Which statement correctly describes thermal pollution and its common sources?

• A. Elevated water temperatures have no effect on dissolved oxygen or aquatic life.
• B. Elevated water temperatures reduce dissolved oxygen, increase metabolic stress, and can cause algal blooms or fish kills; common sources are power plant cooling water discharges and hot industrial process water.
• C. Thermal pollution only occurs in marine environments.
• D. Thermal pollution improves metabolic performance for all aquatic species.

Answer: (B)

Thermal pollution raises water temperature, which directly affects how much oxygen water can hold and how aquatic organisms use it. Warmer water dissolves less oxygen, so dissolved oxygen levels drop; at the same time, organisms’ metabolic rates increase with higher temperatures, raising their oxygen demand and stressing fish and invertebrates. This combination can push ecosystems toward hypoxia, making conditions favorable for algal blooms when nutrients are present, and potentially causing fish kills as oxygen becomes scarce and stress increases.

Common sources of this pollution are cooling water discharged from power plants and hot water from industrial processes, which release warmed water back into nearby rivers, lakes, or coastal areas.

So, the statement is correct because it captures the moisture-oxygen relationship, the stress on aquatic life, the potential for algal blooms and fish kills, and identifies plausible sources. The other ideas don’t fit: elevated temperatures do affect dissolved oxygen and biology; thermal pollution occurs in both freshwater and marine environments; and warming does not improve metabolic performance for all species.