Abstract Nelligan C, Jeziorski A, Rühland KM, Paterson AM, Meyer-Jacob C, Smol JP. 2019. A multibasin comparison of historical water quality trends in Lake Manitou, Ontario, a provincially significant lake trout lake. Lake Reserv Manage. 36:243–259. Lake Manitou, on Manitoulin Island (Ontario, Canada), is a two-basin lake that supports a natural lake trout population and currently experiences late-summer hypolimnetic oxygen concentrations below the provincial criterion set to support this sensitive coldwater fish species. However, limited direct monitoring data make it difficult to assess long-term changes in hypolimnetic oxygen concentrations, and to identify what stressors may be responsible for those changes. Dated sediment cores from each basin of Lake Manitou were used to reconstruct end-of-summer volume-weighted hypolimnetic oxygen (VWHO) over the past ∼150 years using assemblages of sedimentary chironomid remains. To assess the influence of nutrients, regional warming, and lake browning, VWHO reconstructions were compared with sedimentary diatom assemblage changes, and spectrally derived trends in both sedimentary chlorophyll a (and its main diagenetic products) and sediment-inferred lakewater total organic carbon. The chironomid-inferred VWHO reconstructions suggest that deepwater oxygen concentrations are currently lower in both basins of Lake Manitou than they were prior to the 20th century (decreasing in the late 1880s coincident with the development of Manitoulin Island by European settlers). In both basins, post-1950 diatom assemblage shifts and whole-lake primary production (sedimentary chlorophyll a) trends suggest that increased nutrient inputs and warming-related changes (i.e., enhanced thermal stability) may be contributing to the current low-oxygen conditions of Lake Manitou. In the west basin, all paleolimnological proxies underwent more pronounced (and often earlier) changes than in the east basin, an observation that suggests more targeted management strategies may be needed to protect Lake Manitou’s coldwater fish population.

中文翻译：

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安大略省马尼图湖历史水质趋势的多流域比较，该湖是省级重要的鳟鱼湖

摘要 Nelligan C、Jeziorski A、Rühland KM、Paterson AM、Meyer-Jacob C、Smol JP。2019. 安大略省马尼图湖历史水质趋势的多流域比较，该湖是省级重要的鳟鱼湖。湖泊保护区管理。36:243-259。马尼图林岛（加拿大安大略省）上的马尼图湖是一个有两个盆地的湖泊，支持天然湖鳟种群，目前夏末的水下氧浓度低于为支持这种敏感的冷水鱼类而设定的省级标准。然而，有限的直接监测数据使得评估水下氧气浓度的长期变化以及确定哪些压力因素可能导致这些变化变得困难。在过去的 150 年里，来自曼尼通湖每个盆地的年代沉积岩心被用来重建夏末体积加权水下氧 (VWHO)，使用沉积摇蚊残骸的组合。为了评估营养物质、区域变暖和湖泊褐变的影响，将 VWHO 重建与沉积硅藻组合变化以及沉积叶绿素 a（及其主要成岩产物）和沉积物推断的湖水总有机碳的光谱衍生趋势进行了比较。摇蚊推断的 VWHO 重建表明，目前马尼图湖两个盆地的深水氧浓度低于 20 世纪之前的水平（在 1880 年代后期下降，与欧洲定居者对马尼图林岛的开发相一致）。在两个盆地中，1950 年后的硅藻组合变化和全湖初级生产（沉积叶绿素 a）趋势表明，养分输入增加和与变暖相关的变化（即热稳定性增强）可能是造成目前曼尼托湖低氧条件的原因。在西部盆地，所有古湖泊学代理都经历了比东部盆地更明显（而且往往更早）的变化，这一观察表明可能需要更有针对性的管理策略来保护曼尼托湖的冷水鱼类种群。