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Non-native Rhizophora mangle as sinks for coastal contamination on Moloka'i, Hawai'i
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Researchers studied microplastic and pesticide contamination in coastal areas of Moloka'i, Hawaii, comparing zones with invasive mangrove trees to open coastline. They found that mangrove roots concentrated both microplastics (up to 2,004 particles per kg) and the insecticide bifenthrin at high levels, acting as pollution sinks that could pose risks if these trees are removed.
Coastal mangrove forests provide a suite of important services, including sequestration of anthropogenic contamination. Yet, research lags on the environmental fate and potential human health risks of mangrove-sequestered contaminants in the context of mangrove removal for development and range shifts due to climate change. To address this, we conducted a study on Moloka'i, Hawai'i, comparing microplastic and pesticide contamination in coastal compartments both at areas modified by non-native mangroves and unmodified, open coastline. Sediment, porewater, and mangrove plant tissues were collected to quantify microplastic and pesticide concentrations across ecosystem type. Average microplastics were similar between mangrove (8.89 items/kg) and non-mangrove areas (9.01 items/kg) in sediment and porewater, but mangrove roots were a significant reservoir of microplastics (2004 items/kg). Additionally, there was a strong relationship between proximity to urban development and microplastics detected. Six pesticides were detected, most commonly the insecticide bifenthrin, found in most sediment samples (11.3 ng/g), all root samples (243.3 ng/g), and one propagule sample (8.60 ng/g). Other pesticides detected with appreciable concentrations include the neonicotinoid insecticide imidacloprid and the legacy insecticide transformation product, p,p’-DDE. The other detections, all at concentrations < 1 ng/g, were p,p’-DDT, trifluralin, and permethrin. The high concentrations of bifenthrin in roots compared to lower concentrations detected in sediment suggest that mangrove roots strongly accumulate some pesticides, indicating mangrove roots as a sink for organic contaminants. Future research should focus on expanding this work to other Hawai'ian Islands and other locations where mangroves have been introduced to further examine the observed trends. Researchers should also investigate the fate and cycling of pesticides and microplastics adhered to mangrove roots, which will better inform future non-native mangrove removal efforts on Moloka'i and elsewhere.
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Microplastics Presence in Rhizophora mangle Roots throughout Fishponds and Open Coasts in Moloka'i, Hawaii
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This study found microplastics in the roots of red mangrove trees at both fishpond and open coast sites in Hawaii, documenting plastic contamination in a critical coastal habitat. Mangrove ecosystems are important nursery habitats for fish and shellfish, so microplastic contamination there has broader food chain implications.
Accumulation of Plastics and Trace Elements in the Mangrove Forests of Bima City Bay, Indonesia
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Researchers investigated microplastic and trace element pollution in mangrove soils and plant tissues across areas with varying levels of human activity in Bima Bay, Indonesia. They found that microplastic levels were highest near hotels and lowest in rural areas, with plant tissues selectively accumulating certain polymer types like polyamides. The results highlight that mangrove forests act as sinks for plastic pollution, with contamination levels closely tied to local human activity.
Microplastic Contamination in Water, Sediment, and Biota in Mangrove Forests
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This review synthesized research on microplastic contamination in mangrove forest water, sediment, and biota, finding that mangroves act as both sinks and potential sources of microplastics due to their complex hydrodynamics, with ecotoxicological data on mangrove-specific organisms remaining limited.
Characterization, source, and retention of microplastic in sandy beaches and mangrove wetlands of the Qinzhou Bay, China
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Researchers characterized microplastics in sediments from both sandy beaches and mangrove wetlands in Qinzhou Bay, southern China, finding higher abundances in mangrove sediments than beach sediments due to the trapping function of root systems. The study demonstrates that mangroves act as effective sinks for microplastic pollution in coastal zones.
Evidence of elevated microplastic accumulation in Pacific Island mangrove sediments
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Researchers found that mangrove sediments in Fiji contained nearly ten times more microplastics than surrounding non-mangrove areas, with consistent results across both urban and rural sites. Fibers were the most common type of microplastic found, and the contamination levels were comparable to heavily polluted regions elsewhere in the world. The study highlights that mangroves, while vital coastal ecosystems, may be acting as significant traps for microplastic pollution in Pacific Island nations.
Research digests by email
When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.