动物个体,共有13个亚纲,同时包括多个物种的暗层和非暗层种。结果发现:①不同动物在地下水空间分布上各异,在表层岩溶泉,Copepoda的暗层种和Ostracoda的暗层种大量存在(31.3%,23.7%),Trichoptera和Diptera少量存在(0.4%,2.9%);在岩溶大泉,Copepoda(非暗层种)和Amphipoda大量存在(25.0%,8.3%),Ostracoda的暗层种少量存在(2.2%)。②不同地下水的环境也表现出差异,区内岩溶大泉pH,Na^(+),Ca^(2+),Mg^(2+)等指标的极差(分别为0.64,1.25,34.0,22.1 mg/L)小于表层岩溶泉(分别为2.45,5.68,59.6,33.4 mg/L),表现出更稳定的环境特征。③通过对各环境因子以及不同物种的逐步回归分析得出,表层岩溶泉的主控环境因子为pH,Na^(+),Mg^(2+),岩溶大泉的主控环境因子为pH,SO^(2-)_(4),Mg^(2+);表层岩溶泉的主要代表性生物群落为Ostracoda,Diptera,Turbellaria的暗层物种,岩溶大泉的主要代表性生物群落为Mollusca,Diptera,Decapoda。④通过路径分析发现,生物通过种间相互作用,对环境因子具有直接与间接响应。在表层岩溶泉,Diptera主要通过与Ostracoda的种间关系对Na^(+)和Mg^(2+)起间接响应,另外Ostracoda,Diptera,Turbellaria的暗层种对pH有直接响应;在岩溶大泉,Mollusca主要通过Diptera对pH起间接响应,Diptera通过Decapoda对SO_(4)^(2-)起间接响应,另Mollusca,Diptera,Decapoda对Mg^(2+)直接响应。研究发现生物分布规律是对于环境因子的直接作用和生物之间的间接作用共同响应结果。

To understand the distribution of aquatic fauna in karst groundwater and its environmental response,aquatic fauna and water samples were collected from 15 epikarst springs and 9 large karst springs on the south bank of the Yangtze River in Yichang from July to August 2018.In total,809 individuals were collected,and they belonged to 13 subclasses.We found that:①The spatial distribution of different animals in groundwater was different.Copepoda and Ostracoda stygobionts were abundant in epikarst springs(31.3%,23.7%),Trichoptera and Diptera were less abundant(0.4%,2.9%).Copepoda and Amphipoda were abundant in large springs(25.0%,8.3%),Ostracoda stygobionts were less abundant(2.2%).②The variation range of environmental factors(pH,Na^(+),Ca^(2+),Mg^(2+))in large karst springs(0.64,1.25 mg/L,34.0 mg/L,22.1 mg/L)was narrower than that in epikarst springs(2.45,5.68 mg/L,59.6 mg/L,33.4 mg/L),which indicated a relatively stable condition.③According to the stepwise regression analysis,the main environmental factors of epikarst springs were pH,Na^(+)and Mg^(2+),and the main environmental factors of large karst springs were pH,SO_(4)^(2-)and Mg^(2+).Moreover,the representative biological communities of epikarst springs were Ostracoda,Diptera and dark layer species of Turbellaria,and the representative biological communities of large karst springs were Mollusca,Diptera and Decapoda.④According to the path analysis,Diptera mainly responded indirectly to Na^(+)and Mg^(2+)through Ostracoda,and Ostracoda stygobionts,Diptera and Turbellaria responded directly to pH in epikarst springs.In large karst springs,Mollusca mainly indirectly responded to pH through Diptera,Diptera indirectly responded to SO^(2-)_(4)through Decapoda,and Mollusca,Diptera and Decapoda directly responded to Mg^(2+).The distribution of fauna in groundwater was the result of a direct response to environmental factors and an indirect response between different species.