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

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。

The key environmental factors driving the succession of phytoplankton functional groups in Hongfeng Reservoir, southwest China

Reservoirs are an important water source in many densely populated areas in southwest China.Phytoplankton play an essential role in maintaining the structure and function of reservoir ecosystems.Understanding the succession in phytoplankton communities and the factors driving it are essential for eff ective water quality management in drinking water reservoirs.In this study,water samples were collected monthly at the surface layers from March 2016 to December 2019 in Hongfeng Reservoir,southwest China.The relationship between functional group succession was analyzed based on nonmetric multidimensional scaling analysis(NMDS),redundancy analysis(RDA),succession rate,and other analysis methods.The results showed distinct shifts in the community structure of phytoplankton functional groups within study period.The Cyclotella sp.was dominant in 2016 and 2017,and Pseudanabaena limnetica was the dominant group in 2018 and 2019.It appears that the phytoplankton composition and biomass are closely related to the water temperature and nutrient status in this reservoir.The results clearly showed that the permanganate index(COD_(Mn))was the key factor of dramatic phytoplankton functional group succession,and the change in succession rates was closely caused by total nitrogen concentration(TN).Therefore,the succession pattern and key factors of Hongfeng Reservoir revealed in this study were important guidance for the management of drinking water reservoirs in southwest China.A reasonable limit on exogenous nutrient input should be a priority,especially in high water temperature period.

藏南沉错沉积物水蚤残体组合对环境变化的响应

利用活塞取样器在藏南沉错获取了连续的沉积岩芯,选择顶部的117cm岩芯段进行水蚤(Cladocera)残体分析.根据水蚤的种类、数量和生态习性,从下到上可以将岩芯中水蚤组合划分为5个带:CL0组合(117～101cm)没有发现水蚤;CL1组合(101～77cm,约公元1407～1533年)出现钻孔中的全部9种水蚤,并达到序列中的最高含量,反映了在温暖的沉积环境中有大量的外来冷水注入和有机质输入,湖泊宽浅适宜大型水生植物的生长;CL2组合(77～29cm,约公元1533～1831年)的水蚤数量和种类大大下降,只有为数不多、环境适应性较强的Chydorussphaericus经常存在,说明了当时的沉积环境非常恶劣;CL3组合(29～10cm,约公元1831～1941年)的优势水蚤种类与CL1组合接近,但丰度下降,特别是喜有机碎屑环境的水蚤数量大大降低,反映了环境有利的条件下,流域地表的植被发育仍然较差;CL4组合(10～0cm,约公元1941年到现在)除没有发现浮游型水蚤外,其他7种水蚤均可见到,稳定的湖泊水温使广温型的水蚤种与窄温型的浅水种相比,已经失去竞争优势.该孔水蚤组合反映的环境变化得到其平行孔的介形类组合、环境磁学与相关参数以及硅藻-盐度转换函数研究结果的支持,反映了青藏高原湖泊沉积中的水蚤组合对沉积环境的敏感性和在环境变化研究中的重要意义.