Nature-based solutions to the management of legacy plastic pollution: Filter-feeders as bioremediation tools for coastal microplastics

Plastics are one of the most topical pollutants occurring in our ocean. Given concern regarding the impacts of both macro- and micro-plastics on environmental and human well-being, a range of management approaches are required. Key in the management of microplastics will be curative measures that facilitate the removal of legacy plastics from the environment as, without their removal, impacts will continue for centuries. While a strong focus has been placed on technical, engineered solutions to plastic removal, many of these techniques are unsuitable for microplastics. Therefore, here we argue for the exploration of nature-based solutions to such issues. As a case study, we combine information available in the published academic literature with experimental results from a pilot study to highlight the potential for filter-feeding organisms - specifically mussels - to remove microplastics from the water column by transferring them into biodeposits. Such biodeposits have the potential to be transported to other parts of the system (i.e., benthic regions), or collected and removed from the environment. While initial results indicate that such approaches are promising for microplastic removal from water sources, there are a number of areas that still need investigation before widespread application of such an approach could be adopted. Key knowledge gaps include identification of the appropriate methods to be used and assessment of unintended consequences including potential impacts of microplastics on benthic organisms. We argue that there is a need for ongoing funding and policy support for the development and application of such nature-based solutions targeting legacy plastic pollution.