Habitat-forming species trap microplastics into coastal sediment sinks

Jaco C de Smit; Andrea Anton; Cecilia Martin; Susann Rossbach; Tjeerd J Bouma; Carlos M Duarte

doi:10.1016/j.scitotenv.2021.145520

Habitat-forming species trap microplastics into coastal sediment sinks

Sci Total Environ. 2021 Jun 10:772:145520. doi: 10.1016/j.scitotenv.2021.145520. Epub 2021 Feb 2.

Authors

Jaco C de Smit¹, Andrea Anton², Cecilia Martin², Susann Rossbach², Tjeerd J Bouma³, Carlos M Duarte²

Affiliations

¹ NIOZ Royal Netherlands Institute for Sea Research, Department of Estuarine and Delta Systems, P.O. Box 140, 4400 AC Yerseke, the Netherlands; Faculty of Geosciences, Department of Physical Geography, Utrecht University, the Netherlands. Electronic address: jaco.de.smit@nioz.nl.
² Red Sea Research Center (RSRC), King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia; Computational Bioscience Research Center (CBRC), King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia.
³ NIOZ Royal Netherlands Institute for Sea Research, Department of Estuarine and Delta Systems, P.O. Box 140, 4400 AC Yerseke, the Netherlands; Faculty of Geosciences, Department of Physical Geography, Utrecht University, the Netherlands.

PMID: 33770872
DOI: 10.1016/j.scitotenv.2021.145520

Abstract

Nearshore biogenic habitats are known to trap sediments, and may therefore also accumulate biofouled, non-buoyant microplastics. Using a current-generating field flume (TiDyFLOW), we experimentally assessed the mechanisms of microplastic trapping of two size classes, 0.5 mm and 2.5 mm particle size, by three contrasting types of biogenic habitats: 1) seagrasses, 2) macroalgae, and 3) scleractinian corals. Results showed that benthic organisms with a complex architecture and rough surface - such as hard corals - trap the highest number of microplastics in their aboveground structure. Sediment was however the major microplastic sink, accumulating 1 to 2 orders of magnitude more microplastics than the benthic structure. Microplastic accumulation in the sediment could be explained by near-bed turbulent kinetic energy (TKE), indicating that this is governed by the same hydrodynamic processes leading to sediment trapping. Thus, the most valuable biogenic habitats in terms of nursery and coastal protection services also have the highest capacity of accumulating microplastics in their sediments. A significantly larger fraction of 0.5 mm particles was trapped in the sediment compared to 2.5 mm particles, because especially the smaller microplastics are entrained into the sediment. Present observations contribute to explaining why especially microplastics smaller than 1 mm are missing in surface waters.

Keywords: Benthic structures; Coastal ecosystems; Hydrodynamics; Plastic; Sediment.