Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What effect does thermal pollution have on aquatic ecosystems?

1. It increases oxygen levels in water

2. It disrupts gas exchange

3. It promotes algae growth

4. It decreases water temperature

The correct answer is: It disrupts gas exchange

Thermal pollution refers to the increase in water temperature due to human activities, such as industrial discharges and power generation. Elevated temperatures in aquatic ecosystems can significantly disrupt the natural balance of the environment. When the temperature of water rises, the ability of the water to hold dissolved gases, such as oxygen, decreases. This reduced oxygen concentration can lead to difficulties for aquatic organisms, particularly fish and invertebrates, which rely on oxygen for survival. Higher temperatures can also change the metabolism of these organisms, increasing their oxygen demand further, while simultaneously providing less oxygen in the water. This disruption in gas exchange can lead to stress or even mortality in sensitive species, contributing to diminished biodiversity and altered food webs within the ecosystem. While the other options relate to various ecological aspects, they do not accurately capture the primary impact of thermal pollution on gas exchange, making the correct choice particularly relevant to understanding how temperature increases affect aquatic life.