Net Ecosystem Exchange of the Lower Amazon River - from Land to the Ocean and Atmosphere

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River systems are becoming progressively recognized as significant components of the global carbon cycle because they modulate and adjust the carbon dynamics not only of their watersheds but also of their marine receiving waters. Their primary role is as an immense source of outgassing of CO2 from inland waters to the atmosphere. If this effect is important, then the global terrestrial CO2 sink may prove to be smaller than current estimations indicate. Unraveling the processes that occur as water travels downstream and into the ocean is critical to understanding the role of freshwater ecosystems in global C cycling, yet a mechanistic understanding of these fluxes remains elusive. Recent advances in technology allow exciting new work that has not been previously possible. Riverine systems can now be effectively examined and understood through the lenses of Net Ecosystem Exchange. The overall objective of this project is to examine the processes that govern the movement and transitions of carbon through the lower reach of the Amazon River, from Óbidos (the last traditional measuring station on the Amazon), to the ocean. An ambitious field and laboratory study, combining cutting edge geochemical and geospatial analyses, will explore the influence of downstream processing on globally-relevant geochemical fluxes.The research itself will promote significantly greater understanding of the broader role of tropical rivers in the global carbon cycle, with the potential to shift the paradigm of how the transport and reaction of organic matter by rivers is viewed. A unique and extensive partnership with the Brazilian science community, via support from the funding agency FAPESP, will promote not only the science but significant capacity building, of both US and Brazilian students. The project team will address societal challenges in the region; as agriculture, fossil fuel exploration and hydropower demands progressively stress the lower Amazon.