Award: OCE-1133277

The emphasis of this multi-disciplinary, multi-institutional project was to understand the role of river discharge from the Amazon River on phytoplankton and zooplankton communities of the Amazon plume. The Amazon River is the largest river system in the world. Since it flows through the worldÆs largest and most densely forested basins, it carries with it tremendous amounts of sediments, nutrients as well as particulate and dissolved organic matter that can have a profound impact on phytoplankton and zooplankton communities of the Western North Atlantic (WTNA) Ocean. Phytoplankton blooms triggered by the Amazon River plume are believed to be responsible for significant carbon dioxide drawdown from the atmosphere. Field work included three research cruises to the Amazon River Plume during different periods of river discharge. The data obtained allowed us to address the following questions: 1) Is the discharge of freshwater from the Amazon River a significant driver of change in the environment of the WTNA Ocean? 2) Are changes in the hydrological, chemical and optical changes brought about by the interaction of freshwater from the river with oceanic waters significant enough to cause large community changes across the plume? 3) What are the major environmental variables responsible for changes in phytoplankton community structure across the plume? Phytoplankton species composition data from 2010, 2011 and 2012 showed shifts in the distribution of phytoplankton groups across depending on the discharge from the Amazon River plume and the size and position of the plume. When examined in the context of the physical and chemical gradients of the plume these datasets in particular from 2010, allowed us to posit that the succession in phytoplankton communities across the salinity and nutrient gradient may in fact be regulated by dissolved inorganic carbon (DIC) concentrations, carbon concentrating mechanisms (CCMs), and to a lesser degree by dissolved inorganic nitrogen or phosphorous availability. Carbon dioxide sensitivity experiments undertaken using natural phytoplankton assemblages as well as laboratory cultures of phytoplankton drawn from the Amazon River Plume provided us with strong indications that phytoplankton communities across the river plume is partly regulated by DIC. Our component of the project provided hands-on research opportunities for three undergraduate students from the USA and interaction with two graduate students from Brazil. Of the three students from the USA, two are currently pursuing higher degrees in the USA and one in Sweden. In addition, two summer interns, Ms Therese Chen, undergraduate from Barnard College, New York and Ms. Tegan Galina, junior High School Student, from Bronx Science School who undertook CO2 perturbation experiments at Lamont Doherty Earth Observatory are submitting applications for higher studies. Other community outreach activities were undertaken through the project website http://amazoncontinuum.org Data collected over the course of this study has been submitted to National Science Foundation sponsored Data Archives at BCO-DMO (http://www.bco-dmo.org/). Last Modified: 12/30/2014 Submitted by: Joaquim I Goes