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Impacts of emerging pollutants on early development of marine invertebrates : case studies on microplastics and interaction between fluoxetine and ocean acidification
Summary
Researchers measured environmentally relevant fluoxetine concentrations in Hong Kong waters and exposed larval sea urchins and sea squirts to the pharmaceutical under both present and projected acidified ocean conditions, finding that ocean acidification modulated toxicity in both species and that the two species responded very differently, underscoring the importance of multi-stressor and multi-species designs in pollution assessments.
Exposure to emerging pollutants has put marine organisms living in the coastal environments at risk. However, the ambient concentration of these emerging pollutants is poorly understood in Hong Kong. This dissertation is the first to measure the ambient concentrations of fluoxetine in Port Shelter, Hong Kong. With the measured concentration of fluoxetine in eastern Hong Kong waters, I studied its impacts on larval marine invertebrates under environmentally-relevant concentrations. This dissertation research is also the first of its kind to modify the protocol of comet assay to reliably detect DNA strand break in larvae exposed to a stressor at environmentally-relevant concentrations across various phyla. Very often, the adverse impacts of ocean acidification (OA) or exposure to pharmaceuticals were studied alone. However, little is known about the interactive effect between fluoxetine and OA, even when the bioavailability of many pharmaceuticals is pH-dependent and/or the two stressors act upon similar physiological pathways. Even if the interactive impacts on a single species were thoroughly understood, it is still unclear how such observed impacts could be translated to other species. Here, I exposed larval sea urchins Heliocidaris crassispina to the environmentally relevant concentration of fluoxetine (10 and 100 ng L-<sub>1</sub>) under present-day (pH 8.0) and future ocean conditions (pH 7.7). Then, I took a comparative approach and exposed larval Styela plicata to a similar set of conditions. The impacts of fluoxetine exposure on both species were modulated by OA. However, the impacts on the early development of S. plicata were much subtler than that observed in H. crassispina. This study's results highlight that future studies on ecological risks should consider interactive effects and differences in life-history traits before concluding how the stressor(s) could affect the population and community structures.