Estuaries worldwide are ecosystems under the highest pressure due to their heavy use by humans and their connectivity to strongly impacted drainage basins. Estuaries are also critical export control points that determine how much of allochthonous nutrients from rivers reach the open ocean where they fertilize additional Estuaries worldwide are ecosystems under the highest pressure due to their heavy use by humans and their connectivity to strongly impacted drainage basins. Estuaries are also critical export control points that determine how much of allochthonous nutrients from rivers reach the open ocean where they fertilize additional  Estuaries critically control the export of allochthonous nutrients to the ocean. The Amazon River contributes nearly one fifth of the global riverine freshwater input to the ocean and the drainage basins is impact by human activities. . The tremendous outflow of water and nutrients into the tropical Atlantic and Caribbean Sea has recently been linked to massive blooms of Sargassum in these areas. LLight and different nitrogen (N) species control the production of photo- and heterotrophs (in the following trophic functional groups: TFGs) in the different habitats along the river plume. However, the role of allochthonous N for the production in different pelagic habitats along the plume is still unclear. Discordant lines of evidence suggest that all or none of the allochthonous N reaches the open ocean. We therefore want to quantify the N processes and the involved TFGs that can lead to retention of allochthonous N or to its export beyond these areas.

First, a detailed examination of the effects of allochthonous N considering food webs and nutrient biogeochemistry will be achieved for the different habitats. Based on dedicated experiments during the project`s cruise (M174) the understanding for complex relationships will be studied including the regulation of the planktonic food web structure. The ultimate goal is to generate a data based characterization of the habitats along the plume to improve estimations of carbon sequestration and N export. This will be achieved by translating the empirical data into feasible modeling instructions for biogeochemical models developed in close cooperation with partners of the project

Estuaries worldwide are ecosystems under the highest pressure due to their heavy use by humans and their connectivity to strongly impacted drainage basins. Estuaries are also critical export control points that determine how much of allochthonous nutrients from rivers reach the open ocean where they fertilize additional

Estuaries worldwide are ecosystems under the highest pressure due to their heavy use by humans and their connectivity to strongly impacted drainage basins. Estuaries are also critical export control points that determine how much of allochthonous nutrients from rivers reach the open ocean where they fertilize additional Estuaries worldwide are ecosystems under the highest pressure due to their heavy use by humans and their connectivity to strongly impacted drainage basins. Estuaries are also critical export control points that determine how much of allochthonous nutrients from rivers reach the open ocean where they fertilize additional 

Estuaries worldwide are ecosystems under the highest pressure due to their heavy use by humans and their connectivity to strongly impacted drainage basins. Estuaries are also critical export control points that determine how much of allochthonous nutrients from rivers reach the open ocean where they fertilize additiona