Silver mining has a long history in Cobalt (Ontario, Canada), and it has left a complex environmental legacy where many lakes are contaminated with arsenic-rich mine tailings. In this exploratory survey, we examined subfossil Cladocera remains in the surface sediments of 22 lakes in the abandoned mining region to assess which environmental variables may be influencing the recent assemblage structure. Further, using a “top-bottom” paleolimnological approach, we compared the recent (top) and older (bottom) assemblages from a subset of 16 lakes to determine how cladoceran composition has changed in these lakes. Our regional survey suggests that the cladoceran assemblages in the Cobalt area are primarily structured by differences in lake depth, while site-specific limnological characteristics, including those related to past mining activities, may have limited roles in shaping the recent cladoceran compositions. The top-bottom paleolimnological analysis suggests that the cladoceran assemblages have changed in most lakes around Cobalt, however the magnitude and nature of changes varied across the study sites. As with most regional biological surveys, the responses to historical mining activities were not uniform across all sites, which further emphasizes the importance of considering site-specific limnological characteristics and multiple environmental stressors when assessing the impacts of mining pollution.

在钴（加拿大安大略省）的银矿开采历史悠久，它留下了复杂的环境遗产，许多湖泊都被富含砷的矿山尾矿污染。在这项探索性调查中，我们检查了废弃矿区22个湖泊表层沉积物中的Cladocera亚化石残留，以评估哪些环境变量可能会影响最近的组合结构。此外，我们使用“顶部-底部”古湖泊学方法，比较了16个湖泊的子集中最近（顶部）和较旧（底部）的组合，以确定这些湖泊中锁骨的组成如何变化。我们的区域调查表明，钴地区的锁骨类组合主要是由湖深的差异构成的，而特定地点的岩相学特征（包括与过去的采矿活动有关的岩理学特征）在塑造最近的clacerceran组合物中的作用可能有限。从上至下的古湖泊学分析表明，在钴周围的大多数湖泊中，锁骨的组合已经发生了变化，但是，变化的幅度和性质在研究地点之间有所不同。与大多数区域生物学调查一样，在所有场所对历史采矿活动的反应也不尽相同，这进一步强调了在评估采矿污染的影响时考虑特定场所的岩性特征和多种环境压力的重要性。