Biodynamic modelling of the bioaccumulation of arsenic by the polychaete Nereis diversicolor

Environmental context Models that explain the uptake and bioaccumulation of an element in an aquatic ecosystem are valuable for predicting its potential ecotoxicity in coastal areas. Arsenic is a toxic element that is strongly adsorbed to sediments, offering a potential risk to deposit-feeding invertebrates, and ultimately to consumers higher up coastal food chains. This study uses biodynamic modelling to predict the uptake and accumulation of arsenic from water and sediment in a deposit-feeding polychaete worm that is a major source of food to fish and wading birds in estuaries. Abstract Arsenic (AsV) uptake and bioaccumulation from water and ingested sediment by the deposit-feeding polychaete Nereis diversicolor has been investigated using biodynamic modelling. Worms accumulated As from solution linearly at dissolved concentrations from 2 to 20 µg L–1 (uptake rate constant 0.057 l g–1 day–1 at 10°C, 16-psu salinity), and the As assimilation efficiency from ingested sediment was 28.9%. Efflux rate constants of As taken up from water and ingested sediment were 0.0488 and 0.0464 day–1 and did not differ significantly. Sediment As concentrations, ranging from very high to low, were measured at eight estuarine sites, and the model predicted accumulated As concentrations in resident N. diversicolor. Comparisons of predicted against independently measured As concentrations in locally collected worms showed that the model generally performed well, highlighting the potential of biodynamic modelling in predicting the uptake and therefore ecotoxicity of As in estuarine sediments.