Final answer:
A significant contributor to thermal pollution in power plants is the discharge of cooling water that has been used to cool the plant's systems and is then released into natural bodies of water at a higher temperature.
Step-by-step explanation:
In a power plant, a large factor in the creation of thermal pollution is cooling water discharges. Thermal pollution is a form of pollution that occurs when water used as a coolant in power plants is returned to a natural body of water at a higher temperature, leading to various environmental issues. The warm water released is less oxygenated, causing stress on the aquatic ecosystem as the hotter temperature affects dissolved oxygen levels and can harm or kill cold-blooded organisms.