Many typical neuston trawls can only be used during relatively calm sea states and slow tow speeds. During two expeditions to the Bay of Bengal and the eastern South Pacific we investigated whether the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collects similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the DiSalvo neuston net. Using a 335 μm net, the AVANI trawl can collect microplastics from the sea surface at speeds up to 8 knots as it “skis” across the surface, whereas the manta and DiSalvo neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. Generally, the AVANI trawl collected a greater numerical abundance and weight of plastic particles in most size classes and debris types than the manta trawl and DiSalvo neuston net, likely because these trawls only skim the surface layer while the AVANI trawl, moving vertically in a random fashion, collects a “deeper” sample, capturing the few plastics that float slightly lower in the water column. However, the samples did not differ enough that results were significantly affected, suggesting that studies done with these different trawls are comparable. The advantage of the AVANI trawl over traditional research trawls is that it allows for collection on vessels underway at high speeds and during long transits, allowing for a nearly continuous sampling effort over long distances. As local surface currents make sea surface abundance widely heterogeneous, widely spaced short-tow trawls, such as the manta and DiSalvo trawls, can catch or miss hotspots or meso-scale variability of microplastic accumulations, whereas the AVANI trawl, if utilized for back-to-back tows of intermediate distances (5–10 km), can bridge variable wind conditions and debris concentrations potentially reducing variance and provide a greater resolution of spatial distribution.

Plastic pollution is ubiquitous and not even remote protected islands are safe from it. Floating debris can adsorb toxic compounds that concentrate on their surface, being available to the animals that ingest them. For this reason, a baseline study of plastic pollution was conducted in the remote Revillagigedo Archipelago, in the Mexican Pacific Ocean. In 47 manta net samples an average of 4.8 plastics/1000m² was found, 73% of the pieces being <5 mm. Polyethylene and polypropylene were the most common polymers found. The chemical analysis of organic pollutants revealed that organochlorine pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls are adsorbed on the plastics collected in the area. Filter feeding megafauna such as humpback whales, manta rays and whale sharks could ingest contaminated micro and macroplastics. Plastics were found also on the beach, where they are available to the ingestion by terrestrial animals, including endemic species endangered to extinction.

This study comprises the first record of a juvenile Giant Devil Ray specimen for Rio de Janeiro, Southeastern Brazil, and its metal and metalloid contents. A scientometric assessment was also performed for the Manta and Mobula genera. Only five records were found, and only As, Cd, Pb, Hg, Pt, Pd and Rh have been assessed. All studies but one concerned human consumption. A significant knowledge gap on metal and metalloid ecotoxicology for mobulid rays is noted, indicating the emergence of a new field of research that th may be applied for wildlife conservation and management in response to anthropogenic contamination. Our study is also the first to provide Al, Cr, Cu, Fe, Mn, Sr, Ti, V and Zn contents for muscle, liver, brain and kidney for a mobulid ray and one of the scarce reports concerning As, Cd, Hg and Pb in muscle, liver and kidney.

Plastics in marine environments vary in their physical and chemical properties, influencing their risk to biota once ingested. Manta rays are large filter-feeders that ingest plastics. To assess this risk, we characterized the plastics in a critical feeding habitat off Nusa Penida, Indonesia. We examined the color and polymer composition of sampled small-sized plastics (<30 mm). Plastics were mostly secondary microplastics and transparent (46%), white/off-white (24%), and blue/green (22%). Fourier transform infrared spectroscopy of plastics grouped according to type (films, fragments, foam, or lines) and color indicated that most plastics were polyethylene (PE) or polypropylene (PP) (99%), with the remainder polystyrene and polyester. Visual characterization aligned with single polymer composition in seven out of ten groups. Although PE and PP have relatively low toxicity compared to other plastics, their composing monomers and associated pollutants and microbes are of concern to manta rays and other marine biota.

Two methods for marine microlitter sampling were compared in the Gulf of Finland, northern Baltic Sea: manta trawl (333μm) and a submersible pump (300 or 100μm). Concentrations of microlitter (microplastics, combustion particles, non-synthetic fibres) in the samples collected with both methods and filter sizes remained <10particlesm−3. The pump with 100μm filter gave higher microlitter concentrations compared to manta trawl or pump with 300μm filter. Manta sampling covers larger areas, but is potentially subjected to contamination during sample processing and does not give precise volumetric values. Using a submerged pump allows method controls, use of different filter sizes and gives exact volumetric measures. Both devices need relatively calm weather for operation. The choice of the method in general depends on the aim of the study. For monitoring environmentally relevant size fractions of microlitter the use of 100μm or smaller mesh size is recommended for the Baltic Sea.

Mobulid rays are targeted in fisheries for their branchial plates, for use in Chinese medicine. Branchial plate and muscle tissue from Mobula japanica were collected from fish markets in Sri Lanka, and muscle tissue biopsies from Manta alfredi in Australia. These were analysed for arsenic, cadmium, lead and mercury and compared to maximum levels (MLs) set by Food Standards Australia and New Zealand (FSANZ), European Commission (EC) and Codex Alimentarius Commission. The estimated intake for a vulnerable human age group was compared to minimal risk levels set by the Agency for Toxic Substances and Disease Registry. The mean inorganic arsenic concentration in M. japanica muscle was equivalent to the FSANZ ML while cadmium exceeded the EC ML. The mean concentration of lead in M. alfredi muscle tissue exceeded EC and Codex MLs. There were significant positive linear correlations between branchial plate and muscle tissue concentrations for arsenic, cadmium and lead.

High spatial resolution WorldView-2 (WV2) satellite imagery coupled with field observations have been utilized for mapping the coral reefs around Hendorabi Island in the northern Persian Gulf. In doing so, three standard multispectral bands (red, green, and blue) were selected to produce a classified map for benthic habitats. The in-situ observations were included photo-transects taken by snorkeling in water surface and manta tow technique. The satellite image has been classified using support vector machine (SVM) classifier by considering the information obtained from field measurements as both training and control points data. The results obtained from manta tow demonstrated that the mean total live hard coral coverage was 29.04% ± 2.44% around the island. Massive corals poritiids (20.70%) and branching corals acroporiids (20.33%) showed higher live coral coverage compared to other corals. Moreover, the map produced from satellite image illustrated the distribution of habitats with 78.1% of overall accuracy.

The transport sector is recognized as one of the largest carbon emitters. To achieve China’s carbon peak commitment in the Paris Agreement on schedule, it is indispensable to explore the peak carbon emissions and mitigation strategies in the transport sector. Many researches in the past have contextualized in China’s total emissions peak, while the study about forecasting China’s transport CO₂ emissions peak seldom appeared, especially the application of intelligent prediction model. To further investigate the determinants and forecast the peak of transport CO₂ emissions in China accurately, a novel bio-inspired prediction model is proposed in this paper, namely, the extreme learning machine (ELM) optimized by manta rays foraging optimization (MRFO), hereafter referred as MRFO-ELM. Adhering to this hybrid model, the mean impact value (MIV) method is then employed to evaluate and differentiate the importance of thirteen influencing factors. Additionally, three scenarios are set to conduct prediction of China’s transport CO₂ emissions. The empirical results indicate that the proposed MRFO-ELM has excellent performance in terms of the optimization searching velocity and prediction accuracy. Simultaneously the level of vehicle electrification is verified to be one of the emerging major factors affecting China’s transport CO₂ emissions. The transport CO₂ emissions in China would peak in 2039 under the baseline model scenario, while the plateau would occur in 2035 or 2043 under sustainable development mode and high growth mode, respectively. The peak years imply much pressure on China’s transport carbon emissions abatement currently, whereas active policy adjustments can effectively urge the earlier occurrence of the emission peak. These new findings suggest that it is essential for China to improve the energy mix and encourage the electric energy replacement in line with urbanization pace, so as to achieve CO₂ emissions mitigation in the transport industry.

An increasing number of reports have been published concerning microplastic (MP) pollution in aquatic environments. Methods used in these studies continue to be updated and lack standardization, so that an up-to-date review pertaining methods for MP research is needed. This critical review examines the analytical methods, including sampling, identification, and quantitation, for MP research. Samples are generally collected from water, sediment, and biota gastrointestinal tract. Manta nets or trawls are prevalently used in surface water sampling, while direct shoveling or box-corer grab are commonly applied in sediment sampling. Microplastics in biota are generally obtained by dissecting organisms and separating livers, gills, and guts. Density separation is frequently chosen to separate MPs from sample matrices. Chemical digestion can dissolve other organic materials and isolate MPs for further identification. Visual sorting should be combined with chemical composition analysis to better identify the polymer type. Pyrolysis or thermal decomposition gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopy, and Raman spectroscopy are currently the main technologies for MP identification. Units prevalently used to express MP abundance in water, sediment, and biota are “particles per m³,” “particles per m²,” and “particles per individual,” respectively. As MP abundances often varied with the methods used, we recommend that analytical protocols of MPs should better be standardized and optimized. Despite the important progress in analysis of MPs, detection technologies for identifying nano-sized plastic particles are still lacking, and therefore should be developed swiftly.