The (Laurentian) Great Lakes region (GLR) of North America contains ∼20% of the world's freshwater by total area. Yet, the water quantity and quality of lakes in this region are threatened by water level fluctuations and excessive algal growth associated with climate warming. To understand the mechanisms that drive these changes, we have established a 900-year history of environmental change using sediments from a small kettle lake, Barry Lake, located within the GLR. To understand how water quantity changed over time, we used stable isotopes of oxygen and carbon in marl to reconstruct effective moisture. Our reconstruction for Barry Lake shows that the Little Ice Age (LIA) was wetter than present, whereas the Medieval Climate Anomaly (MCA) was drier than present. There is considerable spatiotemporal variation in effective moisture across the GLR and northeastern (NE) USA. This variation may reflect changes in the sign of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), which can alter moisture delivery by modifying the strength and position of the polar and subtropical jet streams. To identify changes in water quality, we reconstructed primary production using sedimentary chlorophyll a (Chl-a_(s)) contents and stable isotopes of carbon and nitrogen in organic matter. There was relatively little change until the last 150 years, revealing that shifts in effective moisture did not noticeably influence primary production. Rather, primary production was impacted by anthropogenic pressures such as land use change and associated increases in nutrient delivery. Our research contextualizes recent threats to water quantity and quality in the GLR against a backdrop of environmental change, while also synthesizing hydroclimate records from across this region and the NE USA.

北美的 (Laurentian) 五大湖区 (GLR) 包含世界总面积约 20% 的淡水。然而，该地区湖泊的水量和质量受到水位波动和与气候变暖相关的藻类过度生长的威胁。为了了解驱动这些变化的机制，我们使用位于 GLR 内的一个小水壶湖巴里湖的沉积物建立了 900 年的环境变化历史。为了了解水量如何随时间变化，我们使用泥灰岩中氧和碳的稳定同位素来重建有效水分。我们对巴里湖的重建表明小冰河时代 (LIA) 比现在更潮湿，而中世纪气候异常 (MCA) 比现在更干燥。GLR 和美国东北部 (NE) 的有效水分存在相当大的时空变化。这种变化可能反映了太平洋年代际涛动 (PDO) 和大西洋年代际涛动 (AMO) 符号的变化，这可以通过改变极地和亚热带急流的强度和位置来改变水分输送。为了识别水质的变化，我们使用沉积叶绿素重建了初级生产a (Chl- a _(s) ) 含量和有机质中碳和氮的稳定同位素。直到最近 150 年才发生相对较小的变化，这表明有效水分的变化并未显着影响初级生产。相反，初级生产受到人为压力的影响，例如土地利用变化和相关的养分输送增加。我们的研究在环境变化的背景下将 GLR 的水量和水质最近面临的威胁联系起来，同时还综合了该地区和美国东北部的水文气候记录。