Modelling mussel ( Mytilus spp.) microplastic accumulation

Abstract. Microplastics (MPs) are a contaminant of growing concern due to their widespread distribution and interactions with marine species, such as filter feeders. To investigate the MPs accumulation by wild and cultured mussels, a Dynamic Energy Budget (DEB) model was developed and validated with the available field data of Mytilus edulis (wild) from the North Sea and Mytilus galloprovincialis (cultured) from the North Ionian Sea. Towards a generic DEB model, the site-specific model parameter, half saturation coefficient (Xk) was applied as a power function of food density for the cultured mussel, while for the wild it was calibrated to a constant value. The DEB-accumulation model simulated the uptake and excretion rate of MPs, taking into account environmental characteristics (temperature and chlorophyll-a). An accumulation of MPs equal to 0.64 particles individual−1 (fresh tissue mass 1.9 g) and 0.91 particles individual−1 (fresh tissue mass 3.4 g) was found for the wild and cultured mussel respectively, in agreement with the field data. The inverse experiments investigating the depuration time of the wild and cultured mussel in a clean from MPs environment showed a 90 % removal of MPs load after 3 and 14 days, respectively. Furthermore, sensitivity tests on model parameters and forcing functions highlighted that besides MPs concentration, the accumulation is highly depended on temperature and chlorophyll-a of the surrounding environment. For this reason, an empirical equation was found relating directly the concentration of MPs in seawater, with MPs accumulation in mussel’s soft tissue, temperature and chlorophyll-a.