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

Evaluating microplastic contamination in Omani mangrove habitats using large mud snails (Terebralia palustris)

This study investigated microplastic pollution in the large mud snail Terebralia palustris (Linnaeus, 1767) (Gastropoda: Potamididae) inhabiting the Avicennia marina mangrove ecosystems along the Sea of Oman. A modified digestion protocol, combining two methods, was employed to improve the detection of microplastics within the snail tissue. Results indicated that 50 % of the examined snails contained microplastics, with significant variability observed among different lagoons. Snails from the polluted Shinas lagoon exhibited higher levels of microplastics compared to those from the lowest polluted Al-Qurum Natural Reserve (MPA). The most prevalent type of microplastic in snail tissues was fibers, making up 75.7 % of the total. Fragments constituted about 24.2 %. Using portable Raman spectrometry, Polyurethane (PU) was identified as the predominant polymer, accounting for 50 % of the total. This was followed by Acrylic and Polyethylene, each representing 18.75 %, and Polyethylene Vynil Acetate (PEVA) at 12.50 %. Overall, it is clear that while snails do reflect the presence of microplastics (MPs) in their environment, their physical attributes do not strongly correlate with the levels or types of MPs they contain. Additionally, the significant difference between the abundance of MPs in sediment and in snails illustrates that, while snails may serve as general indicators of microplastic pollution, they may not be reliable as precise bioindicators or sentinel species for quantifying the extent of this pollution. Further studies are needed to explore other potential bioindicators in mangrove habitats.

Micro- and mesoplastic pollution in the surface water and nekton from the eastern Indian ocean: Spatiotemporal variation, correlation and risk assessment

The pollution of micro- and mesoplastic (MMP) in the Eastern Indian Ocean (EIO) remains poorly understood. The present study revealed that MMP abundance in nekton from EIO in 2022 (mean: 2.30 ± 0.39 items individual-1 and 1.81 ± 0.54 items g-1) was significantly higher than that in 2021 (mean: 1.60 ± 0.22 items individual-1 and 0.80 ± 0.13 items g-1). In contrast, MMP abundance in surface water varied insignificantly between 2021 (mean: 0.04 ± 0.01 items m-3) and 2022 (mean: 0.05 ± 0.02 items m-3). The rise in predominant polymers-polypropylene (PP), rayon (RA), and polyester (PES)-in nekton from 2021 to 2022 may suggest increased pollution from face masks and home textiles along coastal regions. Notable spatial variation in PP and RA between the northeastern and southeastern regions was observed only in nekton, suggesting they are better indicators of MMP spatiotemporal variation than surface water. Shadow driftfish ingested more MMPs than purpleback flying squid and mackerel scad, likely due to its deeper habitat. By simultaneously considering color, composition, and shape, integrated MMP analysis showed insignificant correlation between MMP pollution in surface water and nekton, suggesting that nekton may ingest MMPs through multiple pathways beyond surface water. Risk indices for surface water and nekton reached moderate to upper levels globally, emphasizing the need for continued monitoring in the EIO. Epoxy resin, rubber, and PP + acrylic were identified as the most hazardous polymers, providing a valuable basis for developing effective strategies to mitigate plastic pollution.

Mangrove mud clam as an effective sentinel species for monitoring changes in coastal microplastic pollution

The worldwide mangrove shorelines are experiencing considerable contamination from microplastics (MPs). Finding an effective sentinel species in the mangrove ecosystem is crucial for early warning of ecological and human health risks posed by coastal microplastic pollution. This study collected 186 specimens of the widely distributed mangrove clam (Geloina expansa, Solander, 1786) from 18 stations along the Leizhou Peninsula, the largest mangrove coast in Southern China. This study discovered that mangrove mud clams accumulated a relatively high abundance of MPs (2.96 [1.61 - 6.03] items·g-1) in their soft tissue, wet weight, as compared to previously reported levels in bivalves. MPs abundance is significantly (p < 0.05 or 0.0001) influenced by coastal urban development, aquaculture, and shell size. Furthermore, the aggregated MPs exhibit a significantly high polymer risk index (Level III, H = 353.83). The estimated annual intake risk (EAI) from resident consumption, as calculated via a specific questionnaire survey, was at a moderate level (990 - 2475, items·g -1·Capita -1). However, the EAI based on suggested nutritional standards is very high, reaching 113,990 (79,298 - 148,681), items·g -1·Capita -1. We recommend utilizing the mangrove mud clam as sentinel species for the monitoring of MPs pollution changing across global coastlines.

Prioritising plastic pollution research in blue carbon ecosystems: A scientometric overview

The Blue Carbon Ecosystems (BCEs), comprising mangroves, saltmarshes, and seagrasses, located at the land-ocean interface provide crucial ecosystem services. These ecosystems serve as a natural barrier against the transportation of plastic waste from land to the ocean, effectively intercepting and mitigating plastic pollution in the ocean. To gain insights into the current state of research, and uncover key research gaps related to plastic pollution in BCEs, this study conveyed a comprehensive overview using bibliometric, altmetric, and literature synthesis approaches. The bibliometric analysis revealed a significant increase in publications addressing plastic pollution in BCEs, particularly since 2018. Geographically, Chinese institutions have made substantial contributions to this research field compared to countries and regions with extensive BCEs and established blue carbon science programs. Furthermore, many studies have focused on mangrove ecosystems, while limited attention was given to exploring plastic pollution in saltmarsh, seagrass, and multiple ecosystems simultaneously. Through a systematic analysis, this study identified four major research themes in BCE-plastics research: a) plastic trapping by vegetated coastal ecosystems, b) microbial plastic degradation, c) ingestion of plastic by benthic organisms, and d) effects of plastic on blue carbon biogeochemistry. Upon synthesising the current knowledge in each theme, we employed a perspective lens to outline future research frameworks, specifically emphasising habitat characteristics and blue carbon biogeochemistry. Emphasising the importance of synergistic research between plastic pollution and blue carbon science, we underscore the opportunities to progress our understanding of plastic reservoirs across BCEs and their subsequent effects on blue carbon sequestration and mineralisation. Together, the outcomes of this review have overarching implications for managing plastic pollution and optimising climate mitigation outcomes through the blue carbon strategies.

Microplastic abundance in urban vs. peri-urban mangroves: The feasibility of using invertebrates as biomonitors of microplastic pollution in two mangrove dominated estuaries of southern Africa

Microplastic (MP) prevalence has been well documented, however, knowledge gaps exist for African mangrove forests. This research is the first to compare MP pollution (using FT-IR analysis) in an urban (Durban Bay) and peri-urban (Mngazana Estuary) mangrove forest in South Africa, across different compartments. MP pollution (typology, abundance, and distribution) was quantified in estuarine surface water, sediment and the soft tissue of three keystone species (Austruca occidentalis, Chiromantes eulimene and Cerithidea decollata) in relation to disturbances acting on these systems. MP averages ranged from 99 to 82 MPs/kg sediment, 177 to 76 MPs/L water and 82 to 59 MP/g-1 DW in biota. Overall fibres were the dominant MP type across all compartments. The three invertebrate species exhibited MP bioaccumulation, however, significant differences were observed between MP concentrations in the soft body tissue of invertebrates and abiotic compartments, providing evidence that they are not effective biomonitors of MP pollution.