The last type of a dead zone is a diel cycling dead zone. These dead zones occur in the warm/summer months but only during the night. This type of hypoxic condition happens in shallow waters that are rich with vegetation and phytoplankton. During the daytime, the water is not hypoxic because the plants are photosynthesizing and over saturating the water with oxygen. At night however, the plants stop producing oxygen and the rates plummet. Diel cycling hypoxia is occurs naturally to some extent but human and agricultural waste increases the effect of this condition. These changes in the water can be harmful to animals and may be removing them from these zones as well.