As salinity increases, what happens to Dissolved Oxygen levels?

As salinity increases, the levels of Dissolved Oxygen (DO) generally decrease. This phenomenon occurs because higher salinity can change the physical and chemical properties of water, including its ability to hold oxygen.

In freshwater, the solubility of oxygen is higher, whereas in saline water, the presence of salt ions affects the water's physical characteristics, leading to reduced oxygen solubility. Additionally, as salinity increases, the water density also increases, which can lead to stratification; this stratification can limit the mixing of water layers, leading to lower oxygen levels in deeper areas.

In aquatic environments, this decline in DO can be critical for aquatic life, as many organisms rely on adequate oxygen levels for survival. Therefore, as salinity rises, the decrease in Dissolved Oxygen poses challenges for the organisms inhabiting these waters, impacting the overall health and biodiversity of the ecosystem.