Habitual feeding patterns impact polystyrene microplastic abundance and potential toxicity in edible benthic mollusks

That increasing microplastics (MPs, <5 mm) eventually end up in the sediment which may become a growing menace to diverse benthic lives is worthy of attention. In this experiment, three edible mollusks including one deposit-feeding gastropod (Bullacta exarate) and two filter-feeding bivalves (Cyclina sinensis and Mactra veneriformis) were exposed to polystyrene microplastic (PS-MP) for 7 days and depurated for 3 days. PS-MP numbers in the digestive system and non-digestive system, digestive enzymes, oxidative stress indexes, and a neurotoxicity index of three mollusks were determined at day 0, 3, 7, 8 and 10. After seven-day exposure, the PS-MP were found in all three mollusks' digestive and non-digestive systems. And PS-MP in M. veneriformis (9.57 ± 2.19 items/individual) was significantly higher than those in C. sinensis (3.00 ± 2.16 items/individual) and B. exarate (0.83 ± 1.07 items/individual) at day 7. Three-day depuration could remove most of the PS-MP in the mollusks, and higher PS-MP clearance rates were found in filter-feeding C. sinensis (77.78 %) and M. veneriformis (82.59 %) compared to surface deposit-feeding B. exarate (50.00 %). The digestive enzymes of B. exarate significantly reacted to PS-MP exposure, while oxidative responses were found in C. sinensis. After three-day depuration, the changes of digestive enzymes and the oxidative states were fixed, but neurotoxicity induced by PS-MP was not recoverable. Besides, it is noteworthy that changes of digestive enzymes and acetylcholinesterase are related to feeding patterns.