Answer:
This question is incomplete as it does not contain the graphical representation of fishes population over time. The image containing this information has been attached in the attachment section.
The correct answer is D. The nitrogen from the fertilizer made the plants grow too quickly, which hurt the fish.
Explanation:
According to the attached image, artificial fertilizer is being used on a an apple orchard for six years. The orchard is located near a stream which runs out into a small bay.
Based on the results of the sampled population of fishes for five years as represented graphically by researchers (see attached image), it is obvious that the population of the fishes in the bay is reducing over the years. They also observed the growth of plantlike organisms in the bay.
The possible cause of this decline in the population of fishes is the increased growth of these plantlike organisms. The plantlike organisms are algae, which uses the nitrogen content of the artificial fertilizer that washes into the bay from the orchard, as a source of nutrient. This excessive nutrient causes the plantlike organisms to bloom or grow too rapidly- a process called EUTROPHICATION.
Eutrophication causes the oxygen content of the bay to reduce gradually as the blooming of the plantlike organisms depletes oxygen in the water body, thereby, harming aerobic aquatic organisms like fishes in the bay.
Hence, in a nutshell, the reduction in the population of fishes in the bay is as a result of the nitrogen from the fertilizer which made the plantlike organisms grow too quickly, leading to oxygen-depletion and subsequently death of the bay fishes.
