Biological and physicochemical mechanisms affecting phosphorus and arsenic efflux from prairie reservoir sediment, Buffalo Pound Lake, SK, Canada.
D'Silva, Lawrence Peter 1991-
Eutrophication and algal blooms pose environmental and economical issues in freshwater lakes globally. Algal bloom development is primarily attributed to phosphorus (P), which can be released from lake bottom sediments under certain environmental conditions. Simultaneous to P release, arsenic (As), which is a geochemical P analogue, can be mobilized from sediments and exert toxicity in aquatic organisms. Recent studies within the Canadian prairies have focused on concerns regarding water scarcity and the increased development of algal blooms. However, lake sediments within the Canadian prairies, which are susceptible to P and As mobilization, have received little attention. Using a regionally important freshwater lake (Buffalo Pound Lake, SK, Canada), the goal of this study was to identify environmental mechanisms and geochemistry that influenced P and As mobilization from Canadian prairie lake sediment. Laboratory sediment core incubation experiments demonstrated that warm temperatures (19°C) had the greatest influence on P mobilization from sediment, followed by high pH (pH=9.2), and then low dissolved oxygen (DO) concentrations (<1 mg O2 L-1). High pH had the greatest influence on As mobilization from sediment, followed by warm temperatures, and then low DO concentration. The content of total P, relatively labile P fractions, and total As in sediment were not significantly different among sites. However, concentrations of aluminum (Al) and iron (Fe), common P and As sorbents in sediment, were significant different among sites. In sediment core incubations, the site that displayed less P and As mobilization under anoxic conditions also contained greater concentrations of Al in sediment. Redox-insensitive Al likely mitigated P and As mobilization under anoxic conditions, as evident by decreased P and As mobilization. Phosphorus and As were also mobilized from sediment in situ during ephemeral periods of bottom water stratification and suboxia. Although these conditions are known to facilitate P release in Fe-poor, polymictic lakes, this paradigm appears to also apply to As mobilization. Similar to the laboratory results, less P and As were mobilized in situ from sediment containing greater Al content. Overall, results demonstrated that, in addition to the above environmental variables, sediment geochemistry has a major influence on P and As mobilization from sediment in this Canadian prairie lake. Overall, it is important to determine concentrations of geochemical sorbents (i.e., Fe and Al) when studying P and As mobilization in shallow freshwater lakes globally.
DegreeMaster of Science (M.Sc.)
SupervisorLiber, Karsten; Doig, Lorne E
CommitteeBaulch, Helen M; Giesy, John P; McBeth, Joyce M
Copyright DateJanuary 2017
Buffalo Pound Lake