The Amazon River-Ocean Continuum

This special feature aims to make connections across both physical and disciplinary boundaries to improve our understanding of the Amazon River's contributions to the global carbon cycle. The Amazon River has the greatest discharge of any global river and accounts for ~18% of all of the riverine input to the oceans, more than the next seven largest rivers combined. Its impact on the western tropical North Atlantic includes nutrients, microorganisms, and fresh water fluxes that contribute to enhanced biological activity and carbon sequestration by a plume that can cover more than a million square kilometers of the tropical ocean. These contributions are sensitive to the quantity and composition of the river discharge itself, which is highly influenced by processes occurring in the river watershed, particularly the lower reach. This combined river-ocean continuum creates one of the world's largest environmental gradients on land and in the ocean, across 1000s of km from the Andes highlands and Amazonian forests, through the wetlands of the lower reach to the continental shelf, to the middle of the Atlantic Ocean. As such, the Amazon continuum serves as an ideal system for studying global change.

One of the key unifying conceptual frameworks in aquatic microbiology is the idea that the structure of planktonic communities both affects the biogeochemical cycling of nutrients and is structured by available nutrients. The combination of community structure and nutrient cycling in turn affects the export and sequestration of organic material (the biological carbon pump). Yet, predicting microbial community structure and activities, particularly in response to human forcing, has been elusive.

The feature aims to bring together river scientists and oceanographers to fill the gap between aquatic and marine ecosystems, and extend the tropical river continuum concept through the lower reach of the river to the open ocean. The main objective of this special feature is to improve our understanding of the processes and organisms responsible for carbon and nutrient cycling along the tropical river continuum, starting with the Amazon River, focusing on the lower reach, nearshore, and offshore tropical Atlantic, thus enhancing predictive capabilities under different global change scenarios. The submission of manuscripts examining microbial and biogeochemical processes driving the flow of carbon and nutrients along the continuum is particularly encouraged. Methodological approaches ranging from classical field measurements, to "omics," to modeling, are also encouraged.