The Amazon River plays a far more significant role in drawing carbon dioxide from the atmosphere than previously understood, according to a new study by a team of international scientists. Nutrients from the river's outflow travel thousands of miles past the continental shelf, influencing the carbon cycling in the tropical ocean.
A large sediment plume from the mouth of the Amazon River expands outward into the tropical Atlantic Ocean. NASA
"We were surprised to find that a surface plume of fresh Amazon water about the size of Texas had traveled so far out to sea,"said Ed Carpenter, professor of biology and Romberg Tiburon Center researcher, a co-author of the study. "Our research showed that nutrients and phosphorus from the Amazon outflow stimulate the production of nitrogen-fixing ocean organisms that convert gaseous nitrogen to amino acids and protein." This food boosts the production and number of the ocean organisms that absorb greenhouse gasses from the atmosphere and turn them into organic solids that sink to the bottom of the sea and die.
The Amazon River has the largest discharge of any of the world's rivers by volume and is the largest drainage basin on the planet. It accounts for 18 percent of all river output into the world's oceans. Previously scientists had only studied the movement of river outflow closer to shore.
"We are really excited about this discovery and are eager to learn if outflow from the Congo, the world's second largest river, has the same effect on ocean productivity," Carpenter said.