MICROPLASTIC POL LUTION BUDGET ASSESSMENT of DIFFERENT Integrated multi-trophic aquaculture (IMTA) systems
Introduction - The expansion of the industry and increased diversity of materials used to build and maintain open and recirculating aquaculture systems (RAS) have paralleled the development and use of synthetic polymers over the last decades. Synthetic materials offer greater strength and durability than natural fibres for construction of ropes, infrastructures, and pipes, whilst often also being less costly and easier to handle. Broken and fragmented equipment as well as debris released from intense use are however sources of plastic emission from aquaculture operations at a local and global level, whilst accurate estimations of their contribution remain unknown. The ASTRAL project focuses on IMTA farming, aiming at defining, supporting, and promoting this type of sustainable aquaculture production across the Atlantic area. ASTRAL is looking at the challenges related to the release of microplastics from aquaculture operations in both open and recirculating systems as well as quantifying the marine derived sources of plastics impacts.
Materials and Methods -Four sites were selected within the present study: A) the coastal open low-trophic aquaculture facility ‘Port-a-Bhuiltin’ (Scotland); B) the coastal open multi-trophic aquaculture facility ’Lehanagh Pool’ (Ireland); C) The onshore partially (50%) recirculating multi-trophic aquaculture facility ‘Buffeljags Abalone’ (South Africa); and D) the onshore recirculating multi-trophic aquaculture facility ‘Rio Grande do Sul’ (Brazil) . T he occurrence of plastic was investigated in the seawater at increasing distances from the open systems aquaculture facilities . In the RAS systems the sampling was performed in the water inlet, outlet, as well as in some selected areas inside the recirculating system . For the seawater collection a Compact Large Volume Microplastics sampling device was developed. Extracted samples were analysed first by µ-FTIR (Fourier Transform Infrared) microscopy and finally by GCMS-pyrolysis technique.
Results and Discussion - The evaluation of the seawater samples and sediments using a vibrational microscopy-oriented technique showed the occurrence of 29 different polymer types. Among them the most recurring ones were polyethylene ( PE), polystyrene (PS), polypropylene (PP), ethyl vinyl acetate (EVA), polycarbonate (PC), polyurethane ( PU), polyvinyl chloride (PVC), polyamide (PA66) and acrylic paint (APa). The mass-based analysis confirmed the occurrence of these polymers and further detected styrene butadiene rubber as a proxy of tyre and road wear particles. The results point out a complex distribution of polymers, where the diffuse input sources in the investigated areas largely influence the observed plastic pollution distribution. The experience assessing the plastic pollution fingerprint in RAS and semi-RAS systems point out both the importance of the water quality inlet, the geographical dependent light intensity effects in plastic degradation phenomena as well as the need for an accurate r eplacement plan for teared plastic equipment. The ongoing work contributes towards an improved understanding of the complexity, introduction, and potential emission of synthetic polymers in open and recirculating IMTA systems that will contribute towards the improved sustainability of modern aquaculture systems.
Acknowledgements. E U H2020 grant agreement: 863034 - ASTRAL project (All Atlantic Ocean Sustainable, Profitable and Resilient Aquaculture.