Water quality of freshwater lakes within the Laurentian Great Lakes region is vulnerable to degradation owing to multiple environmental stressors including climate change, alterations in land use, and the introduction of invasive species. Our research questions were two‐fold: (1) What are the temporal patterns and trends in water quality? (2) Are climate, invasive species and lake morphology associated with changes in water quality? Our study incorporated timeseries data for at least 20 years from 36 lakes in Ontario and Wisconsin sampled between 1976 and 2016. We evaluated patterns in water quality (total phosphorus [TP], total nitrogen, dissolved organic carbon [DOC], and chlorophyll a [Chl a]) using segmented regression analysis which identified significant breakpoints in Chl a and TP in the 1900s to mid‐2000s after which Chl a and TP began to increase, whereas breakpoints in DOC exhibited increasing trends prior to the year 2000 with levels declining afterward. Next, we examined linear trends in water quality and climate (temperature and precipitation) using Sen slope analysis where, generally, over the past 40 years, lake TP and Chl a have significantly declined, whereas DOC has increased. Lastly, we conducted a redundancy analysis (RDA) to identify how climate, lake morphology, and the presence of invasive dreissenid mussels contributed to changes in water quality. The RDA revealed that precipitation, air temperature, and morphology explained 73.1% of the variation in water quality trends for the Great Lakes whereas precipitation, temperature, morphology, and occurrence of mussels explained 45.6% of the variation for smaller inland lakes.

中文翻译：

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过去40年来，劳伦天大湖地区水质变化的驱动因素

由于多种环境压力，包括气候变化，土地利用的变化和入侵物种的引入，劳伦天大湖地区内的淡水湖的水质容易退化。我们的研究问题有两个：（1）水质的时间模式和趋势是什么？（2）气候，入侵物种和湖泊形态是否与水质变化有关？我们的研究纳入了至少20年的时间序列数据，这些数据来自1976年至2016年间安大略省和威斯康星州的36个湖泊。我们评估了水质模式（总磷[TP]，总氮，溶解有机碳[DOC]和叶绿素a [ Chl a ]）使用分段回归分析确定了Chl中的重要断点一个和TP在1900年到2000年代中期之后，叶绿素一和TP开始增加，而DOC断点表现出与水平下降之后在2000年之前增加的趋势。接着，我们检查了在水质和气候（温度和沉淀）的线性趋势使用森斜率分析，其中，一般地，在过去的40年中，湖TP和叶绿素一个显着下降，而DOC增加了。最后，我们进行了冗余分析（RDA），以查明气候，湖泊形态以及侵入性硬皮贻贝的存在如何导致水质变化。RDA显示，降水，气温和形态解释了大湖水质趋势的73.1％，而降水，温度，形态和贻贝的出现解释了较小内陆湖泊的45.6％。