Warm water increases the metabolic rates of aquatic organisms. Warm water temperatures may keep some species from being able to reproduce. The removal of vegetation in the water causes more sunlight, which may increase its temperature drastically. Bacteria and other diseases grow faster in warm water, and susceptibility of aquatic organisms to disease in warm water increases as well. Thermal pollution, which is the discharge of large amounts of warm water from industrial plants, may cause increases in temperature.
Thermal pollution can also come from storm water running off streets, sidewalks, and parking lots.
Thermal shock can occur if the water temperature changes happen suddenly. Thermal pollution may disrupt the ecosystem balance in such a way as to eliminate heat intolerant species from an area. The tip of the thermometer needs to be at least 3-5 inches below the surface water. Warm water streams are very different from mountain or spring-fed streams that are generally cooler. Warm water streams should not exceed temperatures of 89 degrees F, and cold water streams should not exceed 68 degrees F. Summer heat can cause fish kills in ponds due to high temperatures reducing available oxygen in the water.