Collaborative Research: Unraveling the Dynamics of Microbial Mercury Methylation in Two Meromictic Lakes in Central New York, USA

Suny College Of Environmental Science And Forestry, Syracuse NY

Investigators

Abstract

Mercury is a widespread pollutant and its impacts on human and ecosystem health have spurred domestic and international policies and regulations that aim to limit its release and transport. Anthropogenic mercury contamination results from emissions to the atmosphere and releases to land and water. Aquatic ecosystems are the ultimate recipients of atmospheric and terrestrial mercury. They play a central role in the transformation of mercury to its most biologically accumulative form, methyl mercury—a known neurotoxin affecting brain development and reproductive, immune, and cardiovascular systems in humans and wildlife. Therefore, a critical need is to advance the understanding of factors influencing in-situ production of methylmercury. This project will improve the prediction of methylmercury concentrations in lakes and other inland systems. It will distinguish the effects of chemical interactions from the roles of microbial transformations in controlling methylmercury production and accumulation. The study will be conducted in Central New York, at two nearby lakes with distinct vertical chemical and biological structure: Glacier Lake and Fayetteville Green Lake. The proposed work will provide training opportunities for undergraduate and graduate students from diverse and non-traditional backgrounds. Scientific hand-on exploration will engage K-12 students from different age groups, culture, ethnical and racial identity. The results of this study will be disseminated through conferences and scientific publications. The principal investigators will impart the scientific findings to the broader scientific and policy community through policy briefs and short presentations at the meetings of the Conference of the Parties, expert working groups, and the intersessional consultations of the Minamata Convention on Mercury. Methylation of mercury is the critical process linking the atmospheric mercury emissions, deposition to the landscape, and mercury bioavailability in aquatic ecosystems. Methylmercury poses a risk to human and wildlife health and may require management interventions. This project will investigate the dynamics of mercury in the water column of two proximal meromictic lakes with well-defined redox profiles and a transitional chemocline of over a meter. The clear natural geochemical gradient combined with discrete thin-layer sampling will enable the distinction between geochemical and biological regulators of mercury methylation in the lakes. The team will perform fluorescence and molecular characterization of dissolved organic matter compounds that sequester mercury. Depth profiles of major elements (S, C, N), speciation of mercury, determination of dissolved organic material and its complexation with mercury, and dissolved low-molecular weight acids and alcohols will be integrated to evaluate factors driving in-situ mercury availability and methylmercury production. In addition, molecular analysis will be used to determine the nature, taxonomic identity, and spatial position of organisms capable of methylating mercury. Genome-centric metagenomics will enable the linkage of mercury methylation to other metabolic traits and provide a scaffold for metatranscriptomics, which will reveal the physiological conditions under which microorganisms methylate mercury absent substrate limitation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.