What are two ways that oxygen levels in water become dangerous?

1. Decreased Dissolved Oxygen: Oxygen levels in water can become dangerous when oxygen becomes depleted due to a lack of water flow, high temperatures, and high concentrations of organic matter. When oxygen levels drop, aquatic species are deprived of oxygen and can die due to asphyxiation. 2. Increased Dissolved Oxygen: On the other hand, excessively high concentrations of dissolved oxygen can become toxic to aquatic organisms when the oxygen levels exceed their tolerance range. High oxygen levels can cause an imbalance in other water chemicals, leading to a decrease in pH or an increase in metals such as aluminum or iron. This can cause a decrease in populations of aquatic species and can also result in anoxia, where large areas of the water body become effectively devoid of oxygen.