Which factors can influence Dissolved Oxygen (DO) levels in water?

Dissolved Oxygen (DO) levels in water are influenced by multiple environmental factors, and the most comprehensive answer includes water temperature, salinity, and atmospheric pressure.

Water temperature affects the solubility of oxygen; as temperature increases, the capacity of water to hold oxygen decreases. This relationship is critical, as warmer water holds less dissolved oxygen, impacting aquatic life that relies on it.

Salinity also plays a significant role in DO levels. Increased salinity reduces the amount of oxygen that water can hold. In aquatic environments, this is particularly relevant as variations in salinity can occur, such as in estuarine systems where freshwater mixes with saltwater.

Atmospheric pressure influences the amount of oxygen that can dissolve in water. Higher atmospheric pressure increases the pressure of gases above the water surface, allowing more oxygen to dissolve. Conversely, lower atmospheric pressure can lead to decreased dissolved oxygen levels, which can affect aquatic organisms that depend on this oxygen for survival.

By considering all three factors—temperature, salinity, and atmospheric pressure—the answer correctly reflects the complexity of the factors that affect dissolved oxygen concentrations in aquatic systems.