Investigating the effects of PLA microplastics on Pocillopora damicornis (cnidaria, scleractinia)

While the harmful effects of synthetic microplastics on reef-building corals are well documented, the impacts of their bio-based counterparts remain largely understudied. In this study, we investigate the chemical and physical properties of mechanically grounded polylactic acid microplastics and assess their short-term effects on the physiology and cellular oxidative state of the scleractinian coral Pocillopora damicornis. The microplastics, obtained by mechanical grinding, exhibit a wide size distribution, with 90% of particles ≤370 μm and 50% ≤ 192 μm. They display irregular size and rough surface, along with reduced crystallinity and molecular weight compared to the original pellets. Coral colonies were exposed to three microplastic concentrations (5 mg/L, 15 mg/L, and 50 mg/L) for 72 h, and no mortality or signs of bleaching were observed in all cases. Although colonies exposed to the higher concentration exhibited an increase in the activity of the antioxidant enzyme glutathione reductase, no significant cellular oxidative damage was caused by the microplastics, as the lipid peroxidation analysis indicated. This study provides a preliminary assessment of the physiological effects of polylactic acid microplastics on stony corals, emphasizing the need for further research on bio-based contaminants and their impact on marine benthic organisms.