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A large fraction of the organic carbon derived from land that is transported through inland waters is decomposed along river systems and emitted to the atmosphere as carbon dioxide (CO 2 ). The Amazon River outgasses nearly as much CO 2 as the rainforest sequesters on an annual basis, representing ∼25% of global CO 2 emissions from inland waters. However, current estimates of CO 2 outgassing from the Amazon basin are based on a conservative upscaling of measurements made in the central Amazon, meaning both basin and global scale budgets are likely underestimated. The lower Amazon River, from Óbidos to the river mouth, represents ∼13% of the total drainage basin area, and is not included in current basin-scale estimates. Here, we assessed the concentration and evasion rate of CO 2 along the lower Amazon River corridor and its major tributaries, the Tapajós and Xingu Rivers. Evasive CO 2 fluxes were directly measured using floating chambers and gas transfer coefficients (k 600 ) were calculated for different hydrological seasons. Temporal variations in pCO 2 and CO 2 emissions were similar to previous observations throughout the Amazon (e.g., peak concentrations at high water) and CO 2 outgassing was lower in the clearwater tributaries compared to the mainstem. However, k 600 -values were higher than previously reported upstream likely due to the generally windier conditions, turbulence caused by tidal forces, and an amplification of these factors in the wider channels with a longer fetch. We estimate that the lower Amazon River mainstem emits 0.2 Pg C year −1 within our study boundaries, or as much as 0.48 Pg C year −1 if the entire spatial extent to the geographical mouth is considered. Including these values with updated basin scale estimates and estimates of CO 2 outgassing from small streams we estimate that the Amazon running waters outgasses as much as 1.39 Pg C year −1 , increasing the global emissions from inland waters by 43% for a total of 2.9 Pg C year −1 . These results highlight a large missing gap in basin-scale carbon budgets along the complete continuum of the Amazon River, and likely most other large river systems, that could drastically alter global scale carbon budgets.

Here we present direct measurements of the biological breakdown of 13C‐labeled substrates to CO2 at seven locations along the lower Amazon River, from Óbidos to the mouth. Dark incubation experiments were performed at high and low water periods using vanillin, a lignin phenol derived from vascular plants, and at the high water period using four different 13C‐labeled plant litter leachates. Leachates derived from oak wood were degraded most slowly with vanillin monomers, macrophyte leaves, macrophyte stems, and whole grass leachates being converted to CO2 1.2, 1.3, 1.7, and 2.3 times faster, respectively, at the upstream boundary, Óbidos. Relative to Óbidos, the sum degradation rate of all four leachates was 3.3 and 2.6 times faster in the algae‐rich Tapajós and Xingu Rivers, respectively. Likewise, the leachates were broken down 3.2 times more quickly at Óbidos when algal biomass from the Tapajós River was simultaneously added. Leachate reactivity similarly increased from Óbidos to the mouth with leachates breaking down 1.7 times more quickly at Almeirim (midway to the mouth) and 2.8 times more quickly across the river mouth. There was no discernible correlation between in situ nutrient levels and remineralization rates, suggesting that priming effects were an important factor controlling reactivity along the continuum. Further, continuous measurements of CO2, O2, and conductivity along the confluence of the Tapajós and Amazon Rivers and the Xingu and Jarauçu Rivers revealed in situ evidence for enhanced O2 drawdown and CO2 production along the mixing zone of these confluences.

The purpose of this study was to use the informations relating to parasite crustaceans species that was published over the course of one century (1913 to 2013), in order to search for infestation and distribution patterns among these ectoparasites in Brazilian freshwater fish species. This search was carried out on 445 samples of 119 host fish of 27 families within the orders Characiformes, Perciformes, Clupeiformes, Mugiliformes, Osteoglossiformes, Symbranchiformes, Tetraodontiformes and Siluriformes from various regions of Brazil. We organized different host-parasite systems into matrices grouping species at different taxonomic and infestation levels and according to host parameters. Five families of parasites (Ergasilidae, Argulidae, Lernaeidae, Lernaeopodidae and Cymothoidae) distributed into 76 species of 27 genera were analyzed in the host samples, which presented dominance of Ergasilidae species, mainly from the genus Ergasilus. Some crustaceans are host and site-specific, especially in relation to fish in particular habitats and lifestyles (e.g. Perulernaea gamitanae, Anphira branchialis and Riggia paranensis), while other parasites frequently have no preference (e.g. Lernaea cyprinacea and Braga patagonica). We found broadly similar distribution patterns for some crustacean species among the different localities, whereas other species showed well-defined geographical patterns, and these findings were discussed.Keywords: Amazon, Branchiura, Copepoda, host, Isopoda, parasite. ResumoO objetivo deste estudo foi utilizar as informações relacionadas com espécies de crustáceos parasitas, que foram publicados durante um século (1913 a 2013), para procurar padrões de infestação e distribuição desses ectoparasitos em espécies de peixes de água doce do Brasil. Esta pesquisa foi realizada em 445 amostras de 119 peixes hospedeiros de 27 famílias de Characiformes, Perciformes, Clupeiformes, Mugiliformes, Osteoglossiiformes, Symbranchiformes, Tetraodontiformes e Siluriformes das diversas regiões do Brasil. Foram organizados em matrizes de agrupamento diferentes sistemas parasito-hospedeiros em diferentes níveis taxonômicos, níveis de infestação e parâmetros dos hospedeiros. Cinco famílias (Ergasilidae, Argulidae, Lernaeidae, Lernaeopodidae e Cymothoidae) de parasitos, distribuídos em 76 espécies de 27 gêneros, foram analisados em amostras dos hospedeiros, que apresentaram dominância de espécies Ergasilidae principalmente do gênero Ergasilus. Alguns crustáceos são hospedeiros e sítios-específicos no hospedeiro, especialmente peixes de determinados hábitat e estilo de vida (por exemplo, Perulernaea gamitanae, Anphira branchialis e Riggia paranensis), enquanto outros parasitos não têm qualquer preferência (por exemplo, Lernaea cyprinacea e Braga patagonica). Foram encontrados padrões muito semelhantes na distribuição de algumas espécies de crustáceos entre as diferentes localidades, enquanto outras espécies mostraram um padrão geográfico bem definido, o que foi discutido aqui.