A Multi-Element Perspective on Ecosystem Changes in Lake Erie since ~1800

The distribution of major and trace elements in lake sediments can be used to yield insight into past changes in environmental conditions. Such information is essential for detecting modes of regional climate variability and assessing impacts of anthropogenic sources on local watersheds. This study has generated a suite of analytical results of seven major (Al, Ca, Fe, K, Mg, Mn, and Na) and fifteen trace elements (As, Ba, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Se, Sn, Ti, V, and Zn) as measured on 39 samples from a surface sediment core taken from the Sandusky subbasin of Lake Erie. Statistical tools such as hierarchical clustering and principal component analysis (PCA) were employed to better characterize the lake’s ecosystem changes that occurred over the past 210 years. Following a slow eutrophication during European settlement, Lake Erie experienced a period of accelerated eutrophication which eventually resulted in an ecosystem regime transition into a eutrophic lake state in 1950. The lake’s biological productivity has ever since remained fairly high even though a significant reduction in nutrient loading was realized from rigorous abatement programs that began as early as 1969. There is indication that the lake ecosystem was affected by lake-level fluctuations. But the majority of these ecosystem changes as represented by 73% of the elemental variations observed were attributed to inputs from various anthropogenic sources (industrial, municipal, and agricultural wastewaters). This work suggests that the in-lake biogeochemical cycling has played an important role in sustaining the internal loading of bioavailable nutrients and trace elements in this already eutrophic lake today.