@Article{Gagne-MaynardWKSCNBLDVKKR:2017:EvPrPr,
               author = "Gagne-Maynard, William C. and Ward, Nicholas D. and Keil, Richard 
                         G. and Sawakuchi, Henrique O. and Cunha, Alan C. da and Neu, Vania 
                         and Brito, Daimio C. and Less, Diani F. da Silva and Diniz, Joel 
                         E. M. and Val{\'e}rio, Aline de Matos and Kampel, Milton and 
                         Krusche, Alex V. and Richey, Jeffrey E.",
          affiliation = "{University of Washington} and {University of Washington} and 
                         {University of Washington} and {University of Washington} and 
                         {Universidade Federal do Amap{\'a} (UFAP)} and {Universidade 
                         Federal Rural da Amazonia (UFRAM)} and {Universidade Federal do 
                         Amap{\'a} (UFAP)} and {Universidade Federal do Amap{\'a} (UFAP)} 
                         and {Universidade Federal do Amap{\'a} (UFAP)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Universidade de S{\~a}o Paulo 
                         (USP)} and {University of Washington}",
                title = "Evaluation of primary production in the lower Amazon River based 
                         on a dissolved oxygen stable isotopic mass balance",
              journal = "Frontiers in Marine Science",
                 year = "2017",
               volume = "4",
                month = "Feb.",
             keywords = "Mass balance, Oxygen, Photosynthesis, Respiration, Tropical 
                         rivers.",
             abstract = "The Amazon River outgasses nearly an equivalent amount of CO2 as 
                         the rainforest sequesters on an annual basis due to microbial 
                         decomposition of terrigenous and aquatic organic matter. Most 
                         research performed in the Amazon has been focused on unraveling 
                         the mechanisms driving CO2 production since the recognition of a 
                         persistent state of CO2 supersaturation. However, although the 
                         river system is clearly net heterotrophic, the interplay between 
                         primary production and respiration is an essential aspect to 
                         understanding the overall metabolism of the ecosystem and 
                         potential transfer of energy up trophic levels. For example, an 
                         efficient ecosystem is capable of both decomposing high amounts of 
                         organic matter at lower trophic levels, driving CO2 emissions, and 
                         accumulating energy/biomass in higher trophic levels, stimulating 
                         fisheries production. Early studies found minimal evidence for 
                         primary production in the Amazon River mainstem and it has since 
                         been assumed that photosynthesis is strongly limited by low light 
                         penetration attributed to the high sediment load. Here, we test 
                         this assumption by measuring the stable isotopic composition of O2 
                         (\δ18O-O2) and O2 saturation levels in the lower Amazon 
                         River from {\'o}bidos to the river mouth and its major 
                         tributaries, the Xingu and Tapaj{\'o}s rivers, during high and 
                         low water periods. An oxygen mass balance model was developed to 
                         estimate the input of photosynthetic oxygen in the discrete reach 
                         from {\'o}bidos to Almeirim, midway to the river mouth. Based on 
                         the oxygen mass balance we estimate that primary production 
                         occurred at a rate of 0.39 ± 0.24 g O m3 d-1 at high water and 
                         1.02 ± 0.55 g O m3 d-1 at low water. This translates to 41 ± 24% 
                         of the rate of O2 drawdown via respiration during high water and 
                         67 ± 33% during low water. These primary production rates are 2-7 
                         times higher than past estimates for the Amazon River mainstem. It 
                         is possible that at high water much of this productivity signal is 
                         the result of legacy advection from floodplains, whereas limited 
                         floodplain connectivity during low water implies that most of this 
                         signal is the result of in situ primary production in the Amazon 
                         River mainstem.",
                  doi = "10.3389/fmars.2017.00026",
                  url = "http://dx.doi.org/10.3389/fmars.2017.00026",
                 issn = "2296-7745",
             language = "en",
           targetfile = "gagne_evaluation.pdf",
        urlaccessdate = "19 abr. 2024"
}