Interim report: Quantification of microplastic and plastic additives in water and fish in RAS (WP1)

Abstract

Plastic material has been collected from three recirculating aquaculture systems (RAS) and their infrastructure. All plastic sources were analysed to identify their polymer and additive contents and a reference library created. This was used for targeted analysis when investigating the presence of microplastics within RAS facilities, specifically looking at intake water, recirculating water, sludge, fish, and fish feed. Analysis of these samples showed low levels but identified several potential sources of microplastics, including plastic infrastructure and consumables. There were low numbers of microplastics >300 μm in RAS samples. Comparatively, particle analysis of the smaller size fraction (50-300μm) suggests some degree of microplastic generation within the RAS although data is limited. Potential sources originating from the RAS infrastructure were identified as the fix bed bioreactor (FBBR) and moving bed bioreactor (MBBR), and biomedia. Initial analysis of fish tissue and stomachs showed low levels of microplastic and based on these results no conclusion could be drawn on ingestion by the fish. Screening for additives identified that several plastic-related chemicals were ubiquitous in RAS recirculating waters, including selected antioxidants and plasticisers. The source and distribution of these chemicals was compound specific. Fewer chemicals were quantified in sludge and fish compared with water. But specific compounds including antioxidants and plasticisers were consistently found in fish.