Answer:
The correct answer is - a decrease in nitrogen compounds available to organisms.
Explanation:
Nitrogen fixation is the process that involves the atmospheric nitrogen and converts into a nitrogen compound that can easily be consumed by the organism as nitrogen is one of an essential part of life.
Nitrogen fixation is carried out by the microorganism like nitrogen-fixing bacteria like azotobactor. If these bacteria were destroyed then there will be a decrease in the nitrogen compounds that are consumed by the organism as there is no more nitrogen fixation takes place.
