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Effects of algal-derived carbon on sediment methane production in a eutrophic Ohio reservoir
Citation:
Berberich, M., J. Beaulieu, I. Buffam, S. Waldo, AND T. Hamilton. Effects of algal-derived carbon on sediment methane production in a eutrophic Ohio reservoir. Presented at AGU Fall Meeting, San Francisco, CA, December 12 - 16, 2016.
Impact/Purpose:
To inform the public
Description:
Nutrient loading is known to have adverse consequences for aquatic ecosystems, particularly in the form of algal blooms that may result. These blooms pose problems for humans and wildlife, including harmful toxin release, aquatic hypoxia and increased costs for water treatment. Another potential disservice resulting from algal blooms is the enhanced production of methane (CH4), a potent greenhouse gas, in aquatic sediments. Laboratory experiments have shown that algal biomass additions to sediment cores increase rates of CH4 production, but it is unclear whether or not this effect occurs at the ecosystem scale. The goal of this research was to explore the link between algal-derived carbon and methane production in the sediment of a eutrophic reservoir located in southwest Ohio, using a sampling design that capitalized on spatial and temporal gradients in autochthonous carbon input to sediments. Specifically, we aimed to determine if the within-reservoir gradient of sediment algal-derived organic matter and sediment CH4 production rates correlate. This was done by retrieving sediment cores from 15 sites within the reservoir along a known gradient of methane emission rates, at two separate time points in 2016: late spring before the sediments had received large amounts of algal input and mid-summer after algal blooms had been prevalent in the reservoir. Potential CH4 production rates, sediment organic matter source, and microbial community composition were characterized at each of the sites during both sampling periods. Sediment organic matter was characterized by source using a combination of C/N ratios, C and N stable isotopes, and excitation emission matrix spectroscopy (EEMs). Potential CH4 production rates were highest from sediments near the reservoir inlet, which corresponds to the highest rates of emission from the water surface, and to the highest rates of inputs of new algal material based on sedimentation rates measured at a subset of locations. Results from this study will contribute to a process-based understanding of factors influencing methane production in open water ecosystems.
