Collaborative Research: Holocene biogeochemical evolution of Earth's largest lake system

人类正在对五大湖造成的影响是众所周知的。这些影响包括气候变化、污染、养分负荷、发展和入侵物种。然而，五大湖自上一次冰河时代末期形成以来，由于自然气候变化事件而在这些人为影响之前的演变情况却鲜为人知。这项研究将是第一批调查五大湖元素地球化学循环的研究之一。这些旋回反映了地质时期的生物活动，如生产力和含氧量。这项工作将涉及从苏必利尔湖、休伦湖和伊利湖收集沉积物岩芯。将在这些沉积物中测量各种元素和同位素浓度，以评估过去的湖泊状况。该项目将同时支持密歇根州立大学和中央密歇根大学的研究生和本科生。该团队将与密歇根K-12学校和当地社区合作，与密歇根海洋基金会和休伦湖上的雷湾国家海洋保护区等知名组织合作。该项目将从6个五大湖地点--苏必利尔湖、休伦湖和伊利湖各收集2个--收集活塞芯沉积物，以调查当地和地区的全新世生物地球化学循环及其对持续的人为扰动和气候变化的洞察。我们的选址之所以成为目标，是因为它们在营养条件和水中的停留时间上存在梯度，包括现代研究最充分和最具吸引力的地点之一--休伦湖目前天然缺氧的中岛沉坑，伊利湖季节性缺氧的中部和东部盆地，以及苏必利尔湖的西部和东部系泊地点。具体目标包括：(A)在整个全新世，自然气候变化如何影响生产力和生物必需微量元素的行为？(B)整个全新世，自然气候变化对氧化还原条件有何影响？(C)湖内和湖间的异质性是否反映了更大的区域环境反馈？(D)成岩作用和其他局部变化在每个地点的代理动态中起什么作用？这些问题将使用地球化学指标来解决，包括汞同位素、营养物质浓度及其同位素，以及氧化还原敏感和生物活性的痕量元素。这一奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The ongoing human impacts on the Great Lakes are well known. These impacts include climate change, pollution, nutrient loading, development, and invasive species. However, the evolution of the Great Lakes before these human impacts due to natural climate change events since their formation at the end of the last ice age is less understood. This study will be among the first to investigate elemental geochemical cycles in the Great Lakes. These cycles reflect biologic activity such as productivity and oxygen contents over geologic time. This work will involve collecting sediment cores from Lakes Superior, Huron, and Erie. A variety of element and isotope concentrations will be measured in these sediments to assess past lake conditions. This project will support graduate and undergraduate students at both Michigan State University and Central Michigan University as well. The team will conduct outreach to Michigan K-12 schools and local communities working with established organization like Michigan Sea Grant and the Thunder Bay National Marine Sanctuary on Lake Huron.This project will collect piston cores of sediment from 6 Great Lakes sites— 2 from each of Lake’s Superior, Huron, and Erie—to investigate the local and regional Holocene biogeochemical cycling and its insights into ongoing anthropogenic perturbations and climate change. Our sites are targeted because they span a gradient in trophic conditions and water residence times and include among the best studied and highest interest sites in the modern—the currently naturally hypoxic Middle Island Sinkhole of Lake Huron, the seasonally hypoxic Central and Eastern Basins of Lake Erie, and the Western and Eastern Mooring sites of Lake Superior. Specific objectives include: (A) How has natural climate change impacted productivity and the behavior of bioessential trace elements through the Holocene? (B) How has natural climate change impacted redox conditions through the Holocene? (C) Do intra and inter-lake heterogeneity reflect larger regional environmental feedbacks? (D) What role do diagenesis and other local variations play in proxy dynamics at each site? These questions will be addressed using geochemical proxies, including mercury isotopes, nutrients concentrations and their isotopes, and redox-sensitive and biologically active trace elements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.