Nitrogen-Fixing Phytoplankton (IMAGE)
Caption
Researchers from Princeton University and the Swiss Federal Institute of Technology in Zurich found that the wobble of the Earth on its axis controls the production of fertilizing nitrogen essential to the health of the ocean. The wobble, known as axial precession, causes an upwell of nitrogen-poor (but phosphorus-rich) water from the deep ocean roughly every 23,000 years. Blue-green algae such as Trichodesmium (above) feed on the phosphorous as they convert, or "fix," nitrogen in the air into a biologically active form that becomes part of the ocean's nitrogen cycle.
Credit
Image courtesy of the Center for Microbial Oceanography, University of Hawaii
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