Bioturbation by Scopimera globosa enhances sediment-water fluxes of microplastics and associated phthalates: Exposure pathways and ecological risk.

Estuarine sediments are major sinks for microplastics (MPs) and plasticizers, yet bioturbation may alter their retention and re-exposure. Here, we used laboratory experiments with Scopimera globosa (De Haan, 1835) to examine how crab burrowing affects the transport of different MPs (PVC fragments, PP fragments, and PP fibers) and their added phthalate esters (PAEs) in sediments. Crab activity significantly increased upward MPs transport, suggesting a potential shift of sediments from a sink toward a more dynamic source. PVC fragments showed the highest removal from the sediment and the greatest increase in the overlying water. Disturbance also appeared to enhanced the desorption and migration of phthalate plasticizers from polyvinyl chloride microplastics, leading to elevated plasticizer concentrations in surface sediments and the water column. Although MPs were not detected in crab tissues, exposed individuals showed clear behavioral changes, including shallow dwelling, reduced activity, and prolonged re-burial. These responses were accompanied by significant alterations in neural, energy metabolic, and oxidative stress markers, suggesting potential combined stress from environmental disturbance and plasticizer exposure. Controlled laboratory experiments suggest that benthic crustacean bioturbation may redistribute MPs and associated PAEs in sediments, highlighting bioturbation as a potential regulator of MPs mobility and a process that warrants consideration in MPs risk assessments, pending further field validation.