ORCID

Abstract

Coastal ecosystems, such as coral reefs, are vulnerable to microplastic pollution input from proximal riverine and shoreline sources. However, deposition, retention, and transport processes are largely unevaluated, especially in relation to hydrodynamics. For the first time, we experimentally investigate the retention of biofilmed microplastic by branching 3D printed corals (staghorn coral Acropora genus) under various unidirectional flows (U = {0.15, 0.20, 0.25, 0.30} ms −1) and canopy densities (15 and 48 corals m −2). These variables are found to drive trapping efficiency, with 79–98% of microplastics retained in coral canopies across the experimental duration at high flow velocities (U = 0.25–0.30 ms −1), compared to 10–13% for the bare bed, with denser canopies retaining only 15% more microplastics than the sparse canopy at highest flow conditions (U = 0.30 ms −1). Three fundamental trapping mechanisms were identified: (a) particle interception, (b) settlement on branches or within coral, and (c) accumulation in the downstream wake region of the coral. Corresponding hydrodynamics reveal that microplastic retention and spatial distribution is modulated by the energy-dissipative effects of corals due to flow-structure interactions reducing in-canopy velocities and generating localised turbulence. The wider ecological implications for coral systems are discussed in light of the findings, particularly in terms of concentrations and locations of plastic accumulation.

DOI

10.1016/j.envpol.2023.123094

Publication Date

2024-02-01

Publication Title

Environ Pollut

Volume

342

ISSN

0269-7491

Keywords

Coastal ecosystems, Hydrodynamics, Marine canopies, Microplastics, Particle trapping, Animals, Ecosystem, Anthozoa, Plastics, Coral Reefs

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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