An Ecotoxicological Assessment of the Impact of Microplastics on Daphnia magna using Acute and Chronic Toxicity Endpoints with a Focus on Stress Behaviour

Abstract

<p>Microplastics are ubiquitous in freshwater ecosystems and pose a physical and/or chemical threat to biota. While past research has focused on source, transport, and fate of this contaminant, impact assessment studies are limited. Thus, this research used <em>Daphnia magna</em>, an environmentally-relevant, model freshwater zooplankton to assess toxicity. Existing protocols were comprehensively reviewed, tested, modified, and subsequently implemented, to produce healthy, age-synchronized organisms ready for rigorous experimentation. Bioassays included microplastics (microbeads), alongside an organic contaminant, triclocarban. The thesis objectives assess whether microplastics posed a chemical and/or physical impact, either on their own, or in conjunction with an additional contaminant. Acute and chronic toxicity endpoints included mortality, reproductive, and behavioural measurements and microscopy was utilized to visualize microbeads within, and surrounding, the daphnids. Preliminary studies suggest that <em>D. magna</em> were not sensitive to environmentally-relevant concentrations of polyethylene microbeads (20-27 μm) alone. However, in conjunction with triclocarban, microbeads seemed to impact <em>D. magna</em>.</p>