|Abstract Title:||Application of Mercury Stable Isotopes: Temporal Field Assessment of Two Systems of Contrasting Mercury Inputs|
|Presenter Name:||Grace Armstrong|
|Company/Institution:||University of Wisconsin-Madison|
|Session:||Mercury in Freshwater Ecosystems|
|Co-Authors:||Grace Armstrong,Sarah Janssen,Mike Tate,Jacob Ogorek,James Hurley,David Krabbenhoft|
Abstract Information :
In aquatic ecosystems, planktonic uptake of methylmercury (MeHg) is a key step linking mercury (Hg) sources to bioaccumulation and subsequent human and wildlife health concerns. Despite the importance of plankton in aquatic Hg cycling, little information is available regarding temporal shifts in Hg source accumulation as it relates to seasonal patterns or changes in algal community composition. This study examines how Hg and MeHg concentrations and isotopic signatures vary temporally with the algal succession in two inland lakes of contrasting Hg source profiles. The systems examined include two Wisconsin inland freshwater lakes located in urban and suburban watersheds prone to eutrophication and summer anoxia. Mercury sources to these lakes include legacy contamination, watershed inputs, stormwater runoff, and atmospheric deposition. Using recent method advancements, we plan to analyze Hg and MeHg isotopes in plankton collected from the lakes during spring-summer months and under the ice to compare how Hg species cycle and are transformed within ecosystems with contrasting Hg inputs. This presentation will discuss the resulting concentration, isotopic, and algal speciation temporal data from these two systems. Concentration and isotope values in plankton will be compared to fish tissue, sediment, and water measurements. In addition, water quality parameters and plankton species will be compared to isotope data to understand factors influencing Hg isotope changes. Ultimately, this field assessment allows us to gain insight into the reactivity and bioavailability of varying Hg sources, a piece currently missing in our current understanding of Hg biogeochemical cycling.