Question

One dry so many large numbers of fish suddenly died in the shallow river. Which is the best explanation for Fishkill?

a) The water became warm, lowering the dissolved oxygen for the fish.
b) Heavy rains washed soil into the river, making it too muddy for the fish.
c) Nutrient-rich waters caused too many algae to grow, and the fish died from overeating.
d) The water became too cold, stressing the fish, causing them to become sick and die.

Answer 1

The best explanation for the sudden fish kill in a shallow river is due to thermal pollution causing the water to become warm and lower the dissolved oxygen levels, making it difficult for fish to survive.

Step-by-step explanation:

One of the primary reasons for a large number of fish suddenly dying in a shallow river is attributed to the decrease in dissolved oxygen levels in the water. This is often caused by thermal pollution, where the water temperature rises, thus reducing the solubility of oxygen. One such occurrence is a result of industrial activities that discharge warmer water back into the environment, like in power plants.

As the water temperature increases, the oxygen solubility decreases, leading to an oxygen-depleted environment. Aquatic organisms, especially fish, that require this dissolved oxygen, may suffocate if the concentration drops too low. Additionally, an increase in nutrients, such as phosphorus and nitrogen due to fertilizer runoff or sewage, can lead to algal blooms. When these algae die and decay, they also reduce the dissolved oxygen content, further contributing to fish kill events.

The correct answer to the student’s question about the mass fish kill is: a) The water became warm, lowering the dissolved oxygen for the fish.