Long-term data are required to quantify the impacts of historic industrial pollution and subsequent remedial action on the nearshore benthic community in the St. Lawrence River Area of Concern at Cornwall, Ontario. Specifically, high-quality temporal records are needed to understand changes in benthic invertebrate assemblages in response to multiple possible drivers including industrial pollution, environmental heterogeneity, and climate warming. We compare long-term records of subfossil chironomid assemblages and geochemical variables among sediment cores from two Cornwall sites with differing pollution histories and a minimally disturbed downstream reference site. Chironomids were functionally absent from the Cornwall sediment cores when mercury and zinc concentrations were elevated. As metal concentrations decreased in more recent sediment intervals, chironomid abundance and the relative abundance of pollution-sensitive taxa increased. Recently deposited sediment in all three sediment cores display increased relative abundance of warm-water, macrophyte-associated taxa. We conclude that these temporal changes in chironomid assemblages provide evidence for ecological recovery for both of the impacted sites, consistent with the objectives of the current management strategy. These findings advance our understanding of industrial impacts on fluvial chironomid ecology, directly inform local management strategies, and further develop the application of chironomids as bioindicators for contaminated sediments.

需要长期数据来量化历史工业污染的影响以及随后的补救行动对安大略省康沃尔郡圣劳伦斯河关注区近岸海底生物群落的影响。具体来说，需要高质量的时间记录来了解底栖无脊椎动物群落的变化，以应对多种可能的驱动因素，包括工业污染、环境异质性和气候变暖。我们比较了来自两个具有不同污染历史的康沃尔遗址和一个受干扰最小的下游参考地点的沉积岩芯中亚化石摇蚊组合和地球化学变量的长期记录。当汞和锌浓度升高时，康沃尔沉积岩芯中的摇蚊在功能上不存在。随着最近沉积区间的金属浓度下降，摇蚊丰度和污染敏感类群的相对丰度增加。最近在所有三个沉积物岩芯中沉积的沉积物显示，与温水、大型植物相关的类群的相对丰度有所增加。我们的结论是，摇蚊组合的这些时间变化为两个受影响地点的生态恢复提供了证据，这与当前管理策略的目标一致。这些发现增进了我们对工业对河流摇蚊生态影响的理解，直接为当地管理策略提供信息，并进一步开发摇蚊作为污染沉积物生物指示剂的应用。