Temperature
If you live in a fishing community, you might have observed that fisherfolk go fishing late in the afternoon or very early in the morning. This is because schools of fish usually stay ashore or on the water’s surface at such time to get enough supply of dissolved oxygen. Oxygen gas is actually soluble in water to the extent of 489 mL O2 in 100 mL of water at 0°C. An increase in temperature reduces the solubility of oxygen gas in water.
Fish usually stay away from the shore as the day becomes hotter; they move into deeper and cooler portions of the water for a better supply of dissolved oxygen. This suggests that as temperature increases, gases become less soluble. At a higher temperature, dissolved gases frequently bump into the liquid surface molecules and tend to be more volatile, thus, weakening the gas-liquid interaction. At this point, the very mobile gaseous molecules escape, reducing the solubility of gaseous molecules in liquids.
Aquatic animals in bodies of water like rivers and lakes are affected by change in temperatures. Biologists have found out that the increased temperatures in rivers and lakes cause the concentration of dissolved oxygen to decrease. In this condition, warm water in rivers and lakes can no longer support thriving living organisms.
The reduced solubility of oxygen gas in hot water is related to thermal pollution. An increase in the temperature of water also causes an increase in the metabolic processes of fishes. Their rate of metabolism doubles with every 10°C rise in temperature.
