Question

how can aquatic life impact dissolved oxygen levels in water?
they increase water temperature.
they consume dissolved oxygen.
they increase oxygen levels.
they cause the water to cool.

Explanation:

Aquatic life, like fish, respire. Respiration involves taking in oxygen. In water, they consume the dissolved oxygen present. This directly impacts the dissolved oxygen levels in water. Option A (increasing water temperature) is more related to external factors like sunlight or industrial waste rather than aquatic life's direct impact on oxygen levels. Option C (increasing oxygen levels) is incorrect as aquatic life consumes oxygen (through respiration) not increases it (plants in water produce oxygen via photosynthesis but the question is about aquatic life in general which includes animals that consume oxygen). Option D (causing water to cool) is not relevant to the impact on dissolved oxygen levels.

Answer:

B. They consume dissolved oxygen.