The temperature of an aquatic ecosystem is of great importance because it can influence:
Since cold water can hold more dissolved oxygen than warm water, one of the
man-made problems associated with water quality is thermal pollution. Thermal
pollution is the introduction of warm water or other substrates into an aquatic
ecosystem. Sources include industries such as power plants and also storm-drain
runoff which has been warmed on streets, parking lots and sidewalks.
In addition, human activities such as cutting down trees, the removal of vegetation around the water, and construction can lead to an increase in water temperature. These practices result in an increase in erosion which leads to an increase in dissolved solids in the water. As dissolved solids increase, the water becomes turbid (less clear) or cloudy which allows the absorption of the sun's rays which increases the water temperature.
Increases in temperature also cause changes in aquatic plants and animals. As the temperature increases, the rate of photosynthesis increases. At temperatures above 32 degrees Celsius, the rate of photosynthesis will start to level off and then begin to decrease as the temperature continues to increase. As photosynthesis increases, the number of aquatic plants increase. This can lead to an increase in the number of plants which die and are decomposed by aerobic bacteria which consume oxygen in the process.
Increases in temperature also increase the metabolic rate of organisms which live in aquatic ecosystems. As the metabolic rate increases, the demand for dissolved oxygen increases and the rate at which the organisms go through their life cycles increases. As their life cycle rate increases, they may not be available as a food source at specific times as needed by many migratory species.