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Microplastics reduce pyrene bioaccumulation and trophic transfer in brine shrimp–marine medaka food chain: the role of sorption versus biotransformation
Original title: Microplastics reduce pyrene bioaccumulation and trophic transfer in brine shrimp–marine medaka food chain: the role of sorption versus biotransformation
Summary
Scientists studying tiny sea creatures found that when a common pollutant (found in things like grilled food and vehicle exhaust) sticks to microplastics, fish actually absorb less of it compared to when the pollutant is floating freely in water — likely because their bodies break it down and flush it out more easily. This is somewhat reassuring news suggesting microplastics may not always make chemical pollution worse as it moves up the food chain, though the researchers caution the pollutant still ended up in the fish's body tissues (not just its gut), meaning eating contaminated seafood remains a potential concern worth further study.
Microplastics (MPs) can sorb hydrophobic organic pollutants and alter their environmental bioavailability, yet their impact on pollutant bioaccumulation at higher trophic levels in food chains remains obscure. Here, we investigated the effects of MPs (150-200 μm) on the accumulation and trophic transfer of pyrene in a simplified marine food chain comprising brine shrimp (Artemia salina) and marine medaka (Oryzias melastigma). By utilizing brine shrimp nauplii, which are too small to ingest the MPs, we isolated the dietary transfer of pyrene from the interference of direct MPs ingestion by prey. Using C-labeled pyrene, we quantified bioaccumulation in marine medaka via three pathways for 48 h: uptake of free pyrene, MPs-associated pyrene, and brine shrimps (diet)-associated pyrene. The bioconcentration factor of MPs-associated pyrene in marine medaka was significantly lower than that of free pyrene, while dietary exposure contributed minimally to accumulation. Although not statistically significant, biomagnification factors tended to be higher in marine medaka fed brine shrimps exposed to free pyrene than those exposed via MPs. For all exposure routes, radioactivity primarily localized in non-intestinal tissues, indicating potential risks to human consumers. Hydrophilic pyrene metabolites (1-hydroxypyrene and 1-pyrenyl sulfate) were identified in both species, suggesting that biotransformation increases hydrophilicity, facilitates excretion, and consequently mitigates bioaccumulation and trophic transfer. These findings provide insights into the effects of MPs on bioaccumulation of organic pollutants in marine food chains and underscore that the ecological risks of organic pollutants are determined by the interplay between MP sorption and biological metabolism.