Coastal wetlands are essential to the ecosystem health of the Laurentian Great Lakes (North America) watershed. Multiple anthropogenic stressors have been impacting coastal wetlands since European settlement ca. 1850, and remain a concern for wetland health as watershed development intensifies. We used paleolimnological techniques to explore temporal ecosystem dynamics over the last ~ 100 years in two highly degraded Lake Ontario coastal wetlands located in southern Ontario, Canada, using Cladocera (Branchiopoda, Crustacea) subfossil remains as paleoecological indicators. In Cootes Paradise Marsh (Hamilton, Ontario), cladoceran assemblage changes exhibited a shift in dominance from Chydorus to Bosmina, at the turn of the twentieth century. That shift likely reflected the loss of aquatic macrophytes, and corresponds to the postulated timing of the arrival of invasive carp. Despite recent remediation efforts, including attempts to exclude carp from the wetland, little ecological recovery is evident from the subfossil Cladocera assemblage. No Daphnia remains were observed in our sediment core from Cootes Paradise, in contrast to previous studies on extant zooplankton communities, which reported a large Daphnia population in the west end of the marsh in the 1940s. This could indicate that our sediment core recorded ecological changes solely in the east end of Cootes Paradise Marsh. In Jordan Harbour (Lincoln, Ontario), Bosmina were dominant throughout the sediment record, and increases in littoral cladocerans were observed in the most recent sediments, in particular the appearance of periphytic Pleuroxus taxa after ~ 2008. This suggests that some recovery of aquatic macrophyte communities occurred in response to shoreline remediation efforts. Bosmina size structure exhibited only minimal changes in both wetlands, despite known large changes in historic fish community structure. Overall, our study provides perspectives on the benefits and limitations of paleolimnology for documenting ecological change in the Laurentian Great Lakes coastal wetlands.

沿海湿地对劳伦式大湖（北美）流域的生态系统健康至关重要。自欧洲定居以来，多种人为压力源一直在影响沿海湿地。1850年，随着流域发展的加剧，湿地健康仍然受到关注。我们使用古湖泊学技术在加拿大安大略省南部的两个高度退化的安大略湖沿海湿地中探索近100年的时间生态系统动态，使用克拉多菌（Blachiopoda，Crustacea）亚化石作为古生态指标。在库特斯天堂沼泽（安大略省汉密尔顿）中，锁骨的组合变化显示了从虎尾草到波斯尼亚的主导地位转移，在20世纪初。这种变化可能反映了水生植物的损失，并且与入侵鲤鱼到达的假定时机相对应。尽管最近采取了补救措施，包括试图将鲤鱼排除在湿地之外，但从化石克拉科德拉组合中几乎看不到任何生态恢复。没有水蚤我们从Cootes天堂沉积物岩心观察遗体，而相比之下，在现存的浮游动物群落以往的研究，报告大水蚤在沼泽的20世纪40年代的伦敦西区的人口。这可能表明我们的沉积物核心仅在库克斯天堂沼泽东端记录了生态变化。在约旦港（林肯，安大略省），象鼻在整个沉积物中记录都是主要的，在最近的沉积物中观察到沿海的枝角类动物的增加，特别是在〜2008年之后出现的水生Pleuroxus分类群的出现。这表明响应海岸线修复工作，水生大型植物群落有所恢复。尽管已知的历史鱼类群落结构发生了巨大变化，但在两个湿地中，波斯尼亚的大小结构仅表现出最小的变化。总体而言，我们的研究提供了关于古脂学在记录劳伦式大湖沿岸湿地生态变化中的利弊的观点。