The Nitrogen Cycle in Oxic and Anoxic Water (image) University of Rochester Share Print E-Mail Caption In the nitrogen cycle, phytoplankton and other marine plants turn nitrate (NO3) into organic nitrogen during photosynthesis. The organic nitrogen sinks into the deep ocean, where microbes "eat" the organic nitrogen and use oxygen to respire and turn the nitrogen into nitrate. Ocean currents cycle the nitrate back to the surface ocean and nitrogen is neither lost nor gained (left panel). When oxygen runs out however, some organisms respire using nitrate instead of oxygen, converting the nitrate back into nitrogen gas, driving it into the atmosphere and removing it from the oceans. Credit University of Rochester illustration / Michael Osadciw Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.