Status: this preprint has been withdrawn by the authors.
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. Richey9Diani F. S. Less et al.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
Received: 30 Oct 2018 – Discussion started: 10 Dec 2018
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.
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...