Sediment Resuspension as a Major Contributor to Sinking Particles in the Northwestern South China Sea: Evidence From Observations and Modeling

Abstract

The lateral advection of sinking particles is a well-known phenomenon in the South China Sea (SCS) and has a significant impact on the estimation of the efficiency of the biological carbon pump. However, little is known about the sources and pathways of sinking particles. Here, we present benthic and freshwater diatom fluxes and relative abundances collected by a sediment trap deployed at a water depth of 1,000 m and more than 500 m above the seafloor in the northwestern SCS, indicating that laterally transported resuspended sediment accounts for a significant part of the particle flux to the deep sea. A Lagrangian particle tracking model (LPTM) revealed that the resuspended particles likely originated from the neighboring continental slope, approximately 12–145 km to the west of the study site. Sediment trap observations and the LPTM together indicated that the impact of resuspended sediment occurred mainly in the deep water, and especially strong sediment resuspension was related to summer monsoon-induced coastal upwelling. The results suggest that particle resuspension has an important impact on the biological pump as well as on paleoenvironmental reconstructions of the SCS.

Biological carbon pump responses to multiscale physical processes: a review of sediment trap studies in the South China Sea

“…These extinct coccoliths probably sourced from the Miocene and remaining in the sediment cover to the west and south of the Dongsha Islands, which somehow lateral transported to the northern basin (Priyadarshani et al, 2019). Again groups of benthic and freshwater diatoms were also found in the trap samples from the northwestern SCS, with the abundances of 1.5-6.9% (Ran et al, 2022). However, the lateral contribution is currently hard to quantify due to the lack of information as to the abundance of benthic diatoms and reworked coccoliths in the surface sediment in the northern and northwestern SCS.…”

Seasonal variations of siliceous microplankton fluxes and radiolarian assemblages linked to environmental conditions in Prydz Bay polynya, Eastern Antarctica

“…Quantitative radiolarian and diatom slides were prepared according to the methods developed based on the previous studies (Wang et al, 2006;Zhang et al, 2009;Ren et al, 2021;Ran et al, 2022). Subsamples of each aliquot (1/32 to 3/32, depending on sample amount) were treated with HCl (~10%) and H 2 O 2 (~30%) to generate residues.…”

Reactive iron as an important reservoir of marine organic carbon over geological timescales

“…In our study,  13 CFeR-OC in both sediment cores are typical for marine-sourced OC and the high molar ratio of FeR-OC to FeR indicates coprecipitation as an important binding mechanism. We propose that a large proportion of FeR-OC is formed at the redox interface in marine environments, which could be formed either autochthonously after deposition, or allochthonouly in neighbouring surface sediments and transported to the core location as resuspended particulates 42,43 .…”