LGL biogeochemical cycling

By collecting piston cores from Lakes Superior, Huron, and Erie, we propose to reconstruct LGL biogeochemical evolution over the Holocene. These 3 lakes are targeted because they span a range of trophic and redox conditions, display 2 orders of magnitude of water residence time and have evidence for past changes. We specifically aim to assess the following: Research Questions: Q1. How has natural climate change impacted productivity and the availability of bio-essential TEs through the Holocene? Alongside classic C, N, and P approaches, our spearhead proxies for this task will be barium (Ba), nickel (Ni), and cadmium (Cd) systematics. Q2. How has natural climate change impacted LGL redox conditions through the Holocene? Our spearhead proxy for this task will be iron (Fe), molybdenum (Mo), uranium (U), vanadium (V) and other redox-sensitive TE systematics. Q3. Do intra and inter-lake heterogeneity of Q1-Q2 reflect larger regional environmental feedbacks? We will apply Hg isotopes to constrain TE sources (atmosphere, watersheds), lake clarity, and ice cover. Q4. What role do diagenesis and other local variations play in proxy dynamics at each site? We propose a control approach (2 sites/Lake) in order to recognize local versus broader variations. Broader Impacts: B1. Shared resources and synergies. The cores will be archived at the Continental Scientific Drilling core facility at the University of Minnesota for future research, included already identified synergies in Lake Huron. B2. Community Outreach. We will communicate our results within the framework of LGL natural history at already established and popular outreach events at MSU’s Science Museum, via Michigan Sea Grant, and at the Thunder Bay National Marine Sanctuary. B3. Student Education and Training. Graduate and undergraduate students from both MSU and CMU will be involved in all aspects of the proposed research, including the cruise and sampling party. B4. Policy. We will annually attend the International Association of Great Lakes Research and the summit meeting for the NOAA’s Center for Integrative Great Lakes Research to provide policy perspectives on modern hypoxia management based on our novel records of natural hypoxia.