What will happen to producer popultions if the nitrogen cycle is disrupted

Scientists have determined that humans are disrupting the nitrogen cycle by altering the amount of nitrogen that is stored in the biosphere. The chief culprit is fossil fuel combustion, which releases nitric oxides into the air that combine with other elements to form smog and acid rain.

well for one plants are always the producer, so a is the answer. a wolf is more of the consumer(predator) and the deer is the prey so i know those two are out of the question. also mushrooms are fungi/fungus so a is the producer.