Age models and bulk organic isotope geochemistry from Lake Superior sediment cores

Anthropogenic climate change has the potential to alter many facets of Earth's freshwater resources, especially lacustrine ecosystems. The effects of anthropogenic changes in Lake Superior, which is Earth's largest freshwater lake by area, are not well documented (spatially or temporally) and predicted future states in response to climate change vary. Here we show that Lake Superior experienced a slow, steady increase in production throughout the Holocene using (paleo)productivity proxies in lacustrine sediments to reconstruct past changes in primary production. Furthermore, data from the last century indicate a rapid increase in primary production, which we attribute to increasing surface water temperatures and longer seasonal stratification related to longer ice-free periods in Lake Superior due to anthropogenic climate warming. These observations demonstrate that anthropogenic effects have become a prominent influence on one of Earth's largest, most pristine lacustrine ecosystems.人为气候变化可能会改变地球淡水资源的诸多方面，尤其是湖泊生态系统（lacustrine ecosystem）。苏必利尔湖作为全球面积最大的淡水湖，目前针对其受人为活动影响的相关研究无论在空间还是时间维度上均缺乏充分记录，且不同研究对其响应气候变化的未来状态预测亦存在分歧。本研究通过分析湖相沉积物（lacustrine sediments）中的（古）生产力代用指标（(paleo)productivity proxies），重建了过去的初级生产力变化，结果显示苏必利尔湖在全新世（Holocene）期间的生产力始终呈缓慢且稳定的增长态势。此外，近一个世纪的观测数据显示该湖的初级生产力出现快速增长，我们将这一现象归因于表层水温升高与季节性水体分层持续时间延长——这两者均与人为气候变暖导致的苏必利尔湖无冰期延长密切相关。上述观测结果表明，人为影响已成为全球面积最大且保存最为完好的原始湖泊生态系统之一的显著驱动因素。