Entry+four

In the morning, the plants (lilly pads and other types of plants in the water) are releasing carbon dioxide and giving oxygen for the fish and turtles to breath. The plants are also in the process of cellular respiration. So the also take in oxygen and give off carbon dioxide. But the net product of oxygen released is greater than the loss. While the plants are giving off oxygen, the organisms (fish, turtles, other organisms in the pond)) inside of the pond are taking that oxygen in and releasing carbon dioxide.

At night, both the plants and the organisms (fish, turtles, others organisms in the pond) are taking in oxygen, and releasing carbon dioxide (cellular respiration).

This cycle repeats itself over and over again.