The nitrogen cycle is an important process in the ocean Consider the following statements abou...........

Geography World - Water Bodies

Download Solution PDF

The nitrogen cycle is an important process in the ocean. Consider the following statements about it.

1. Nitrogen enters the water through precipitation, runoff or from the atmosphere.

2. Nitrogen can be utilized by phytoplankton directly from the atmosphere.

3. Ammonia and urea are released into the water by vertical mixing of ocean layers.

Select the correct answer using the codes given below.

1 and 2 only

2 and 3 only

1 only

1 and 3 only

छोटे Courses बड़े Results

Master World - Water Bodies

Prepare through Micro-courses

Try Now

Explanation:

Statement 1: Without supplies of fixed nitrogen entering the marine cycle the fixed nitrogen would be used up in about 2000 years. While the overall cycle is similar to that of land, there are different players and modes of transfer for nitrogen in the ocean. Nitrogen enters the water through precipitation, runoff, or as N2 from the atmosphere.
Statement 2: Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Nitrogen cannot be utilized by phytoplankton as N2 so it must undergo nitrogen fixation which is performed predominately by cyanobacteria.
Statement 3: Ammonia and urea are released into the water by excretion from plankton. Nitrogen sources are removed from the euphotic zone by the downward movement of the organic matter. This can occur from sinking of phytoplankton, vertical mixing etc.
Bacteria are able to convert ammonia to nitrite and nitrate but they are inhibited by light so this must occur below the euphotic zone.