Document Type

Article

Publication Date

2020

DOI

10.3389/feart.2020.537332

Publication Title

Frontiers in Earth Science

Volume

8

Pages

537332 (17 pp)

Abstract

We have investigated the effect of eddies (cold and warm eddies, CEs and WEs) on the nutrient supply to the euphotic zone and the organic carbon export from the euphotic zone to deeper parts of the water column in the northern South China Sea. Besides basic hydrographic and biogeochemical parameters, the flux of particulate organic carbon (POC), a critical index of the strength of the oceanic biological pump, was also measured at several locations within two CEs and one WE using floating sediment traps deployed below the euphotic zone. The POC flux associated with the CEs (85 ± 55 mg-C m −2 d −1) was significantly higher than that associated with the WE (20 ± 7 mg-C m −2 d −1). This was related to differences in the density structure of the water column between the two types of eddies. Within the core of the WE, downwelling created intense stratification which hindered the upward mixing of nutrients and favored the growth of small phytoplankton species. Near the periphery of the WE, nutrient replenishment from below did take place, but only to a limited extent. By far the strongest upwelling was associated with the CEs, bringing nutrients into the lower portion (∼50 m) of the euphotic zone and fueling the growth of larger-cell phytoplankton such as centric diatoms (e.g., Chaetoceros, Coscinodiscus) and dinoflagellates (e.g., Ceratium). A significant finding that emerged from all the results was the positive relationship between the phytoplankton carbon content in the subsurface layer (where the chlorophyll a maximum occurs) and the POC flux to the deep sea.

Comments

© 2020 Shih, Hung, Tuo, Shao, Chow, Muller, and Cai. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original authors and the copyright owners are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.

Original Publication Citation

Shih, Y.-Y., Hung, C.-C., Tuo, S.-H., Shao, H.-J., Chow, C. H., Muller, F., & Cai, Y.-H. (2020). The impact of eddies on nutrient supply, diatom biomass and carbon export in the Northern South China Sea. Frontiers in Earth Science, 8, 17 pp., Article 537332. https://doi.org/10.3389/feart.2020.537332

ORCID

0000-0003-0620-2001 (Tuo)

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