Modelling the uptake and exchange of microplastics in marine ecosystems using a novel, integrated system of high-resolution numerical models

Six empirical models to calculate the settling velocity of regularly and irregularly shaped particles are evaluated to identify the most appropriate model for implementation within the mP model framework. The evaluation also provides evidence that the mP transport model can be simplified by assuming that the mP settling velocity is constant over time and depth. A case study is undertaken to consider implementation of the model framework in the Northwest European continental shelf region.

Data is extracted to parameterise the riverine input of mPs, which indicates that the North Sea may be exposed to significant levels of mP contamination. Spatial interpolation methods are used to collate the available data and research and make a basic, preliminary estimate of the atmospheric deposition of mPs to the model domain. Based on properties of mPs involved in interactions with lower trophic level organisms in lab and field studies, it is recommended that the mP model framework must simulate fibrous and fragment mPs that are less than 30µm in size and should include positively, negatively, and neutrally buoyant polymers.

The available data which is collated for model parameterisation, calibration and validation does not satisfy these requirements and is also impacted by further issues. Therefore, it is not currently feasible to implement the model system in this region. Thirteen recommendations are made to provide information to researchers and policy makers regarding the improvements to sampling activities, additional research and legislative measures required to obtain the necessary data to successfully implement the proposed model framework and produce relevant information for the risk assessment and remediation of mP pollution in the marine environment.<br>