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Transport and trapping in complex aquatic canopies: how do coral reefs act as sinks for microplastics?
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Researchers investigated how coral reef canopy structures act as sinks for microplastic particles by modifying turbulence, flow, and depositional processes in coastal zones, examining physical trapping mechanisms alongside biological incorporation within coral tissue and skeletons. The study addressed the 'missing plastic' problem by exploring whether the complex three-dimensional structure of shallow reefs intercepts microplastics transported from terrestrial sources before they reach open ocean.
The “missing plastic” phenomenon remains, whereby the transport and ultimate fate of microplastics in aquatic environments is mostly unknown. Marine plastic pollution mainly originates from terrestrial sources and upon reaching coastal zones interacts with nearshore ecosystems. Coral reefs in coastal areas are likely exposed to microplastics, especially shallow reefs at low tides, yet the interactions between microplastics and corals are largely unexplored. Reefs can form extremely complex canopies that can trap sediment, and likely act as a sink for microplastic pollution through serval ways: acting as a physical barrier, modifying turbulence and depositional processes, or through incorporation within coral tissue and skeletons. Given reefs form the foundation of highly biodiverse ecosystems, the entrapment of microplastics by coral would possibly increase ingestion by, and physiological damage to, corals and other reef organisms. The broader ecological impact may be considerable, as well as the repercussions for associated ecosystems services for hundreds of millions of people. Furthermore, the impacts of climate change and rising sea temperatures may be accentuated. Despite the growing concern of these consequences and field measurements revealing accumulation in a variety of aquatic canopies, the transport and dispositional processes that drive microplastic trapping in coral canopies is barely understood.Here, we investigated for the first time the prevalence of microplastic retention by branching coral canopies in a hydraulic flume under several unidirectional flow conditions. Coral colonies were created using 3D-printed models of staghorn coral, Acropora genus, an important reef building species found globally. A set weight of microplastics (biofilmed ground melamine, density 1.6 g/cm³) was released into canopies that represented recovering and healthy reefs to determine entrapment efficiency. Overhead and side cameras tracked microplastic distribution and trapping mechanisms. Furthermore, complimentary flow velocity profiles were acquired to understand the relationships between the canopy hydrodynamics and microplastic distribution. Our results provide an insight into microplastic transport dynamics and entrapment mechanisms within coral canopies. Results show that even sparse reefs may be vulnerable to notable microplastic trapping. The results provide insight that support the conjecture that canopies may act as a global sink for microplastic pollution. Further investigation is required in the exposure of these ecosystems to microplastics and impacts on the wider ecological system health, function, and potential subsequent transfer through food webs.
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Microplastic trapping efficiency and hydrodynamics in model coral reefs: A physical experimental investigation
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Researchers experimentally investigated how branching coral structures trap microplastics under different water flow speeds and canopy densities using 3D-printed model coral reefs. They found that coral canopies retained 79-98% of microplastics at higher flow velocities, compared to only 10-13% for bare surfaces, through mechanisms including particle interception and settlement on branches. The study suggests that coral reefs may act as significant accumulators of microplastic pollution, with implications for reef ecosystem health.
Reef‐building corals act as long‐term sink for microplastic
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Coral reef structures were shown to act as long-term sinks for microplastics, with microplastics accumulating in reef framework interstices and sediments at higher concentrations than surrounding seawater, potentially contributing to the resolution of the missing plastic problem in ocean budgets.
Do coral reefs act as sinks for microplastics?
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This review examined whether coral reefs act as sinks for microplastics, finding five mechanisms that promote microplastic accumulation including adhesion to corals, ingestion by reef organisms, trapping by reef structures, and burial in reef sediments. Despite covering less than 1% of ocean area, coral reefs disproportionately concentrate microplastics.
Transport and trapping of microplastics in coral reefs: a physical experimental investigation
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Researchers conducted physical experiments in a laboratory channel to study how microplastics are transported and trapped in simulated coral reef structures. Rough reef surfaces increased particle capture compared to flat beds. These findings help explain why coral reefs accumulate microplastics and inform predictions of plastic pollution impacts on biodiverse reef ecosystems.
Exploring Microplastic Interactions with Reef-Building Corals Across Flow Conditions
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Researchers examined how reef-building corals interact with microplastics under varying flow conditions, investigating whether active ingestion or passive adhesion dominates microplastic removal and which particle types and sizes are most readily captured by coral structures.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.