Fluffy food: Assessing microplastic and natural fibre interactions with biofilms and aquatic invertebrates in rivers, lakes, and the sea

Microplastic particles are ubiquitous pollutants that pose both a physical and chemical threat to the environment and organisms. Their presence in different environments has been confirmed globally, however, the transport of microplastics through the environment is influenced by physical and biological processes that vary considerably through space, and are far from understood. Moreover, microplastic particles are not the only anthropogenic particulate pollutants in the environment.

Natural textile fibres, especially cotton, have been found to be the dominant textile fibre type in studies that have quantified both natural and plastic textile fibres in the environment (Stanton et al. 2019). The physical and biological processes that influence the transport and distribution of natural fibres have not been studied at all.

The physical factors that influence the pathways of anthropogenic microparticles in the environment can be experimentally tested and modelled, however, biological drivers of these pathways are much more variable. The interaction of biological species with particles/ materials at this length scale is altered dramatically depending on the material chemistry, shape size and particularly any smaller features presented on their surface.

Biofilms (bacterial, algal, and fungal communities that colonise solid substrates in aquatic environments) are known to colonise plastic materials (Smith et al. 2021), and influence the transport and ingestion of microplastic particles (Rummel et al. 2017).

Understanding how the variables that influence pathways of anthropogenic microparticles differ between environments is key to informing monitoring practices. Determining the relative drivers of the ingestion of these particles is also key to understanding their relative impacts on organisms and food webs in different environments.

This PhD will assess the influence of polymer (natural fibres and plastic), particle size and shape, and additives (e.g. dyes) on the biofilm communities that colonise plastic and natural fibre microparticles in freshwater (river and lake) and coastal marine environments. The influence of these factors on the ingestion and egestion of these anthropogenic microparticles by aquatic invertebrates will further be investigated, with implications for microparticle transport and bioaccumulation / biomagnification.

This PhD will extend the microplastic research field considerably by combining assessments of its experimental variables in one research programme. Moreover, it's inclusion of natural textile fibres adds further novelty with implications for discourses of sustainable fashion and plastic alternatives. (Project Part 1)

It will then expose these experimentally biofilmed particles to field-caught invertebrates (freshwater macroinvertebrates, coastal zooplankton) (Project Part 2).

Working from data obtained in parts 1&2 this PhD will aim to characterise biofilms on anthropogenic particles in freshwater and coastal waters, and in the organisms that inhabit them.

o Aquaculture is an economically important but socially contentious industry, and previous work has shown that aquaculture infrastructure is a source of macro and microplastic particles.

o Aquaculture also has a chemical footprint associated with feed, pharmaceuticals, and antifouling agents that vary with environment type.

o Part 3 will compare microparticle ingestion in field organisms, and biofilm characterisation of natural and anthropogenic substrates in the English Midlands, with that in sites near to marine and freshwater aquaculture sites, building on previous research conducted by this team that has identified coastal aquaculture as a source of microplastic particles.