Reef‐building corals act as long‐term sink for microplastic. (28th October 2021)

• Record Type: Journal Article
• Authors: Reichert, Jessica; Arnold, Angelina L.; Hammer, Nils; Miller, Ingo B.; Rades, Marvin; Schubert, Patrick; Ziegler, Maren; Wilke, Thomas
• Is Part Of: Global change biology. Volume 28:Number 1(2022)
• Page Start: 33
• Page End: 45
• Publication Date: 2021-10-28
• Subjects: coral skeleton -- long‐term experiment -- marine microplastic -- missing plastic phenomenon -- particle uptake -- plastic sink in the ocean -- reef‐building corals; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15920
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: The pollution of the marine environment with microplastics is pervasive. However, microplastic concentrations in the seawater are lower than the number of particles entering the oceans, suggesting that plastic particles accumulate in environmental sinks. Yet, the exact long‐term sinks related to the "missing plastic" phenomenon are barely explored. Sediments in nearshore biogenic habitats are known to trap large amounts of microplastics, but also the three‐dimensional structures of coral reefs might serve as unique, living long‐term sinks. The main framework builders, reef‐building corals, have been shown to ingest and overgrow microplastics, potentially leading to a deposition of particles in reef structures. However, little is known about the number of deposited particles and the underlying processes determining the permanent deposition in the coral skeletons. To test whether corals may act as living long‐term sink for microplastic, we exposed four reef‐building coral species to polyethylene microplastics (200 particles L −1 ) in an 18‐month laboratory experiment. We found microplastics in all treatment specimens, with low numbers of particles trapped in the coral tissue (up to 2 particles per cm 2 ) and much higher numbers in the skeleton (up to 84 particles per cm 3 ). The numbers of particles accumulated in the coral skeletons were mainly related to coral growth (i.e., skeletal growth in volume), suggesting that deposition is a regularly occurring stochastic process. We estimate that reef‐building corals may remove 0.09%–2.82% of the bioavailable microplastics from tropical shallow‐reef waters per year. Our study shows for the first time that microplastic particles accumulate permanently in a biological sink, helping to explain the "missing plastic" phenomenon. This highlights the importance of coral reefs for the ecological balance of the oceans and reinforces the need to protect them, not only to mitigate the effects of climate change but also to preserve their ecosystem services as long‐term sink for microplastic. Abstract : To investigate whether tropical shallow‐water reef‐building corals can act as long‐term sinks for microplastics, we exposed four common reef‐building coral species to polyethylene microplastics for 18 months in a microcosm experiment. We found that reef‐building corals permanently incorporate microplastics into their skeletons, acting as unique biological sink for microplastics. We estimate that tropical reef‐building corals worldwide can accumulate ~1% of the particles present in tropical reef waters annually and represent a previously unknown link in the "missing plastic" phenomenon.