The seasonal cycle of micro and meso-plastics in surface waters in a coastal environment (Ría de Vigo, NW Spain)

First multi-compartment approach to microplastics in an urbanized estuary of Argentina: The case of Magallana gigas

This study assesses MP in water, sediment, gills, and digestive tract of the oyster Magallana gigas in three Bahía Blanca estuary sites, Argentina, using, Pollution Load Index (PLI) and SEM/EDX (Scanning Electron Microscopy with Energy-dispersive X-ray spectroscopy) and FTIR (Fourier-transform infrared spectroscopy) techniques. A total of 51 MPs were detected in water (mean: 16 items L-1) and 126 in sediments (mean: 1399 items Kg-1) with no significant differences between sites. In oysters, 186 MPs were found, with no significant differences in the MPs load between gills (mean: 2.41 items g-1 w.w), digestive tract (2.06 ± 2 items g-1 w.w), and the total tissues. Transparent fiber MPs were predominant, with cellulose, polyamides, polyethylene terephthalate and polyethylene being common polymers. SEM/EDX showed Si, Fe, Cl, Na, Ti, Al, K, Ca and suspended particulate matter on MP surfaces. The PLI indicated a low-risk level for estuary bivalves and water, suggesting minimal MPs impact.

Comparison of concentration, shape, and polymer composition between microplastics and mesoplastics in Japanese river waters

While plastics are classified by size as microplastics (<5 mm), mesoplastics (5-25 mm), and macroplastics (>25 mm), research in rivers has centered on microplastics, followed by macroplastics, with limited research on mesoplastics (research gap). This study aims to clarify the concentration, shape, and polymer composition of microplastics and mesoplastics in Japanese river water. We conducted field surveys for microplastics and mesoplastics in 147 rivers and at 185 measurement stations. The novelty of this study is in the use of a large number of field data to minimize the effect of the spatial difference in the microplastics and mesoplastics on the data analysis. Microplastics and mesoplastics were found at 183 (99 %) and 136 (74 %) stations, respectively. The difference between the concentration of microplastics and mesoplastics increased significantly with the increase in the concentration of microplastics, showing that the concentration of both microplastics and mesoplastics should be monitored to prevent an underestimation of plastic pollution in rivers with the appropriate sampling. A 2-stage size classification with microplastics (<5 mm) and macroplastics (>5 mm) is not suitable because the mesoplastics may be substantially overlooked. The regression slopes between microplastics and mesoplastics concentrations significant decrease in variance with increasing data number, suggesting the necessity of the large number of samples used in this study. The predominant shapes and polymer types of microplastics and mesoplastics were found to be fragment and fiber and polyethylene and polyethylene terephthalate (PET), respectively, which were affected appreciably by many fiber clusters. The fiber and PET ratios were dominant at stations with small population densities and urban ratios and can be attributed to atmospheric deposition and the underdeveloped rate of wastewater treatment plants (WWTPs). Therefore, it is necessary to monitor the dynamics and fate of fiber clusters inside and outside the basin.

Comparison of macroplastics dynamic across a tidal-dominated coastal habitat seascape including seagrasses, salt marshes, rocky bottoms and soft sediments

Coastal environments are usually composed by heterogeneous coastal-seascape, which can modify macroplastics accumulation dynamic. We evaluated seasonally the litter trapped on tidal-dominated habitats including two seagrass species, salt marsh, sandy beach, bare sediment and rocky bottom. Vegetated habitats showed the highest plastic accumulation in autumn-winter seasons, especially in medium-lower tidal-elevation zones. Seagrasses accumulated most of the degraded macroplastics, whereas averaged smaller sizes of litter were found in the salt marsh. The trapping ability of macrophytes was related to aboveground-biomass properties (i.e., height, width or flexibility) rather than shoot-density. Sandy beaches exhibited the highest plastics accumulation matching with the touristic-peak in the area, whereas rocky bottom was an important sink for macroplastics. This study provides authorities with comprehensible information to address the marine plastic litter problem taking into account the habitat-connectivity, the litter trap-ability of macrophytes and the tidal-elevation influence in order to improve future actions to deal with plastic pollution.

Microplastics in feces and pellets from yellow-legged gull (Larus michahellis) in the Atlantic Islands National Park of Galicia (NW Spain)

The Atlantic Islands National Park (AINP) in Galicia (NW of Spain) are host to large colonies of yellow-legged gulls (Larus michahellis). Here, we aimed to provide baseline data for the presence of microplastics (MP) in feces and pellets regurgitated of these resident yellow-legged gulls within this unique ecosystem. MP particles found in the samples were of five shapes (fiber, fragment, foam, film and rubber) and the predominant color was blue. The main plastic polymers identified by Raman spectroscopy were polypropylene and cellulose. The average size of the MP particles in the regurgitations was larger than that in the feces. Considering the population of Larus michahellis in the AINP, our estimates suggested an annual deposition of approximately 32.2 million of MP particles from feces and regurgitated pellets in the area.

First evidence of meso- and microplastics on the mangrove leaves ingested by herbivorous snails and induced transcriptional responses

Although evidence suggests the ubiquity of meso- and microplastics (MMPs) in mangrove forests, our knowledge of their bioavailability and risk on mangrove leaves is scarce. Here, we investigated MMP contamination concerning submerged mangrove leaves and herbivorous snails that mainly feed on them from the four mangrove forests located in Beibu Gulf, Guangxi Province, China. Results showed that the MMP abundance on the mangrove leaves ranged from 0.01 ± 0.00 to 0.42 ± 0.15 items cm^-2, while it ranged from 0.33 ± 0.21 to 6.20 ± 2.91 items individual^-1 in the snails. There were significant positive correlations between snails and leaves regarding the abundance of total MMPs and the proportions of MMPs with the same characteristics. Expanded polystyrene (EPS) that mainly derived from aquaculture rafts, accounted for a major component both on the leaves and in the snails in Shi Jiao (SJ). Both the detection frequency and percentage of larger EPS (2.00-17.50 mm) on the leaves in SJ were higher than other sites. Meanwhile, the detection frequency, abundance and percentage of larger EPS on the leaves had significant positive correlations with those of micro-EPS in the snails. These findings suggested that mangrove leaves may represent a viable pathway for MMPs to enter the herbivorous snails. Larger EPS with higher frequency of occurrence on mangrove leaves were more likely to be encountered and ingested by snail considering its opportunistic feeding behavior. In addition, 11 sensitive genes involved in the processes of metabolism, intestinal mucosal immune systems, and cellular transduction in the snails were significantly suppressed by MMP exposure, which may be potentially used as early biomarkers to indicate the biological effects of MMPs under realistic environmental conditions. Overall, this study provides novel insights into the fate, sources, and biological effects of MMPs on mangrove leaves.

Development of an analytical procedure to analyze microplastics in edible macroalgae using an enzymatic-oxidative digestion

Besides being food and a refuge to marine species, macroalgae are a powerful and renewable economic resource. However, they may introduce microplastics (MPs) in the trophic chain. We developed a reliable analytical method to characterize and quantify MPs in common and edible macroalgae. Several digestion methods and filters, along with various measurement options, were studied. A new enzymatic-oxidative protocol with a unique final filtration was selected and validated with a mixture of 5 commercial macroalgae (Undaria pinnatifida spp, Porphyra spp, Ulva spp, Laminaria ochroleuca and Himanthalia elongate). Further, it was shown that washing the macroalgae to release MPs is suboptimal and the potential adhesion of MPs to macroalgae was evaluated. A filter subsampling strategy that scans 33.64 % of its surface reduced the time required to characterize <70 μm particles and fibres directly on the 47 mm diameter filter using an IR microscope (1 sample/day).

Tracking synthetic microdebris contamination in a highly urbanized estuary through crabs as sentinel species: An ecological trait-based approach

Synthetic microdebris (particles of <5 mm) are a worldwide concern because they can affect the community structure of the aquatic ecosystems, organisms, and even food webs. For the biomonitoring of synthetic microdebris (especially microplastics, MPs), mainly benthic invertebrates are used, but crabs have been less studied in the literature. We studied the synthetic microdebris contamination in water, sediments, and three representative intertidal crabs (Neohelice granulata, Cyrtograpsus angulatus and Leptuca uruguayensis) with different lifestyles from the Bahía Blanca estuary, Argentina. The results obtained show the presence of cotton-polyamide (PA), polyethylene (PE), and polyethylene terephthalate (PET) in surface waters. In sediments, we identified cellulose modified (CE), polyester (PES), polyethylene (PE), and alkyd resin, while in crabs, cotton-PA and CE were the predominant ones. The MPs abundance ranged from 8 to 68 items L^-1 in surface water, from 971 to 2840 items Kg^-1 in sediments, and from 0 to 2.58 items g^-1 ww for the three species of crabs. Besides, paint sheets ranged from 0 to 17 in the total samples, with Cr, Mo, Ti, Pb, Cu, Al, S, Ba and Fe on their surface. There were significant differences between the microdebris abundances in the abiotic matrices but not among crabs species. The ecological traits of the different crabs helped to understand the accumulation of synthetic microdebris, an important characteristic when determining the choice of a good biomonitor.

The coastal waters of the south-east Bay of Biscay a dead-end for neustonic plastics

Numerical models point to the south-east Bay of Biscay as a convergence area for floating particles, including plastics. The few existing studies on plastic abundance in the area mainly focus on open waters and yet information on the coastal area is limited. To fill this gap, neustonic samples were taken along the coastal waters of the south-east Bay of Biscay (2017-2020) to define the spatial distribution of plastic abundances and composition. Results show an average plastic abundance of 739,395 ± 2,625,271 items/km² (998 ± 4338 g/km²). French waters were more affected, with five times higher plastic abundances than Spanish coasts. Microplastics represented 93 % of the total abundance of plastic items (28 % in weight), mesoplastics 7 % (26 %) and macroplastics 1 % (46 %). This study demonstrates that this area is a hotspot for plastic with levels in coastal waters similar to those in the Mediterranean Sea or other litter aggregation areas.