Publication Date:
2024-02-07
Description:
As the world's largest marginal sea, biogeochemical cycling of nitrite (NO2-) in the South China Sea (SCS) is still unclear. NO2- concentration generally shows a peak at or near the base of the sunlit euphotic zone, which is called primary NO2- maximum (PNM). The PNM appears widely in the SCS, but its formation mechanism has not yet been realized. In this study, the dual isotopes of NO2- are used for the first time to explore the NO2- cycle and PNM formation in the northern SCS (NSCS). We propose that the formation of the PNM in the NSCS is mainly driven by ammonia (NH3) oxidation. A steady-state model is used to estimate the biogeochemical cycling rates of NO2- in the NSCS. Our results show that both the oxidation rate of NH3 and the assimilation rate of NO2- are significantly reduced from the shelf to the basin. Notably, the role of NO2- oxidation in the basin is not negligible, although the assimilation of NO2- mainly represents the fate of NO2- in the NSCS. The residence time of NO2- implies that the cycle of NO2- is dynamic and the PNM is an active signal in the NSCS. Our results further demonstrate the importance of NH3 oxidation in the formation of PNM in the marginal sea, which can be applied in global marginal seas to gain a deeper understanding of marine nitrogen (N) cycle.
Type:
Article
,
PeerReviewed
Format:
text
Format:
text
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