Anemic Phytoplankton Absorb Less Carbon than Thought

Phytoplankton in the Pacific Ocean are starved for iron, and as a result these microscopic plants soak up less of the greenhouse gas carbon dioxide than was previously thought, researchers have found. Although the difference in carbon uptake is not enough to perturb climate predictions significantly, the research should lead to an improved understanding of how climate changes will affect phytoplankton's ability to take up carbon.

The world's oceans tend to absorb carbon dioxide in the form of carbonate, but the Pacific Ocean actually emits CO2 in areas of cold, upwelling water that warms as it reaches the surface, releasing the gas. Phytoplankton thrive on this CO2, using it to drive their photosynthesis. But the plankton don't grow very fast given the amount of nitrogen and phosphorus at their disposal. To find out why, marine researchers took a zigzagging 12-year journey through the Pacific, collecting tens of thousands of plankton samples. Fluorescence imaging gave them a measure of the plankton's photosynthesis.