This is because the solubility of oxygen in water decreases as pH increases. In other words, as the water becomes more basic, it can hold less oxygen.

This can have a number of negative effects on aquatic life, as oxygen is essential for respiration. Fish, for example, may become stressed or even die if the oxygen levels in the water are too low.

Increased pH can also lead to the formation of harmful algal blooms, as some types of algae thrive in high pH conditions. These blooms can produce toxins that can harm aquatic life and humans.

The relationship between pH and oxygen levels is a complex one, and there are a number of factors that can affect the solubility of oxygen in water. However, the general trend is that as pH increases, oxygen levels decrease. This can have a number of negative effects on aquatic life, and it is important to be aware of this relationship when managing water quality.