Describe two recently recognized sources of organic nitrogen in the open ocean
Air is composed of almost 80% nitrogen. They are usually present as inert nitrogen gas. Several bacteria fix nitrogen to form organic nitrogen-containing compounds that are usable by giving organisms through the nitrogen cycle.
In the nitrogen cycle, the inert nitrogen gas is fixed by several bacteria and lightning activity to form ammonia by nitrogen fixation. Ammonia is toxic to most living organisms. Ammonia gets converted to nitrites and nitrates by nitrification by the action of nitrifying bacteria. Living organisms use nitrates, nitrite, and ammonia to synthesize amino acids and proteins. When the living organisms die, they release them into the environment completing the nitrogen cycle.
The major sources of organic nitrogen in the marine ecosystem are-
- Amino acids, either in the free form or as part of oligopeptides.
- Urea production and catabolism through the urea cycle by marine organisms.
- Ammonia production by marine fishes.
- Nitrogen-containing fertilizers that leech to the groundwater and ultimately end up in the open ocean.
- Marine organisms such as diatoms dwell on the nutrient-rich deep ocean water at the bottom of the open ocean and bring back nitrates.
- Several bacterioplanktons act upon dead and decaying marine life forms to bring back ammonia and nitrates. The nitrates and ammonia brought by bacterioplanktons are used by phytoplankton to generate organic nitrogen.
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