During the daytime, which process takes place that increases pH levels in the water?

The process that increases pH levels in the water during the daytime is photosynthesis. During photosynthesis, aquatic plants and algae take in carbon dioxide (CO2) from the water and release oxygen (O2) as a byproduct. This uptake of CO2 reduces its concentration in the water, leading to a decrease in carbonic acid formation. As a result, the overall acidity of the water decreases, which in turn raises the pH level.

This increase in pH during the daytime can be significant, particularly in areas with abundant aquatic vegetation and sunlight, as photosynthesis occurs actively during daylight hours. The production of oxygen alongside the reduction of CO2 leads to a more alkaline environment in the water.

In contrast, respiration, which occurs continuously at all times, would not lead to an increase in pH as it involves the consumption of oxygen and release of CO2, which can lower pH. Algal blooms can also affect pH levels but are not a process that consistently happens throughout the day in the same way that photosynthesis does. Decomposition primarily involves the breakdown of organic material and can contribute to lowering pH through the release of acids. Thus, photosynthesis is the key process that directly correlates with increased pH levels