Fate of river-derived microplastics from the South China Sea: Sources to surrounding seas, shores, and abysses

Matsushita, Kosei; Uchiyama, Yusuke; Takaura, Naru; Kosako, Taichi

doi:10.1016/j.envpol.2022.119631

Cited by 9 publications

(4 citation statements)

References 69 publications

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“…In this high‐latitude region, the East Greenland Coastal Current interacts with the widely turning coast at Cape Farewell (Bacon et al., 2002; Sutherland & Pickart, 2008). Other global examples of plumes interacting with coastal corners are the Western Iberian plume at Cape Finisterre (Alvarez et al., 2011; Otero et al., 2008, 2009), the Mekong plume at Ca Mau Cape during the winter monsoon (e.g., Matsushita et al., 2022; Nguyen et al., 2022; Zeng et al., 2022), and the Ayeyarwady (Irrawaddy) plume at Mawtin Point (Liu et al., 2020; Sandeep & Pant, 2019). There are other pronounced coastal orientation changes near major rivers such as the Ob, Yenisei, and Yukon that influence wind response and plume behavior (Clark & Mannino, 2022; Frey & Osadchiev, 2021; Osadchiev et al., 2017).…”

Section: Discussionmentioning

confidence: 99%

Wind‐Enhanced Separation of Large‐Scale River Plumes From Coastal Corners

Whitney

2024

JGR Oceans

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Idealized models are analyzed to quantify how large‐scale river plumes interact with coastal corners with and without wind‐driven currents. The configuration has a corner formed by two perpendicular shelves (with constant slope) that are joined with a coastal radius of curvature (rc). The buoyant plume originates from an upstream point source. The rc and wind forcing are varied among runs. Steep‐ and gentle‐slope runs are compared for some situations. Without winds, plumes separate from corners with rc smaller than two inertial radii (ri); this threshold is twice the rc < ri theoretical separation criterion. After separation, no‐wind plumes form an anticyclonic bulge, and reattach farther downstream. Offshore excursion increases as rc decreases. A downwelling‐favorable wind component along the upstream coast (τsx) favors separation by increasing total plume speed. An upwelling‐favorable wind component along the downstream coast (τsy) also increases offshore excursion. Winds blowing obliquely offshore with both these wind components advect the plume farther offshore. Wind‐driven currents that steer plumes in this situation include a downshelf jet originating on the upstream shelf and continuing around the coastal corner and beyond, offshore and upshelf surface transport downstream of the corner, and surface Ekman transport on the outer shelf. Multiple linear regressions quantify plume position sensitivity to rc, τsx, and τsy; results are discussed in a dynamical context. Globally, many river plumes interact with coastal corners under various wind conditions.

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Section: Discussionmentioning

confidence: 99%

Wind‐Enhanced Separation of Large‐Scale River Plumes From Coastal Corners

Whitney

2024

JGR Oceans

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“…Other wave effects, such as Stokes drift, wave setup, wave-driven nearshore currents, breaker-enhanced turbulent mixing, and wave-induced bottom streaming (e.g., Uchiyama et al, 2009;Uchiyama et al, 2010;Weir et al, 2011;Marchesiello et al, 2015;Uchiyama et al, 2017a;Akan et al, 2020;Wang et al, 2020;Wang et al, 2021), are also anticipated to significantly influence Lagrangian transport in coastal areas. The linear addition of Stokes drift to the Lagrangian equation of motion of the particle tracking models has been reported to improve reproducibility in the open ocean to a certain extent (e.g., Iwasaki et al, 2017;Matsushita et al, 2022). Nearshore currents, in particular transient rip currents (e.g., Fujimura et al, 2017;Uchiyama et al, 2017a;Fujimura et al, 2018), which occur intermittently and promote cross-shore exchange and dispersal extensively, must be considered to represent inter-reef larval transport.…”

Section: Discussionmentioning

confidence: 99%

“…The 3-D Lagrangian transport of coral larvae was then numerically simulated using the precomputed 3-D flow field of the ROMS-L4 model output provided at 2 h intervals. An offline 3-D Lagrangian particle tracking model for ROMS was exploited (Carr et al, 2008), which has frequently been used in numerical studies on Lagrangian dispersal of virtual fluid parcels (e.g., Romero et al, 2013;Romero et al, 2016;Masunaga et al, 2022), larvae and eggs of marine fauna (Mitarai et al, 2009;Uchiyama et al, 2018b;Uchiyama et al, 2018c;Takeda et al, 2021), and even microplastic particles (Matsushita et al, 2022) with ample validations against in situ datasets of Lagrangian floats and drifters. Corals have various biological characteristics, such as larval behavior, larval precompetency period, and larval reproduction duration, depending on their species, habitat, and other conditions (Shlesinger and Loya, 1985;Baird et al, 2009).…”

Section: Offline Lagrangian Particle Tracking Model For Romsmentioning

confidence: 99%

Quantifying connectivity between mesophotic and shallow coral larvae in Okinawa Island, Japan: a quadruple nested high-resolution modeling study

2023

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Coral bleaching has recently been occurring extensively across the world’s oceans, primarily because of high water temperatures. Mesophotic corals that inhabit depths of approximately 30–150 m are expected to survive bleaching events and reseed shallow water corals afterward. In Okinawa, Japan, mesophotic coral ecosystems have been reported to serve as a refuge for preserving the genotypic diversity of bleaching-sensitive corals. The connectivity of larval populations among different habitats is a key element that determines the area to be conserved in desirable coral ecosystems. Because coral larvae are largely transported passively by ambient oceanic currents, particularly in the horizontal direction, numerical ocean circulation models greatly help to quantify connectivity with detailed spatiotemporal network structures. The present study aimed to quantify the short-distance connectivity of shallow and mesophotic coral larvae in reef areas on the northwest coast of Okinawa Island. To this end, a quadruple nested high-resolution synoptic ocean model at a lateral spatial grid resolution of 50 m was developed, which was capable of realizing detailed coastal currents influenced by complex nearshore topography, and coupled with an offline 3-D Lagrangian particle-tracking model. After validating the developed model, short-distance horizontal coral connectivity across reef areas on the northwest coast was successfully evaluated. The alongshore lateral connectivity had apparent asymmetry caused by depth-dependent horizontal currents, whereas the larvae spawned at shallow and mesophotic depths were reachable to each other. Such across-depth larval dispersal was attributable to the mixed-layer depth in the spawning period, viz., the boreal spring, which approximately coincides with the boundary between shallow and mesophotic coral, leading to the intensive vertical exchange of virtual larvae.

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“…The initial and side boundary conditions for the ROMS were provided by monthly climatology of the assimilative JCOPE2 oceanic reanalysis (Miyazawa et al, 2009). A one-way offline nesting technique was employed to convey the parent JCOPE2 to the child ROMS model with grid resolution refinement (e.g., Mason et al, 2010;Uchiyama et al, 2014;Kamidaira et al, 2017;Uchiyama et al, 2017;Kamidaira et al, 2018;Uchiyama et al, 2018a;Uchiyama et al, 2018b;Uchiyama et al, 2018c;Tada et al, 2018;Masunaga et al, 2018;Kamidaira et al, 2019;Masunaga et al, 2019;Zhang et al, 2019;Kurosawa et al, 2020;Kamidaira et al, 2021;Takeda et al, 2021;Uchiyama et al, 2022;Masunaga et al, 2022;Matsushita et al, 2022). Therefore, the horizontal grid spacing was successfully reduced from 1/12°(~10 km) of the JCOPE2 reanalysis to 3 km of the ROMS model, and vertically into stretched 32 s-layers (Shchepetkin and McWilliams, 2005) with grid height refinement near the surface and bottom to adequately resolve the boundary layers.…”

Section: Ocean Circulation Modelmentioning

confidence: 99%

Seasonal variability of upper ocean primary production along the Kuroshio off Japan: Roles of eddy-driven nutrient transport

et al. 2022

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We assessed spatial and seasonal variabilities of eddy-driven vertical nutrient fluxes, which are essential for maintaining primary production in the upper ocean. A climatological model based on a Regional Oceanic Modeling System (Regional Oceanic Modeling System) coupled with a Nutrient Phytoplankton Zooplankton and Detritus (NPZD) biogeochemical model at a submesoscale eddy-permitting resolution was used to investigate the mechanisms driving such variabilities around the Kuroshio, off the coast of Japan. The model realistically reproduced the spatial segmentations in primary production on both sides of the Kuroshio path with a higher chlorophyll-a concentration on the northern side than the southern side. In winter, downward eddy-induced nitrate flux is predominantly provoked in the upstream Kuroshio region (KR), while upward nitrate fluxes prevail in the downstream Kuroshio Extension (KE) region, due to both shear and baroclinic instabilities. Baroclinic instability plays a crucial role in inducing seasonal variability, leading to enhancement (reduction) of the eddy flux in winter (summer), particularly in regions away from the Kuroshio axis. Furthermore, we found that the influence of the Izu-Ogasawara Ridge, located in the KR, on regional dynamics and resultant spatial variability of the biogeochemical response are mostly confined in the KR. The Kuroshio is less turbulent in the upstream of the ridge, while it becomes unstable to shed mesoscale eddies in laterally wider and vertically deeper regions downstream. Consequently, although the near-surface nitrate concentration is lower downstream, the upward eddy-driven nitrate flux is more effective in maintaining active primary production due to the shear and baroclinic instabilities in winter.

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Fate of river-derived microplastics from the South China Sea: Sources to surrounding seas, shores, and abysses

Cited by 9 publications

References 69 publications

Wind‐Enhanced Separation of Large‐Scale River Plumes From Coastal Corners

Wind‐Enhanced Separation of Large‐Scale River Plumes From Coastal Corners

Quantifying connectivity between mesophotic and shallow coral larvae in Okinawa Island, Japan: a quadruple nested high-resolution modeling study

Seasonal variability of upper ocean primary production along the Kuroshio off Japan: Roles of eddy-driven nutrient transport

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