Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Discussion papers
https://doi.org/10.5194/bg-2019-88
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-88
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 25 Mar 2019

Research article | 25 Mar 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Spring net community production and its coupling with the CO2 dynamics in the surface water of the northern Gulf of Mexico

Zong-Pei Jiang1,2, Wei-Jun Cai2, John Lehrter3, Baoshan Chen2, Zhangxian Ouyang2, Chengfeng Le1, and Brian J. Roberts4 Zong-Pei Jiang et al.
  • 1Ocean College, Zhejiang University, Zhoushan, Zhejiang, China
  • 2School of Marine Science and Policy, University of Delaware, Newark, Delaware, USA
  • 3University of South Alabama, Alabama, USA
  • 4Louisiana Universities Marine Consortium, Louisiana, USA

Abstract. Net community production (NCP) in the surface mixed layer of the northern Gulf of Mexico (nGOM) and its coupling with the CO2 system were examined during the productive spring season. NCP was estimated using multiple approaches: (1) underway O2 and Ar ratio, (2) light/dark bottle oxygen incubations, and (3) non-conservative changes in dissolved inorganic carbon and nutrients; in order to assess uncertainties and compare the temporal-spatial scales associated with the different approaches. NCP estimates derived from various methods showed similar pattern along the river-ocean mixing gradient. The NCPO2Ar estimated from the high resolution O2 and Ar underway measurement is characterized by negative rates (−25.4 mmol C m−2 d−1) at the high nutrient and high turbidity river end (salinity < 5) resulting from light limitation and the influence of terrestrial carbon input. NCPO2Ar had highest rates (up to 235 mmol C m−2 d−1) in the river plume regions at intermediate salinities between 15 to 30 where light and nutrient were both favorable for phytoplankton production. NCPO2Ar rates were much lower (1.2 mmol C m−2 d−1) in high salinity (salinity > 31) oligotrophic offshore waters due to nutrient limitation. Air-sea CO2 fluxes generally showed corresponding changes from being a strong CO2 source in the river channel to a CO2 sink in the plume. CO2 fluxes were near zero in offshore waters indicating balanced autotrophy and heterotrophy at these sites. Overall, the surface water in the nGOM (93–89.25° W, 28.5–29.5° N) was strongly autotrophic during the spring season in spring 2017 with mean NCP rate of 21.2 mmol C m−2 d−1 and as a CO2 sink of −6.7 mmol C m−2 d−1. By using a 1-D model, we demonstrated that a temporal mismatch between in situ biological production and gas exchange of O2 and CO2 could result in decoupling between NCP and CO2 flux (e.g., autotropic water as a CO2 source outside the Mississippi river mouth and heterotopic water as a CO2 sink near the Atchafalaya Delta). This decoupling was a result of in situ biological production superimposed on the lingering background pCO2 from the source water because of the slow air-sea CO2 exchange rate and buffering effect of the carbonate system.

Zong-Pei Jiang et al.
Interactive discussion
Status: open (until 13 May 2019)
Status: open (until 13 May 2019)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Zong-Pei Jiang et al.
Zong-Pei Jiang et al.
Viewed  
Total article views: 208 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
172 35 1 208 5 0 0
  • HTML: 172
  • PDF: 35
  • XML: 1
  • Total: 208
  • Supplement: 5
  • BibTeX: 0
  • EndNote: 0
Views and downloads (calculated since 25 Mar 2019)
Cumulative views and downloads (calculated since 25 Mar 2019)
Viewed (geographical distribution)  
Total article views: 142 (including HTML, PDF, and XML) Thereof 141 with geography defined and 1 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited  
Saved  
No saved metrics found.
Discussed  
No discussed metrics found.
Latest update: 18 Apr 2019
Publications Copernicus
Download
Short summary
The biological production and air-sea CO2 exchange in the surface water in the northern Gulf of Mexico during springtime was mainly controlled by the changes in the availability of light and nutrients during the river-ocean mixing process. The slow air-sea CO2 exchange rate and buffering effect of the CO2 system may result in decoupling between biological production and CO2 flux.
The biological production and air-sea CO2 exchange in the surface water in the northern Gulf of...
Citation