Seafloor sediments have been defined as sinks for microplastics in the marine environment and could therefore represent suitable matrices for their long-term monitoring. On a regional aspect, the adoption of a common indicator for microplastics in seafloor sediments would allow regional monitoring and assessments through international frameworks such as OSPAR. This study presents the findings of a research and development project monitoring the occurrence and abundance of microplastics in UK seafloor sediments for the period 2013-2021, supporting the development of a national monitoring programme for microplastics in seafloor sediments for the UK (England and Wales). A fast-screening technique based on Nile Red staining of polymers coupled with µ-FTIR was applied and validated using µ-FTIR-FPA. Microplastic particles were detected in all 189 sediment samples from 15 stations selected around the UK for each investigated year (2013 - 2021). Microplastic concentrations (20 – 5000 µm) ranged from 133 – 6,933 particles kg-1 dry weight sediment for 2020-2021. Microplastics mainly consisted of fragments (73%), fibres (19%) and spheres (8%). Plastic fragments ranged from 46 to 3276 µm and plastic fibres from 300 to 1731 µm in length with a mean diameter of 16 µm. Single particle analysis using µ-FTIR indicated a prevalence of Rayon, PP, Rayon/Nylon/Polyester blends, Rubber, PS, PE, PA, PVC, Acrylic, EMAA and PET. Fragments were mainly white in colour (46%) followed by brown (38%), black (1%), blue (1%) and orange (1%). Fibres were mainly white in colour (57%) followed by black (14%), orange (14%) and red (14%). A trend assessment at the UK regional seas levels indicated little visual evidence of any trends in the abundance of microplastics over time in any of the regional seas – with the possible exception of the Northern North Sea with a reduction in abundance over time for the time-period 2013-2021.

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Diego Garcia is the largest atoll within the Chagos Archipelago in the Indian Ocean. Since the 1960s it has been a military base, populated only by military and support personnel. Infrastructure includes sewage treatment works, a waste disposal facility and an airbase. Lagoon use includes boating and large vessel anchorage. Current pollution levels by inorganic nutrients and other contaminants are unknown. A field study was undertaken in March 2019 to obtain baseline information on key environmental parameters and pollutants for assessing the state of marine water quality. Outside the atoll, three stations were sampled where human impacts were likely to be lowest (two off the north coast, considered as ‘near-pristine’; one on the east coast); one station was sampled in the lagoon mouth; 10 stations were sampled downstream from two sewage outflows. Inside the lagoon, 10 stations were sampled at near-shore sites likely to be directly impacted by activities such as boating and waste management; six stations were sampled in the central or eastern lagoon. In situ sensors were used to estimate temperature, salinity, chlorophyll (as fluorescence) and dissolved oxygen. Discrete water samples were analyzed for nutrients, chemical contaminants, heavy metals and fecal indicator bacteria. Sea surface temperatures were highest (29.5–35 °C) inside the lagoon; salinities were generally higher (> 34.1) outside the lagoon (vs 33.8–34.1 inside). Surface nutrient concentrations at near-pristine stations were undetectable for nitrate and phosphate and averaged 1.39 μM for dissolved inorganic nitrogen (DIN) and 1.73 μM for silicate. Concentrations were higher at most other stations (maximum 5.7 μM DIN, 0.38 μM phosphate, and 9.93 μM silicate), with ammonium contributing most to DIN. In the lagoon, chlorophyll concentrations were relatively low (0.3 – 0.6 μg chl l–1) near the surface and higher (max 0.9 μg chl l–1) at depth. Results suggested low levels of pollution overall. However, levels of nutrients, oxygen deficiency, chemical contaminants (e.g., solvents and DEET) and heavy metals (cadmium, nickel, zinc and copper) at some sites inside the lagoon are a concern due to slow flushing rates and will be used to inform future monitoring and assessment of environmental health at Diego Garcia.

The global COVID-19 pandemic of 2020 has forced small island states to make rapid changes to the way they manage their marine estates following changes in global shipping practices and access which are essential for the supply of food items and island’s infrastructure. Following the closure of the border of neighboring French Polynesia, changes had to be made to the Pitcairn Islands’ sole supply vessel route, which resulted in the vessel requiring to set anchor on arrival at the island to conserve fuel. Considering this change and to ensure the continued protection of vulnerable coral habitats the local government has had to make swift decisions to identify anchoring zones that minimize seabed disturbance. Data collected in January 2020, just prior to the pandemic, were assessed using a rapid assessment method and combined with earth observation data to create the first shallow water (<∼20 m) habitat map of this island. The results show the distribution of vulnerable coral communities and other habitats, achieving an accuracy of 68% compared with previously collected datasets making the results the best available evidence for management purposes. Although the seabed data were not originally collected for this analysis, having both video and stills imagery aligned with global positioning meant a rapid assessment method could be easily applied to the data. The assessment technique used has resulted in the first reliable habitat distribution maps to be produced in a management critical timeframe, providing managers with the evidence they required to make informed decisions relating to the protection and conservation of Pitcairn’s pristine, marine habitats during these unprecedented times.

The coral reefs of the Pitcairn Islands are in one of the most remote areas of the Pacific Ocean, and yet they are exposed to the impacts of anthropogenic climate change. The Pitcairn Islands Marine Protected Area was designated in 2016 and is one of the largest in the world, but the marine environment around these highly isolated islands remains poorly documented. Evidence collated here indicates that while the Pitcairn Islands' reefs have thus far been relatively sheltered from the effect of warming sea temperatures, there is substantial risk of future coral decalcification due to ocean acidification. The projected acceleration in the rate of sea level rise, and the reefs' exposure to risks from distant ocean swells and cold-water intrusions, add further uncertainty as to whether these islands and their reefs will continue to adapt and persist into the future. Coordinated action within the context of the Pitcairn Islands Marine Protected Area can help enhance the resilience of the reefs in the Pitcairn Islands. Options include management of other human pressures, control of invasive species and active reef interventions. More research, however, is needed in order to better assess what are the most appropriate and feasible options to protect these reefs.