稀土尾矿库复合污染对花背蟾蜍生殖力及种群动态的影响机理

Environmental pollution has become the leading cause of amphibian population declines, while their reproductive capacity plays an important role in the maintenance of population size, so dissection the impact of environmental pollutants to amphibians' reproductive capacity is urgently needed.,However, the influence of rare earth tailings combined pollution on amphibian reproductive capacity as well as population dynamics in natural environment is unclear yet. To address this issue, Bufo raddei, a species widely distributed in the north China, is selected to explore the effect of combined pollution of the rare earth tailings dam on amphibian reproductive capacity as well as population dynamics. A rare earth tailings dam in the Inner Mongolia with higher contamination is chose as the research plot, and Xiaobaihe wetland of Yellow River in Baotou, a relatively unpolluted area is chose as control. Technics such as anatomical structure, age structure assessment, electron microscopy, physicochemical analysis, and DNA gel electrophoresis will be used in this study. The differences on the reproductive capacity and population dynamics of B. raddei between the two areas will be comparatively studied. Through the above research, we will figure out whether the compound pollution around the rare earth tailings dam could have an effect on the reproductive capacity of the B. raddei or not, and demonstrate the possible impact pathways and mechanism.

环境污染已成为导致两栖类种群数量下降的主导因素，两栖类生殖力对其种群数量的稳定有着重要作用。然而，在野外自然环境条件下，稀土金属冶选尾矿库渗漏对其周边区域造成的复合污染如何影响当地两栖类的生殖力和种群动态变化，目前尚不清楚。本项目以花背蟾蜍（Bufo raddei）为研究对象，以内蒙古某稀土金属冶选尾矿库周边受污染的水域湿地和相对无污染的小白河黄河湿地保护区为研究样地。进行野外环境下的实地调查和采样，在实验室内采用组织解剖、年龄结构鉴定、组织电镜观察、理化分析和核酸凝胶电泳等方法，对比分析上述两样地各年龄段的不同性别花背蟾蜍的生殖力及影响因素。结合相关种群动态参数指标，探讨稀土金属选冶尾矿库复合污染对花背蟾蜍生殖力的影响机理。确定其生殖力的改变对花背蟾蜍种群动态变化的影响效应。对当地两栖类种群保护及稀土尾矿库污染防控、监测与评价具有重要意义。

本研究以花背蟾蜍为研究对象，以内蒙古某尾矿库湿地为研究样地。结合野外实地调查的和实验室分析，研究稀土尾矿库复合污染对花背蟾蜍生殖力及种群动态的影响机理。结果发现，尾矿库湿地水体和底泥中的重金属Cu、Cr、Mn、Ni和Zn含量显著高于黄河湿地，尾矿库湿地水体属轻度污染，底泥属重度污染。蟾蜍极易富集Cd、Cu、Zn和Pb。尾矿库湿地污染环境下，花背蟾蜍平均体重、体长和生殖腺指数均显著增大，繁殖能量投入更多。尾矿库湿地蟾蜍卵巢出现组织坏死现象，精巢组织结构规则性变差，精子畸形率增加。肝脏中含铁血黄素沉着过多，组织间隙增大，纤维组织增生破坏了肝组织的正常结构并形成大量结节，伴有局部肝硬化。肾脏中出现了晶体状的玻璃样变性。心肌组织间隙扩大。黄河湿地蟾蜍未发现上述情况。复合污染造成蟾蜍性腺组织的损伤，导致体内性激素水平紊乱，精子活力降低，导致后期受精率和孵化率下降。虽然卵巢指数增大致使尾矿库湿地花背蟾蜍的单只产卵量高于黄河湿地，但总产卵量降低，繁殖能力下降。同时，污染物显著延迟了花背蟾蜍的胚后发育进程。究其原因显示尾矿库湿地复合污染对花背蟾蜍蝌蚪组织的氧化损伤和血细胞DNA损伤程度均显著高于黄河湿地，具有遗传损伤作用。结合蟾蜍的标记与重捕方法，利用单种群确定型模型进行蟾蜍种群生存能力的分析。发现黄河湿地中蟾蜍种群呈增长趋势，而尾矿库湿地中呈衰减趋势。结果显示保护一龄蟾蜍能有效提高当地蟾蜍种群数量。与此同时，尾矿库湿地复合污染导致蟾蜍舌头和腿部肌纤维局部断裂，从而降低了花背蟾蜍的捕食和避敌能力，进一步降低了蟾蜍的生存能力，这也是导致尾矿库等污染场地两栖类种群衰退，生物多样性降低的主要原因之一。本项目研究成果直观的揭示了尾矿库复合污染对两栖类生殖力和种群动态的影响机理。对当地两栖类种群保护及稀土尾矿库污染防控、监测与评价具有重要意义。呼吁当地政府应积极采取措施加强尾矿库区生态环境的治理工作。