Contrasting Nearshore and Offshore Responses to the Tributary Inputs of Carbon and Sulfur into Lake Erie Fasong Yuan1, Bernhard Mayer2, Laodong Guo3 1Cleveland State University, Cleveland, Ohio, USA; 2University of Calgary, Calgary, Alberta, Canada; 3University of Wisconsin, Milwaukee, Wisconsin, USA [ABSTRACT] To better understand the geochemical and ecological response to tributary inputs SAMPLING SITES (12/9/2016 ~ 9/15/2017): into Lake Erie, water samples from offshores, nearshores, and major rivers in Michigan (Detroit), Ohio (Maumee, Sandusky, Portage, Cuyahoga, Grand, and Conneaut Creek), Pennsylvania . (Presque Isle) and New York (Niagara) were collected for the measurements of concentrations of Cl, SO4, dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC), oxygen and hydrogen isotopic ratios of water (d18O and d2H), and sulfur and oxygen isotopic ratios of sulfate 34 18 (d SSO4 and d OSO4). We found that concentrations of Cl and SO4 in the nearshore environments were greater than those in the offshore sampling sites, but less than those of the tributaries. In 18 2 34 18 contrast, values of d O and d H and d SSO4 and d OSO4 in the nearshore environments were lower than those in the offshore sampling sites, but higher than those in the tributaries, showing the influence of water and solute inputs from Lake Huron. Lake Erie exhibited eastward trends of 34 18 increasing Cl and decreasing d SSO4 values and some fluctuations in SO4 and d OSO4. The 18 lowest levels of SO4 found in the offshore sites coincided with the greatest values of d OSO4, suggesting that sulfur transformations (e.g., bacterial sulfate reduction) were active in the hypoxic waters of central Lake Erie. Furthermore, we found that concentrations of DOC and DIC in the tributaries were greater than those in the nearshore and offshore sampling sites. Despite a generally eastward decrease in DOC and DIC across the lake, values of DOC and DIC were 5- 10% greater in the outflowing Niagara River at Fort Erie (New York) than in the inflowing Detroit River (Michigan). This suggests that western Lake Erie subject to frequent algal blooms and hypoxic events is a source for carbon, contributing to DOC and DIC export to Lake Ontario. Fig. 2 Chemical and isotopic compositions of Lake Erie. SL: Sterling State Park (MI); CI: Catawba Island (OH); VM: Vermilion (OH), EW: Edgewater Park (West Cleveland, OH); EF: East Fifth Street Marina (East Cleveland, OH); ML: Mentor- on-the-lake (OH); GL: Geneva-on- the-lake (OH); PI: Presque Isle (PA); DK: Dunkirk (NY); FE: Fort Erie (NY). CB: offshore waters from the Central Basin. Note that most of the samples were collected between May and September 2017. Although only CB samples were taken from open water in the lake, samples from CI and FE showed some characteristics (low salinity and high isotopic values) of open waters. If you are interested and want to learn more about this project, please do not hesitate to contact Dr. Yuan via email: [email protected] Fig. 1 Chemical and isotopic compositions of tributaries into Lake Erie. DR: Detroit River; MR: Maumee River; SR: Sandusky River; PR: Portage River; CR: Cuyahoga River; GR: Grand River; CC: Conneaut Creek. H13K-1894 AGU Fall Meeting December 10-14, 2018 Washington DC .