Project Leader:
Dr. Ajit Subramaniam
Earth Institute Contact: Dr. Ajit Subramaniam
Locations: Atlantic Ocean
Description:
This project aims to assess the impact of seasonal nutrient outflow from tropical rivers on the marine environment. Specifically, the Tropical North Atlantic Ocean exhibits high primary productivity (PP) relative to other tropical open ocean environments with substantial contributions from two cyanobacterial nitrogen-fixers (diazotrophs) - freeliving Trichodesmium and the diatom endosymbiont Richelia. The two diazotrophs have very different spatial and temporal distributions in the Tropical North Atlantic, due largely to changes in dissolved iron, phosphorus, and silicate introduced by rivers. Diazotroph-Diatom Associations (DDA) dominate moderate salinity waters away from the continental shelf while Trichodesmium is the dominant large diazotroph elsewhere. Carbon (C) and nitrogen (N) fixed by these two diazotrophs have different fates – Trichodesmium releases fixed C and N near the surface that is then available to heterotrophic bacteria and other phytoplankton, while DDA sink intact out of surface waters, contributing to higher dissolved inorganic C drawdown. Sedimentation of DDA in the Amazon River plume, a hitherto unrecognised process, may contribute to the sequestration of up to 15 TgCy-1.
EI Unit:
Lamont-Doherty Earth Observatory (LDEO)
Cross Cutting Themes:
Climate and Society
Core Disciplines:
Earth Sciences
Project Web Site:
http://www.ldeo.columbia.edu/~ajit/tropicalrivers/tropicalrivers.html
Funding Agency:
NASA
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