Climate Change and Dissolved Organic Matter in Subarctic Lakes: Relevance to Methylmercury Bioavailability
One of the first steps of methylmercury (MeHg) bioaccumulation, uptake by phytoplankton, is regulated by dissolved organic matter (DOM). Methylmercury binds strongly with DOM, especially high-molecular weight (HMW) compounds containing reduced sulphur; this binding decreases MeHg bioavailability. Cl...
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| Format: | Text |
| Language: | English |
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Scholarship@Western
2019
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| Online Access: | https://ir.lib.uwo.ca/etd/6601 https://ir.lib.uwo.ca/context/etd/article/8927/viewcontent/Final_Thesis_Document__with_revisions_.pdf |
| Summary: | One of the first steps of methylmercury (MeHg) bioaccumulation, uptake by phytoplankton, is regulated by dissolved organic matter (DOM). Methylmercury binds strongly with DOM, especially high-molecular weight (HMW) compounds containing reduced sulphur; this binding decreases MeHg bioavailability. Climate-induced changes were measured at the landscape level using ArcGIS; land-cover changes between 2005-2010 were assessed around lakes in Mackenzie Valley, NWT. The observed changes, a 10% increase in forest-classified area and up to 15% decrease in wetland area, will likely increase delivery of HMW DOM and MeHg to lakes. Partitioning experiments were conducted to examine effects of DOM ligand quality on MeHg uptake by Chlamydomonas reinhardtii algae. In cysteine solution (reduced sulphur DOM), algae took up 89% less MeHg than in EDTA solution and 172% less MeHg than in ‘no DOM’ solution. Together, geospatial and experimental analyses indicate that changing DOM composition will likely cause MeHg bioavailability to decrease in subarctic lakes. |
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