What is it about?
Based on field observations and modeling, we estimated the influence of coupled biological–physical oceanographic processes on potential POM dynamics, fluxes, and horizontal transport in the SYS. The Subei coast region had considerably higher POM than that found in other subregions of the SYS. The C/N ratio in the Subei coast region deviated more or less from the Redfield ratio during winter and spring, indicating the potential impact of robust physical forcing. The effect of biological processes was notable in the central basin with the C/N ratio broadly matching the Redfield ratio, which can also be proven by the vertical distribution of POC%.
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Why is it important?
Using total suspended matter (TSM), particulate organic carbon (POC), and particulate nitrogen data, this study investigated the potential vertical POC flux and transport in the South Yellow Sea (SYS). The biogenic production and resuspension fraction (i.e., the proportion of resuspended particles in TSM) were estimated using an ecosystem model and a vertical mixing model. They were verified against reported sediment trap and primary productivity data. The estimates of resuspension fraction showed substantial uncertainty of 50% in summer likely owing to the potential errors of model parameter estimation and the influence of other unexplored biophysical processes such as biological degradation, upwelling, and monsoons; however, the estimates of resuspension fraction showed less uncertainty in other seasons (<20%). Few previous studies have considered the specific influence of resuspension on the dynamics and budget of particulate organic matter (POM) in the SYS. This study proposed a reasonably simple and effective method to address this issue, which was applied to systematic examination of the variation of vertical POM flux with the change of coupled biological–physical oceanographic processes along the Subei coast and in the SYS central basin. The influence of horizontal transport from the Subei coast to the central basin may cause an overestimation of >10% of the resuspension fraction. It will be necessary to acquire additional field data covering a larger spatiotemporal scale to establish an integrated network of the SYS carbon budget.
Perspectives
The present study addressed this important issue using total suspended matter (TSM), POC, and particulate nitrogen (PN) data and examined the potential vertical POC flux and subsequent transport in the SYS using different models. We combined an ecosystem model and a vertical mixing model to investigate how biogenic processes, resuspension, and potential horizontal cross-shelf transport (i.e., from coastal areas to the central region) might contribute to the carbon budget between the Subei coast and central SYS basin. The ecosystem model was used to estimate the carbon/nitrogen dynamics of phytoplankton, heterotrophs, and detritus, although we had no means of judging the accuracy of the model results because it is difficult for us to precisely divide TSM into contributions of phytoplankton, heterotrophs, and detritus. However, the findings of this study support a comprehensive understanding of how POM dynamics and stoichiometries reflect a coupled response to biological and physical forcings both seasonally and spatially (from the Subei coast to the central SYS basin) in a marginal sea.
Dr Wei-Dong Zhai
Shandong University
Read the Original
This page is a summary of: Biological–physical oceanographic coupling influencing particulate organic matter in the South Yellow Sea, Frontiers in Marine Science, August 2022, Frontiers,
DOI: 10.3389/fmars.2022.919423.
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