Department of Geology, Faculty of Physical Sciences, University of Nigeria, Nsukka, 410001, Nigeria.
School of Ocean and Earth Science, National Oceanography Centre (Southampton), University of Southampton, Southampton, SO14 3ZH, UK.
Sci Rep. 2022 Sep 15;12(1):15546. doi: 10.1038/s41598-022-18881-7.
Saltmarshes are important natural ecosystems along many temperate (and other) coastlines. They stabilize sediments and act as biofilters for a range of industrial pollutants and, potentially, microplastics. Accumulation of microplastics along estuarine coastlines may be enhanced by the presence of saltmarsh species, as they offer better particle trapping efficiency than adjacent intertidal mudflats under prevailing flood and ebb tidal currents. However, the trapping efficiency of entire saltmarsh systems under varying flow conditions has not been widely assessed. While the effects of saltmarsh systems on water flow, and on sediment transport and trapping, have been relatively well studied, little is known about the contributions of saltmarsh halophytes, resident organisms and the associated saltmarsh sediments to the trapping of microplastics. To address this, a series of flume experiments were undertaken to examine transport and accumulation of Bakelite particles (~ 500 µm) and PVC nurdles (~ 5 mm) as model plastics in sub-sampled saltmarsh and intertidal mudflat monoliths. The results showed that saltmarsh systems influenced the hydrodynamics within and above the canopy, enhancing turbulence and shear stresses. With increasing flow velocities (≤ 0.51 m s), negligible quantities (2 [Formula: see text] 10 mg L) of sediments and Bakelite particles were eroded and resuspended. The algal biogenic roughness from the mudflat, and the vegetative roughness from the Spartina plants on the saltmarsh, inhibited the transportation of the microplastics within the tested systems. Resident burrowing crabs (Carcinus maenas) promoted the burial, release and transport of microplastics. The results of this study provide evidence of the contributory roles of saltmarsh systems in the sequestration of microplastics and sediment stabilization. Estuarine saltmarsh systems can act as sinks for microplastics with enhanced burial from burrowing crabs under favourable flow conditions.
盐沼是许多温带（和其他）海岸线重要的自然生态系统。它们稳定沉积物并充当多种工业污染物和潜在微塑料的生物过滤器。由于盐沼物种的存在，微塑料在河口海岸线上的积累可能会增加，因为它们在盛行的涨潮和退潮潮流下提供比相邻潮间泥滩更高的颗粒捕集效率。然而，在不同的水流条件下，整个盐沼系统的捕集效率尚未得到广泛评估。虽然盐沼系统对水流以及泥沙输运和捕集的影响已经得到了相对较好的研究，但对于盐沼盐生植物、栖息生物和相关盐沼沉积物对微塑料捕集的贡献知之甚少。为了解决这个问题，进行了一系列水槽实验，以检查 Bakelite 颗粒（500μm）和 PVC 小球（5mm）作为模型塑料在亚采样盐沼和潮间泥滩单体中的输运和积累。结果表明，盐沼系统影响冠层内和冠层上方的水动力，增强了湍流和剪切应力。随着流速的增加（≤0.51m s），几乎没有数量（2 [Formula: see text] 10mg L）的沉积物和 Bakelite 颗粒被侵蚀和再悬浮。来自泥滩的藻类生物粗糙度和盐沼中 Spartina 植物的植物粗糙度抑制了微塑料在测试系统中的运输。栖息的掘洞蟹（Carcinus maenas）促进了微塑料的埋藏、释放和运输。本研究结果提供了盐沼系统在微塑料和沉积物稳定封存中的贡献作用的证据。在有利的水流条件下，掘洞蟹增强了微塑料的埋藏作用，河口盐沼系统可以成为微塑料的汇。
