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Canopy Accumulation: Are Seagrass Meadows a Sink of Microplastics?

Oceans 2021 58 citations

AI summary Read the abstract

This meta-analysis investigates whether seagrass meadows accumulate more microplastics than surrounding bare sediments. The findings show that while microplastics are nearly everywhere in coastal sediments, seagrass beds do not concentrate them at higher levels than other areas. However, the widespread contamination is still concerning because many fish species depend on seagrass habitats, creating a pathway for plastics to enter the food chain.

Study Type Review

A growing body of research is documenting the accumulation of microplastics within marine sediments around the world. The hydrodynamic influences of seagrasses in coastal environments are shown to increase sedimentation of finer particles and as a result there has been speculation that this attribute will lead to seagrass meadows acting as a site of elevated microplastic contamination. To date a range of localised studies have provided conflicting answers to this hypothesis. Seagrass meadows provide multiple ecosystem services including vital support roles for a range of fisheries; therefore, there are considerable human health implications for understanding their role as sinks of microplastics. This research investigated the abundance and diversity of microplastics present in temperate North Atlantic seagrass meadow sediments relative to unvegetated sediments and examined how they correlate with the meadow structure and the sediment type. We also placed this data in the context of the current knowledge of microplastics in seagrass sediments through a global meta-analysis of published data. Eight seagrass meadows and adjacent unvegetated sites around the UK were sampled to test for the abundance of microplastic particles in the sediment. Microplastics were found in 98% of the samples, with fibres making up 91.8% of all microplastics identified. Abundance was recorded to overall be 215 ± 163 microplastic particles (MP) kg−1 Dry Weight (DW) of sediment in seagrass and 221 ± 236 MP kg−1 DW of sediment in unvegetated habitats. There were no significant differences found between the number of MP with respect to vegetation. We report evidence of the almost ubiquitous contamination of seagrass sediments with microplastics both in the UK and globally but find that the contamination reflects a general build-up of microplastics in the wider environment rather than becoming concentrated within seagrass as an enhanced sink. Microplastic build up in sediments is hypothesised to be the result of local hydrodynamics and plastic sources rather than the result of elevated habitat level concentration. Although not of a higher abundance in seagrass, such contamination in seagrass is of cause for concern given the high dependency of many species of fish on these habitat types and the potential for plastics to move up the food chain.

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This systematic review of 84 studies finds that seagrass meadows act as natural traps for microplastics, accumulating higher concentrations in their sediments than surrounding areas. While this filtering role may protect open waters, it also means these important coastal ecosystems are bearing a disproportionate burden of plastic pollution.

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A critical synthesis of seagrass meadows as microplastic sinks: Current trends and research gaps

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This systematic review of 84 studies finds that seagrass meadows act as natural traps for microplastics, accumulating higher concentrations in their sediments than surrounding areas. While this filtering role may protect open waters, it raises concerns about the long-term health of these vital coastal ecosystems.

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Seagrass beds in coastal waters were found to trap and accumulate microplastics at higher concentrations than surrounding unvegetated sediments, acting as effective sinks for plastic particles due to their dense canopy structure. This positions seagrass meadows as emerging hotspots of microplastic contamination in coastal ecosystems.

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