The increasing abundance of marine litter is impacting the environment, human health and economies in the South Pacific. Small Islands Developing States are particularly affected by marine litter, primarily due to insufficient waste management systems. For the first time, marine litter was quantified and characterised on 13 beaches in Solomon Islands and Vanuatu in the South Pacific region using the OSPAR beach litter monitoring guidelines. A total of 1053 (±1017) and 974 (±745) items of litter per 100 m beach were recorded in Solomon Islands and Vanuatu respectively. Litter composition and distribution show that the majority of the litter comes from local land-based sources and large quantities of fragments and single use plastics were found by cities and river mouths. Actions to reduce single use plastic, improve collection, reuse and recycling, together with outreach campaigns would reduce marine litter significantly in these countries. Furthermore, there is great potential to develop a more circular economy to manage the substantial quantities of recyclable items that were found stranded on the beaches.

Underwater noise pollution from impulsive sources (e.g. explosions, seismic airguns, percussive pile driving) can affect marine fauna through mortality, physical injury, auditory damage, physiological stress, acoustic masking, and behavioural responses. Given the potential for large-scale impact on marine ecosystems, some countries are now monitoring impulsive noise activity, coordinated internationally through Regional Seas Conventions. Here, we assess impulsive noise activity in the Northeast Atlantic reported during 2015–2017 to the first international impulsive noise register (INR), established in 2016 under the OSPAR Convention. Seismic airgun surveys were the dominant noise source (67%-83% of annual activity) and declined by 38% during 2015–2017. Reported pile driving activity increased 46%. Explosions and sonar/acoustic deterrent devices both had overall increases in reported activity. Some increases were attributable to more comprehensive reporting in later years. We discuss utilising the INR for risk assessment, target setting, and forward planning, and the implementation of similar systems in other regions.

Pollution in aquatic ecosystems is rapidly becoming one of the world's greatest ecological challenges. Given their intermediate position between terrestrial and marine environments, estuarine systems are especially vulnerable to human pollution. Amazonian estuaries have unique characteristics, such as heterogeneous landscape intercalating tracts of vegetation with sandbanks and beaches. In the present study, we provide the first qualitative and quantitative data on litter retention in an Amazonian estuary, comparing vegetated and bare substrate areas. Overall, 12,003 items were recovered, with a mean ± SD density and weight of 1.69 ± 2.16 items/m² and 78.08 ± 93.11 g/m², respectively. Plastic was the principal material (80.97%) found. The highest number of items was found in the vegetated habitats (73.11%), indicating these areas as the most affected by plastic pollution. Our findings provide important insights for future research planning and implementation of effective public policies for conservation and management of these important ecosystems.

The effects of two harmful algae Alexandrium tamarense and Gymnodinium catenatum on ecological quality status were identified using biofilm-dwelling ciliate assemblage as test organism communities. The body-size spectra of the test ciliates were observed at a gradient of cell concentrations of both algal species: 10⁰ (control), followed by10², 10³, 10⁴ and 10⁵ cells ml⁻¹. The test ciliates showed clear variations in body-size spectra along the concentration gradients of both algal species. In terms of probability density, the ciliates generally peaked at low levels of algal concentrations (10⁰–10⁴ cells ml⁻¹) in small size forms, followed by the forms with large sizes at the concentration of 10⁵ cells ml⁻¹ of both algal species. Bootstrapped-average analysis demonstrated a significant change in body-size spectrum when algal concentrations were higher than 10⁴ cells ml⁻¹. It is suggested that the body-size spectrum of the ciliates may be used to indicate the effects of harmful algal bloom.

Seagrasses have global distribution and are highly productive and economically valuable habitats. They are sensitive and vulnerable to a range of human-induced pressures, including ongoing exposure to marine litter, such as microplastic particles (<5 mm). In this study, a Zostera marina bed in Deerness Sound, Orkney was selected to determine whether microplastics accumulate in seagrass beds and adhere to seagrass blades. Sediment, seagrass blade, biota and seawater samples were collected. 280 microplastic particles (0.04 to 3.95 mm (mean = 0.95 mm ± 0.05 SE)) were observed in 94% of samples collected (n = 111). These were visually categorised into type (fibre, flake, fragment) and colour, and 50 were successfully identified as plastic using ATR-FTIR. Fibres contributed >50% of the total microplastics observed across all samples. This is the first known study on Z. marina to describe microplastic loading within a seagrass bed and to identify microplastic adherence to seagrass blades.

The current study aimed to develop a suitable molecular marker [Linear alkylbenzenes (LABs)] approach for pollution determination in mangrove oysters of peninsular Malaysia. C. belcheri species were collected from rivers of Merbok, Perai, Klang, Muar and PulauMerambong (An Island). The LABs were extracted from C. belcheri and determined using GC–MS. The LABs indices which included I/E, L/S and C13/C12 were applied to describe the sources and biodegradation of LABs. The results revealed that the maximum concentrations were detected in oysters from Klang (27.91 ng g⁻¹dw), while the lowest concentrations were detected in oysters from Merbok (8.12 ng g⁻¹dw). Moreover, I/E ratios varied between 2.83 and 6.40, indicating the secondary treatment effluents being discharged to coastal zones. The results of this study suggested that the oysters absorbed LABs mainly in dissolved phase. Therefore, mangrove oysters are a good biosensor for LABs contamination in the aquatic environment.

Due to regulations on phthalates, non-phthalate plasticizers (NPPs) are now used as an alternative. Limited studies have been conducted on the occurrence and distribution of NPPs. In this study, sediment samples were collected from 50 locations along the Korean coast to assess the occurrence, distribution, sources, and ecological risks of phthalates and NPPs. Phthalates and NPPs were detected in all sediments, indicating ubiquitous contamination of the coastal environment. Di(2-ethylhexyl)phthalate (DEHP) and di(2-ethylhexyl)terephthalate (DEHT) were dominant, suggesting that DEHT could be an emerging contaminant of concern. The highest concentrations of phthalates and NPPs were found in sediment samples from harbors, implying they are contaminated hotspots. Sedimentary organic carbon was a major factor governing the distribution of phthalates and NPPs. Significant correlations were observed among phthalates and NPPs, suggesting similar sources and geochemical behavior. DEHP concentration exceeded threshold values, indicating potential health risks to benthic organisms in sediments.

A phytoremediation experiment was carried out in mesocosms to investigate the performance of Rhizophora mangle in the remediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediment contaminated with crude oil. The water pH of the experiments (phytoremediation and natural attenuation) ranged from 4.9 to 8.4 at 0 and 90 days, respectively. The oxy-reduction potential (Eh) ranged from oxidising (108.0 mV, time 0) to reducing (approximately −110.0 mV, time 90) environments. Dissolved oxygen (DO) ranged from 5.7 mg L⁻¹ (time 0) to 4.5 mg L⁻¹ and 3.6 mg L⁻¹ (time 90) in phytoremediation and natural attenuation, respectively. The sediments had silty texture and an average concentration of 5% organic matter (OM). Phytoremediation (60.76%) showed better efficiency in the remediation of the 16 PAHs compared to natural attenuation (49.57%). Principal component analyses showed a correlation between the concentrations of PAHs with pH, Eh, OM and DO in both experiments.

Gulls are generalist seabirds, increasingly drawn to urban environments where many species take advantage of abundant food sources, such as landfill sites. Despite this, data on items ingested at these locations, including human refuse, is limited. Here we investigate ingestion of prey and anthropogenic debris items in boluses (regurgitated pellets) from Pacific Gulls (Larus pacificus). A total of 374 boluses were collected between 2018 and 2020 in Tasmania. Debris was present in 92.51% of boluses (n = 346), with plastic (86.63%, n = 324) and glass (64.71%, n = 242) being the most prominent types. An abundance of intact, household items (e.g., dental floss, food wrappers) suggest the gulls regularly feed at landfill sites. In addition, the boluses are deposited at a roosting site located within an important wetland, thus we propose that the gulls may be functioning as a previously unrecognised vector of anthropogenic debris from urban centres to aquatic environments.

Meiofauna particularly marine nematodes around the Caiwei Guyot in the northwest Pacific Ocean and a Polymetallic Nodule Field in the northeast Pacific Ocean were studied. Due to the geographic structure, the Caiwei Guyot and the Polymetallic Nodule Field had different environmental characteristics. Meiofaunal abundances around the Guyot area ranged from 9.18 to 25.59 ind./10 cm², which were much lower than those in the Polymetallic Nodule Field. Marine nematode was the most dominant group. A total of 123 species, belonging to 74 genera and 29 families were found. Xyalidae (21.43%), Cyatholaimidae (9.82%), Linhomoeidae (8.03%) were the dominant families. The values of species number, Margalef's species richness and Shannon-Wiener diversity index ranged from 15 to 62, 4.75 to 12.84 and 2.58 to 3.93, respectively. The combination of water depth, silt-clay content and chlorophyll-a concentration can best explain the differences of nematode community. This study provides a baseline for deep-sea meiofauna distribution.