Event
The Department of Earth & Environmental Science
University of Pennsylvania
Invites you to attend a EES Colloquium
Friday, April 11, 2025 - 3:00 PM
"Methane accumulation and degradation in freshwaters: Relevance to climate change and water quality"
One of the largest sources of methane to the atmosphere are freshwater wetlands, ponds and lakes. We have been examining the drivers of methane production and degradation in these systems and we have found that stratification and mixing dynamics play important roles. Mixing enables exchange of methane with the atmosphere, increasing losses but it also increases dissolved oxygen, which increases the degradation of methane to carbon dioxide, also a greenhouse gas, but a less potent one. Nonetheless, lakes are increasingly devoid of dissolved oxygen, due in a large part to warming and longer and stronger stratification. Methane production is both a consequence of oxygen loss but also an important driver due to its lability.
Dr. James Cotner
Professor
College of Biological Sciences
University of Minnesota - Twin Cities
James Cotner has been studying the role of microbes in aquatic systems from freshwater to marine for over 40 years. Microbes are incredibly important to ecosystem processes because of the great magnitude of their biomass and their diverse modes of metabolism (aerobic, anaerobic, sulfate reduction, methanogenesis, iron reduction, sulfide oxidation, metal oxidation, photosynthesis). Because of this diversity of function, bacteria and archaea have significant impacts on the geochemistry of lakes, rivers and oceans. He is particularly interested in how variation in microbial metabolism can affect ecosystem dynamics. Heterotrophic bacteria represent a greater proportion of pelagic biomass and production in oligotrophic than eutrophic systems and their biomass stoichiometry can be incredibly plastic. What does this mean for ecosystem structure and function? Recent work is focused on bacterial and archaeal production and degradation of greenhouse gases (CO2, CH4 and N2O) and release to the atmosphere.