Consider the Following Representation of the Marine Nitrogen Cycle: ‬

question 109

Multiple Choice

Consider the following representation of the marine nitrogen cycle: ‬ NH₄⁺ (ammonium ion) plays an important role in the nitrogen cycle, and is excreted by many aquatic organisms. Why is the fixation of atmospheric nitrogen necessary if there is a readily available source of biologically usable nitrogen already present in aquatic biomes?

• A)Atmospheric nitrogen serves as a reservoir to be converted when other forms of nitrogen have been depleted from an area.
• B)Ammonium ions will eventually be oxidized to nitrogen gas (N₂)that will be returned to the atmosphere.
• C)Nitrogen still must be fixed from the atmosphere so that global climate doesn't change.
• D)Nitrogen must be fixed so that terrestrial plants can utilize it for growth.

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