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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2018-465
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-465
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 10 Dec 2018

Submitted as: research article | 10 Dec 2018

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). A final paper in BG is not foreseen.

The role of hydrodynamic and biogeochemistry on CO2 flux and pCO2 at the Amazon River mouth

Diani F. S. Less1,2, Alan C. Cunha2, Henrique O. Sawakuchi3,4, Vania Neu5, Aline M. Valério6, Nicholas D. Ward7,9, Daimio C. Brito8, Joel E. M. Diniz2, William Gagne-Maynard7, Carlos M. Abreu2,8, Milton Kampel6, Alex V. Krusche3, and Jeffrey E. Richey9 Diani F. S. Less et al.
  • 1Instituto de Ciências e Tecnologia das Águas, Universidade Federal do Oeste do Pará, Santarém, 68040-050, Brasil
  • 2Departamento de Meio Ambiente e Desenvolvimento, Universidade Federal do Amapá, Macapá, 68902-280, Brasil
  • 3Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, 13400-970, Brasil
  • 4Department of Ecology and Environmental Science, Umeå Universitet. KBC-huset, Linnaeus väg 6, 901 87 Umeå, Sweden
  • 5Instituto Sócio Ambiental e dos Recursos Hídricos, Universidade Federal Rural da Amazônia, Belém, 66077-530, Brasil
  • 6Divisão de Sensoriamento Remoto, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, 12227-010, Brasil
  • 7Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim, 98382, USA
  • 8Universidade do Estado do Amapá, Macapá, 68.900-070, Brasil
  • 9School of Oceanography, University of Washington, Seattle, 98195, USA

Abstract. Recent estimates indicate that the lower Amazon River outgasses significant amounts of carbon dioxide (CO2) that was not previously accounted for the global inland water carbon budget. Detailed evaluation of seasonal variability and controlling mechanisms behind the CO2 fluxes in this large and complex area remains incomplete. Previous observations throughout the Amazon basin showed that higher CO2 fluxes (FCO2) and partial pressure of CO2 (pCO2) occur during high water and higher wind intensity seasons. The influence of wind and water speed, depth of water column, as well as respiration of allochthonous and autochthonous organic matter, are frequently assigned as the main control variables. Here, we assess the influence of a set of biogeochemical and hydrodynamic parameters on the seasonal variation of FCO2 and pCO2 near the Amazon River mouth. FCO2, pCO2 and biogeochemical and hydrologic analyses were carried out from 2010 to 2016 during four different hydrological periods per year (N = 25) in the North Channel of the Amazon River mouth. FCO2 and pCO2 were used as independent variables and analyzed against 33 biogeochemical, hydrodynamic and meteorological parameters along the hydrological seasons. The highest FCO2 and pCO2 was obtained at high discharge season (11.28 ± 7.82 μmol m−2 s−1 and (4575 ± 429 μatm, respectively) when most of these parameters tend to be higher. Among the 33 parameters analyzed, the significant correlations with FCO2 and pCO2 (p < 0.05) observed were for water and air temperatures, dissolved oxygen, dissolved organic carbon, nitrate, dissolved inorganic nitrogen and pH. These variables could be considered suitable predictors for estimating pCO2 and FCO2 in the Amazon River mouth area. For a better estimation and understanding of carbon budgets in tropical rivers it is still required to verify and to quantify more deeply the relationship among CO2 evasion and others hydrodynamic, meteorological and biogeochemical variables.

Diani F. S. Less et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Diani F. S. Less et al.
Diani F. S. Less et al.
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Short summary
Biogeochemistry studies focused in carbon cycle in the Amazon River mouth are scarce. Our study provided a long-term quantification of CO2 fluxes and pCO2 and evaluation of the most important hydrodynamic, biogeochemical and meteorological parameters related to them. The highest FCO2 and pCO2 was obtained at high discharge season, water and air temperatures, dissolved oxygen, dissolved organic carbon, nitrate, dissolved inorganic nitrogen and pH could be considered predictors for pCO2 and FCO2.
Biogeochemistry studies focused in carbon cycle in the Amazon River mouth are scarce. Our study...
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