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.
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.
Sci Total Environ. 2021 Jun 10;772:145520. doi: 10.1016/j.scitotenv.2021.145520. Epub 2021 Feb 2.
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.
近岸生物源栖息地已知会捕获沉积物，因此也可能积累生物污染的非浮性微塑料。我们使用产生电流的野外水槽（TiDyFLOW），通过三种对比的生物源栖息地：1）海草、2）大型藻类和 3）硬珊瑚，实验评估了两种粒径大小，即 0.5mm 和 2.5mm 的微塑料的捕获机制。结果表明，具有复杂结构和粗糙表面的底栖生物 - 如硬珊瑚 - 在其地上结构中捕获了最多的微塑料。然而，沉积物是微塑料的主要汇，积累的微塑料数量比底栖结构多 1 到 2 个数量级。沉积物中微塑料的积累可以用近床面湍流动能（TKE）来解释，表明这是由导致沉积物捕获的相同水动力过程控制的。因此，在保育和沿海保护服务方面最有价值的生物源栖息地，在其沉积物中积累微塑料的能力也最高。与 2.5mm 颗粒相比，0.5mm 颗粒在沉积物中的捕获量明显更大，因为特别是较小的微塑料被卷入沉积物中。目前的观察结果有助于解释为什么特别是小于 1mm 的微塑料在地表水层中缺失。
