Evaluating the impact of diluted bitumen and secondary clean-up methods on the phytoplankton, periphyton, and zooplankton communities of a boreal lake
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Date
2021
Authors
Perry, McKenzie
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Abstract
There is an extensive body of literature evaluating the effect of spilled oil and subsequent clean-up methods in marine ecosystems, but relatively few studies in a freshwater context. The Freshwater Oil Spill Remediation Study (FOReST) was performed to evaluate the aquatic ecosystem response to diluted bitumen and secondary oil spill clean-up methods. This thesis, as part of the FOReST study, evaluates the response of phytoplankton, periphyton, and zooplankton communities. Previously weathered diluted bitumen was applied to in-lake enclosures, followed by industry standard primary clean-up using shoreline washing and sorbent pads. The secondary treatments evaluated were: enhanced monitored natural recovery (eMNR), which is a variation of bioremediation that uses fertilizer and nutrients such as nitrogen (N) and phosphorous (P) to stimulate natural oil-reducing bacteria and shoreline cleaner Corexit EC9580ATM, to wash oil off shoreline macrophytes and into the water for further clean-up using sorbent pads. We found that the application of diluted bitumen and eMNR as a secondary oil spill clean-up method resulted in no effects on the lower-trophic levels of a boreal lake. However, the application of diluted bitumen and the SC treatment resulted in significant acute suppression of the zooplankton population. The acute suppression of zooplankton created a trophic cascade resulting in significantly higher phytoplankton biomass, likely due to predator (zooplankton) suppression, and significantly lower periphyton biomass which was likely outcompeted for nutrients by larger phytoplankton populations. These results indicate that the use of surfactants to clean-up oil spills in freshwaters can lead to increased toxicity and mortality to zooplankton, resulting in cascading effects to other trophic levels.
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Keywords
Oil, Ecotoxicology, Oil-spills, Remediation, Ecology, Aquatic Biology, Plankton, Hydrology, Freshwater