Measuring the physiological responses of Pocillopora acuta to biofilmed polyethylene microplastics exposure stress

Abstract

Microplastics are a prevalent pollutant in today’s environment, particularly in marine ecosystems. These polymers allow the establishment of bacterial biofilms on their surfaces, which lead to the concentration of certain bacterial species on their surface. Corals reside in shallow, coastal regions of the ocean, where microplastics have been found to accumulate. They are also suspension feeders which increases their exposure to microplastics. The ingestion of these polymers have been shown to harm the health of corals, resulting in coral bleaching and tissue necrosis. In this project, the relationship between Pocillopora acuta’s exposure to polyethylene tetraphthalate microplastics, both biofouled with Pseudoalteromonas, a widely known symbiotic bacteria with corals, and non-biofouled is examined through a week-long ex-situ experiment, using mini-vortex resuspension tanks. The results of the experiment show a statistically signficant difference between treatments in terms of coral colour (measured with the coral health chart) and Symbiodiniaceae density, which are two common methods in assessing coral health. However, due to the lack of sufficient replicates, the pair-wise post-hoc analyses do not show a statistically significant difference between treatment pairs. Interestingly, the results hint towards inter-colonial differences which may help to explain the differences in stress responses of the corals.