Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $29,806 Total Non-Federal Funds: $49,483
Principal Investigators: Ishi Buffam, Trinity Hamilton
Abstract: We propose to study the link between eutrophication and methane production in Ohio Reservoirs, with a focus on sediment microbial processes. Algal blooms and the associated negative environmental impacts caused by nutrient enrichment have been identified as a leading cause of impairment of surface waters in Ohio. One of the understudied negative consequences of eutrophication is the increased potential for in-lake production and emissions of methane (CH4), a potent greenhouse gas (GHG) with a global warming potential 21 times that of CO2. A recent study found exceptionally high methane emissions in Harsha Lake, a reservoir in southwest Ohio characterized by high nutrient loading rates and persistent summer-time algae blooms. Lab studies have demonstrated that the addition of fresh algal material to lake/reservoir sediments stimulates CH4 production by providing a labile carbon source. These data suggest that increased algal blooms resulting from nutrient pollution may stimulate microbial methane production, contributing to increased emissions. However, it is not known whether this mechanistic relationship translates to the field scale. This is an important question for Ohio water resource management, as Ohio has a large number of reservoirs, many of which suffer from eutrophication due to high nutrient inputs, mainly from agricultural landscapes. The overall objective of this project is to determine the relationship between the occurrence of algal blooms and CH4 production from reservoir sediments at two spatial scales, with the following aims: Aim #1: Determine the relationship between organic matter quantity and quality, CH4 production and methanogen communities in sediments from Harsha Lake, over a within-reservoir spatial gradient in nutrient and algal organic matter loading. Aim #2: Determine the relationship between organic matter quantity and quality, CH4 production and methanogen communities in sediments from 18 Ohio (and nearby) reservoirs, varying across a gradient of watershed land-use/land-cover and trophic status. We will address these aims by determining sediment CH4 production, methanogen abundance and microbial community structure, and sediment organic matter characteristics (including C/N, stable isotopes of C and N, and lipid content) along a transect of 15 sites in Harsha Lake, and at two locations in each of 18 reservoirs throughout the state. This study will fill an important knowledge gap related to Ohio Water Resources, getting at the link between eutrophication and GHG emissions on a within reservoir-scale as well as across land-use gradients throughout Ohio. The study will provide needed information on the GHG-related co-benefits of nutrient reduction to reservoirs, and will allow for a more informed valuation of the impact of nutrient loads, information which may ultimately contribute to a reduction in nutrient pollution. The research will also have a broader relevance since globally, reservoirs are estimated to be responsible for 5-20% of the annual anthropogenic emissions of CH4. The project will support one MS student thesis project and an undergraduate research assistant, under the guidance of two early-career faculty members at the University of Cincinnati. The information generated will also be communicated directly to the Army Corps of Engineers who manage Harsha Lake and other reservoirs in the region.