Effects of accumulation of acrylic microfibers on algal ingestion, growth, and survival of spat of slipper-cupped oyster Magallana billeneata (Röding 1798)

Microplastics (MPs) are a growing concern globally but ecotoxicological studies assessing the effects of the most abundant MP morphotype, microfibers, remain limited. Here, we investigated the concentration-dependent effects of acrylic microfibers (AMFs) on spats of commercially important slipper cupped oyster (Magallana bilineata). Oyster spats (55-d post fertilization, 1-5 mm) were sub-chronically (30-d) exposed to 0, 1, 10, 100 AMF mL as treatments and sub-samples were periodically collected to determine AMF ingestion and changes in spat survival, growth rate, and algal ingestion rate. As early as week one, spats were observed to be covered with AMFs, and pseudofeces-AMF aggregates indicated possible ingestion and egestion of AMFs by spats. Further, lower algal ingestion rates by the oyster spats were observed after exposure to high AMF concentration (100 AMF ml) and was accompanied by slowed growth rates across all treatments after two weeks of exposure. Although no mortality occurred and some recovery was observed during the 3rd to 4th weeks, the growth rates of spats exposed to 100 MP mL remained significantly lower than that of spats in the other treatments and controls across time points, suggesting irreversible effects on oyster fitness after exposure to high AMF concentrations. These observed responses of oyster spats to AMFs could potentially indicate ecotoxicological effects of MPs. While lasting effects were restricted to the highest exposure concentration, continued increases in environmental microplastic contamination could potentially result in exposure levels capable of eliciting comparable biological responses in the future, ultimately, affecting oysters in both the wild and aquaculture setting.