Question

"There is a farming community near the source of a river. This place was chosen because of its abundant water source and fertile land. As time passed, fish became less abundant in a nearby pond." What can you conclude about the depletion of fish in a nearby pond?

A) Fertilizer carried by runoff caused algae growth, which depleted oxygen.
B) Fertilizer carried by runoff clogged up the pond and prevented the flow of water.
C) Fertilizer carried by runoff depleted the water level of the pond.
D) Fertilizer carried by runoff provided too many nutrients to the fish.

Answer 1

The decrease in fish abundance is attributed to fertilizer runoff causing algal blooms, which deplete oxygen levels and create dead zones, making the water uninhabitable for fish.

Step-by-step explanation:

Regarding the depletion of fish in the nearby pond, the most likely conclusion is that fertilizer runoff has led to an excess of nutrients in the water, causing the rapid growth of algae, known as an algal bloom. Algal blooms deplete oxygen in the water when the algae die and decompose, creating an environment in which aquatic life, including fish, cannot survive. This process results in the creation of dead zones, areas with such low oxygen levels that aquatic organisms cannot sustain life. The direct impact of the excess nutrients, mainly nitrogen and phosphorus from the fertilizer, on ponds and lakes is a primary cause for concern, leading to the decrease in fish populations observed by the community.