During the night, how does algae affect the pH of the water?

During the night, algae can cause a decrease in the pH of the water primarily due to the process of respiration. Algae and other aquatic plants typically perform photosynthesis during daylight, which consumes carbon dioxide (CO2) and can lead to an increase in pH. However, at night, photosynthesis ceases, and respiration prevails.

During respiration, algae take in oxygen and release carbon dioxide. The released carbon dioxide reacts with water to form carbonic acid, which contributes to a lowering of the pH level. This is a crucial aspect of aquatic ecosystems, where the balance between photosynthesis and respiration affects the overall chemical composition of the water. Hence, during the night, a significant increase in CO2 concentration due to respiration leads to a decrease in the pH level of the water.