Creation of an international laboratory network towards global microplastics monitoring harmonisation.

Infrastructure is often a limiting factor in microplastics research impacting the production of scientific outputs and monitoring data. International projects are therefore required to promote collaboration and development of national and regional scientific hubs. The Commonwealth Litter Programme and the Ocean Country Partnership Programme were developed to support Global South countries to take actions on plastics entering the oceans. An international laboratory network was developed to provide the infrastructure and in country capacity to conduct the collection and processing of microplastics in environmental samples. The laboratory network was also extended to include a network developed by the University of East Anglia, UK. All the laboratories were provided with similar equipment for the collection, processing and analysis of microplastics in environmental samples. Harmonised protocols and training were also provided in country during laboratory setup to ensure comparability of quality-controlled outputs between laboratories. Such large networks are needed to produce comparable baseline and monitoring assessments.

Macrolitter and mesolitter in the Thames Estuary: A temporal litter assessment and brand audit of submerged and riverbed debris.

Macroplastic is a growing concern for marine environments with estuaries providing a major pathway for pollution from land-based sources to the sea. In the Thames Estuary, plastic was abundant floating below the surface and on the riverbed, with an average catch per unit effort of 0.57 ± 0.42 and 2.75 ± 2.44 item per minute respectively. Whilst the abundance of litter differed between midwater and benthic zones, the types of products recovered did not. These were identified through visual examination and use of a unique citizen science engagement protocol, allowing for the item age, brand and countries of origin to be established. The majority of litter from the present study (n = 1335) was packaging (40%), some of which was over 30-years old and may have originated from landfill run off. Also abundant was sewage-related debris, the inputs of which was related to heavy or prolonged rainfall. Peaks in this material were recorded in September 2020 following the greatest volume of rain recorded in a single day and in June 2019 after the longest period of continuous rainfall. The Covid-19 pandemic did not influence the abundance or diversity of plastic recovered between December 2018 and September 2020. The durability of plastic ensures it has high potential for harm through entanglement, deoxygenation of sediment and ingestion. The retention in the environment also increases opportunities to fragment into micro- or nanoplastics and, therefore, it is important to monitor plastics at both a macro- and micro-scale.

High prevalence of plastic ingestion by Eriocheir sinensis and Carcinus maenas (Crustacea: Decapoda: Brachyura) in the Thames Estuary.

This study presents evidence for microplastic contamination in two resident species of brachyuran crab from the Thames Estuary: the native shore crab, Carcinus maenas (Linneaus, 1758) and the invasive Chinese mitten crab, Eriocheir sinensis (H. Milne Edwards, 1853). The gills, gastric mill and intestine of 94 C. maenas and 41 E. sinensis were examined. Crabs were sampled periodically (ca. every three months) between December 2018 and October 2019. A total of 874 plastics were recovered, ranging 34 µm-34 mm in length. Overall, 71.3% and 100% of C. maenas and E. sinensis, respectively, contained at least one item (fibre, film, fragment or tangle of fibres) in the gill chamber, gastric mill or gastrointestinal tract. The most common items were fibres (78.5%) but in some cases, particularly in the gastric mill, these were aggregated into tangles (7.8%). Almost all E. sinensis contained tangles of fibres (95.1%), whereas, relatively few C. maenas contained similar tangles (10.6%).

Ingestion of plastic by fish: A comparison of Thames Estuary and Firth of Clyde populations.

This study compared plastic ingestion between pelagic and benthic fish populations from two UK watersheds: the Thames Estuary and the Firth of Clyde. The alimentary canals of 876 individuals were examined. Of twenty-one estuarine species investigated, fourteen ingested plastics, including predator (fish) and prey (shrimp) species. Overall, 32% of organisms ingested plastic, mostly fibres (88% of total plastics). More flatfish (38%) ingested plastics than other benthic species (17%). In the Thames, more plastic was ingested by pelagic species (average number of plastic pieces ingested: 3.2) and flatfish (average number of plastic pieces ingested: 2.9) than by shrimp (average number of plastic pieces ingested: 1). More fish from the Clyde ingested plastic than similar Thames species (39% compared to 28% respectively); however, the average amount of plastic ingested did not differ between the sites.