Bioavailability and biological effects of microscopic plastic debris in the ocean

Every year, millions of tonnes of plastic debris is discarded as waste and marine plastic litter is emerging as both a threat to the oceans and a major challenge for society to manage. Once plastic waste has entered the sea, the combined action of winds and tides leads to the fragmentation of larger plastic debris into microscopic particles. These microscopic particles have become so numerous, either floating in the ocean or accumulating in sediments and on shorelines, that they are emerging as a global conservation issue of high concern.

We have been studying what happens when microplastics are ingested by marine organisms at the lower end of the marine food web, including zooplankton that swim and feed in surface waters and marine worms that live in sediments at the ocean bottom. In our laboratory studies, ingestion of microplastics alongside food items led to reductions in body mass and reproduction. After the particles had been egested, they sank more slowly in the water column. This is important because the biomass of zooplankton and worms (so-called secondary producers) and the sinking rates of faecal pellets, are extremely important for the cycling of carbon and other nutrients in the oceans, which in turn is central to supporting all marine life.

In this proposal, we will build on these early findings to determine their significance for ocean life. We will study in detail how much microscopic plastic is actually being ingested by zooplankton collected from sites near to shorelines in UK waters. We will take samples from across a yearly cycle to understand how the abundance of plastic debris and its ingestion by zooplankton vary with seasonal cycles. We will study the factors such as size, shape and type of plastic that influence how much microplastic is consumed and the biological effects that it may have on organisms in the aquarium.

We will enter these results into models of ocean functions to predict what sites, if any, are most vulnerable to microplastics contamination and where the densities of microplastics may become comparable to those of invertebrate prey items. We will then use models to predict the impacts of this contamination on important ocean functions, such as the types of animals present and the cycling of both carbon and nutrients throughout the water column.

This project will provide important scientific results to improve our understanding of key ecological functions in the oceans, illustrate how our discarded waste materials may be capable of impacting on important ocean processes, and may highlight vulnerable sites or species that require special protection. This data will be of use to environmental managers and policy makers who are required by law to keep our seas clean and reduce the risk of direct or indirect harm to human and ocean health. Ultimately the results are important to everyone in society, and may help to build up a body of evidence to encourage us not to litter in the first place.

This research project has been designed with direct input from stakeholders involved in marine litter from the very start and is designed to have an impact beyond its immediate academic environment. Its influence will be principally within the academic disciplines of the applicants, ecotoxicology, molecular ecology and biogeochemical modelling of ocean processes, but will extend to the environmental risk assessment and marine sciences communities and the scientists and policy professionals concerned with environmental protection.

The main group to benefit from the results of this research will be ecotoxicologists who are concerned with understanding how environmental pollutants interact with living systems, and molecular ecologists who study the mechanisms of temporal and spatial control of gene activity and its relationship with physiological function. Scientists in these disciplines will benefit from the specific information relating to microscopic marine plastic debris, its bioaccumulation, interaction with body systems and potential to influence large scale ocean processes.

In addition, human and ecological risk assessment professionals concerned with the international regulation of chemicals and substances will be interested in the results, since the safety assessment of environmental substances requires a sound weight of scientific evidence on which to base regulatory decisions. To adequately assess the risks posed by marine litter and the chemicals that may be associated with it, we need to know about their inherent properties of the chemicals and polymeric substances themselves (hazard) and to what extent organisms come into contact with them (exposure). A better appreciation of the ways in which marine litter is processed by regulatory systems in the body and the wider influence that this may have at the population level presents a subject of huge potential interest and relevance.

This will also be of potential interest to organisations such as the Food Packaging Forum which is a charitable, non-profit organisation established to identify and communicate high quality scientific information about food contact materials, their health implications and patterns of discard and recycling, since so much of the marine litter in the environment is derived from food packaging. Individuals in the plastics industries (through organisations such as Plastics Europe) and their associated groupings, such as the Global Polymer Innovations network and related Green Chemistry initiatives are all relevant and likely to be interested, since most manufacturers are very keen to work towards reducing marine litter and would be helped with directly relevant data on what impact it may be having

Finally, those charged with implementing policies designed to protect the marine environment will be interested in the results of our research. The Marine strategy Framework Directive (MSFD) Descriptor 10: Marine Litter (see pathways to impact for more details) is implemented through the OSPAR commission (Oslo Paris Convention) and ICES (International Council for the Exploration of the Seas). OSPAR's research priorities relating to marine litter are coordinated through the EU Technical Review Group on Marine Litter (part of the OSPAR Environmental Impact of Human Activities Committee, EIHA). The MSFD requires that all EU member states consider how Good Environmental Status (GES) for that descriptor will be achieved by 2020. Thus there is a huge policy driver to identify how marine litter and microplastics in particular may be impacting on marine life and how to set realistic targets to control marine litter. (see pathways to impact section for further details of our policy interactions).