Sulfur Cycling in Low Nutrient Lake Environments (2021-04-02)

Friday, April 2, 2021; 3:00 p.m. Remote via Zoom; Janna Quick, Master's Student, Department of Chemistry & Biochemistry, University of Minnesota Duluth; Research Advisor: Dr. Kathryn SchreinerThe sulfur cycle is comprised of both oxidative and reductive processes,and sulfur transforms through a multitude of different valence states.Sulfate is the dominate form of sulfur in freshwater lake environmentsand it is sourced from rock weathering, fossil fuel burning, wastewaterrunoff, and atmospheric deposition. Low nutrient lakes, such as LakeSuperior, demonstrate a low concentration of sulfate. Theseenvironments can be considered a proxy for the Archaean oceanbecause they reflect the low sulfate concentration marine waters oncehad prior to rising oxygen levels in the atmosphere. Due to the low concentration of sulfate in low nutrient lakes, it can bedifficult to quantify the sulfate species that participate in sulfur cycling inthe water column. Researchers have had more success estimating ratesof cycling in the sediment, and recent studies have suggested thatmicrobial mineralization of organic sulfur species contributes to a flux ofsulfate from the sediment to the water column, specifically in low sulfateenvironments. These organic sulfur species are comprised of estersulfates and sulfur containing amino acids. The details and implicationsof characterizing cryptic sulfur cycling in low nutrient lake environmentswill be discussed