Modelling the Uptake and Exchange of Microplastics in Marine Ecosystems using a Novel, Integrated System of High-Resolution Numerical Models

Microplastics are small plastic particles that are less than 5mm in size. They are abundant and ubiquitous in the marine environment and their concentration is expected to increase in future years alongside the increasing plastic production rates. The detrimental impacts of mPs in the marine environment has led to their indication as an area of concern in the EU Marine Strategy Framework Directive (MSFD 2008/56/EC) and their inclusion within OSPARs North-East Atlantic Environment Strategy Strategic Objective 4, which aims to "prevent inputs of and significantly reduce marine litter, including mPs, in the marine environment to reach levels that do not cause adverse effects to the marine and coastal environment with the ultimate aim of eliminating inputs of litter". Concerns surrounding marine mP pollution have been compounded by recent studies which have demonstrated that plastic pollution can induce unique pathologies, such as 'plasticosis' in seabirds and have evidenced the uptake of mPs by humans through their presence in human bowels, faeces, blood, and placenta. Therefore, it is of critical importance that we understand the potential ecological harm that may be caused by marine mPs.

mP pollution is a multi-faceted issue presenting environmental and public health problems which can only be fully understood through integrated, multi-disciplinary research. To fully comprehend the impacts of mPs in the marine environment and ascertain levels of mP pollution which will not cause adverse effects, it is vital that there is an understanding of their potential sources and sinks, their mode of transport and the processes driving their uptake and exchange within the marine environment. However, the current lack of understanding of these processes prevents such activities from being undertaken. This research aims to contribute towards addressing the knowledge gaps surrounding marine mPs and increase our understanding of the processes driving the uptake and exchange of mPs in marine ecosystems by developing a system of numerical models to simulate these processes at lower trophic levels (phytoplankton and zooplankton) in the northwest European Continental Shelf region.

This information is also essential for policy makers to complete a risk assessment of mPs in the marine environment. There must be a strong dialogue between researchers and policy makers to disseminate the information and enable science-based decision making that translates relevant research into action to mitigate against marine plastic pollution. Accordingly, this research will contribute information to policy makers that is relevant to the management and mitigation of marine mP pollution.

The objectives of this research are (A) to improve the understanding of the processes which are significant in driving the uptake and exchange of mPs at lower trophic levels in marine ecosystems by conducting a review of potentially important processes, (B) to develop a mathematical model system to investigate the importance of the identified mP uptake and exchange processes at lower trophic levels in marine ecosystems, (C) to increase the understanding of the potential sources and sinks of mPs in marine ecosystems by investigating the potential means of parameterising the riverine input and atmospheric deposition of mPs to the marine environment in the northwest European continental shelf region and (D) to utilize the research findings to provide relevant information and recommendations to policy makers relating to the assessment of the risks posed by mP pollution and their potential to cause significant ecological harm and the implementation of suitable mitigation measures to reduce the environmental impacts of mPs.