During which time of day are dissolved oxygen (DO) levels typically the lowest in a facultative pond?

Dissolved oxygen (DO) levels in a facultative pond are typically lowest during the night. This is primarily due to the absence of photosynthesis, which occurs during daylight hours. In the daytime, aquatic plants and algae are able to harness sunlight to produce oxygen as a byproduct of photosynthesis, thus increasing DO levels. However, when the sun sets, photosynthesis ceases, and the biological processes that consume oxygen for respiration continue. As the night progresses, these processes can deplete the available dissolved oxygen, leading to the lowest levels of DO occurring during this period.

Understanding this cycle is crucial for managing aquatic systems effectively, as low DO levels can significantly impact the health of aquatic organisms. The fluctuation of DO levels is influenced by multiple factors, including water temperature, organic load, and the presence of vegetation, but nighttime conditions are particularly influential due to the lack of photosynthetic activity.