Master of Science (MSc)
Faculty of Science
As salinity increases the geochemical speciation of Cu is altered as a result of organic/inorganic complexation/competition. Such salinity changes may further challenge the osmoregulatory capabilities of euryhaline organisms. This chemical-biological interaction complicates the understanding of the impacts of Cu in estuarine waters. Dissolved organic matter (DOM) has been widely established to be an important modifier of Cu toxicity in freshwaters however its effectiveness in modulating Cu toxicity across the range of salinities that occur in estuarine conditions has not been studied in a systematic manner. Site to site differences in DOM quality with respect to the potential for toxicity mitigation are also not well understood. The purpose of this study was to examine the mitigating effects of salinity and DOM on acute/chronic Cu toxicity to mysids (Americamysis bahia) using EPA-standardized 96h and 7d toxicity tests. An array of Cu concentrations (0 – 800 µg/L) were tested in duplicate (acute) and quadruplicate (7d) exposure over a wide range of salinities (5 – 40 ppt) with DOM from 4 different sources (at 0-4 mg C/L). A protective effect of salinity on acute Cu toxicity was observed however the organism was found to be more sensitive to Cu at salinity extremes. A protective effect of salinity was observed only for biomass and minimal effect was observed for other chronic end-points. The presence of DOC resulted in a protective effect to A. bahia against Cu toxicity at both 15 and 25 ppt. This protection was variable among sources, with some sources imparting greater protective effects than others and this difference could not be explained by optical characteristics of DOM. There was little variation among sources and resultant toxicity suggesting that DOM quality may not be as important in predicting Cu toxicity in estuarine environments. Overall, the results of this study suggest that toxicity prediction in estuarine environments may not only be dependent on Cu geochemistry but the physiological capabilities of the organisms. Future estuarine toxicity prediction models for estuarine systems therefore need to account for the variability in physiology of estuarine organisms to develop models that accurately predict Cu toxicity. This project helps towards improving the understanding of Cu toxicity in estuarine systems and contributes data towards development of toxicity prediction models which may contribute to guidelines/criteria development for protection of aquatic biota.
Nasir, Rabia, "Effects of Salinity and Dissolved Organic Matter on Cu Toxicity to Americamysis bahia in Estuarine Environments" (2014). Theses and Dissertations (Comprehensive). 1631.
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