The effects of expanded polystyrene particle on energy metabolism of the sea slater (Ligia cinerascens) originating from a highly EPS-polluted area.

Due to its high concentration and persistence, microplastic (MP) pollution is a major threat to marine environments. Expanded polystyrene (EPS) particles are the most abundant MP type in Asian regions, including the Korean coastal region. Although many previous studies have reported the toxicity of MPs to marine biota, the toxicity of environmentally relevant MPs to coastal organisms is not well understood. Thus, we investigated the toxicity of EPS on the growth and energy metabolism of the juvenile marine isopods, Ligia cinerascens, obtained from a population that has been exposed to EPS through multiple generations. After 14 and 21 days of dietary EPS exposure, body weight and molting of L. cinerascens were unaffected. However, the energy reserves (carbohydrates, proteins, and lipids) were significantly reduced, resulting in a decrease in the total energy budget (E_a) by dietary EPS exposure. The transcriptional modulation patterns of genes related to energy metabolism suggested that dietary EPS exposure may increase the digestion of non-carbohydrate sources, such as proteins and lipids, to compensate for increased energy expenditure. Our findings suggest that dietary EPS exposure, although no toxic at the individual level, can reduce the energy status of juvenile marine isopods, which provides useful information on the toxic effects of environmentally relevant MPs to coastal ecosystem.