Oxygen is the number one necessity for life. In aquatic systems oxygen is found in the form of dissolved oxygen and without it, the fish, crabs, and oysters cannot exist. Low dissolved oxygen concentrations can lead to reduced growth and reproduction rates, change the distribution and behavior patterns of the aquatic organisms, and can lead to death.
Dissolved oxygen is measured in milligrams per liter (mg/l) and can enter the water through photosynthesis from aquatic grasses, phytoplankton, or algae and by the physical process of wind mixing. Dissolved oxygen concentrations are usually better on those days, or seasons, when there is greater wind mixing, however, the ecosystem quickly regresses back to being dominated by low dissolved oxygen in the absence of wind if nutrient levels are otherwise excessive.
South River Bottom Dissolved Oxygen
Dissolved oxygen concentrations of 5.0 mg/L or greater will allow marine creatures to live and thrive. 2mg/l or less is considered Hypoxic, and 0.2mg/l or less is considered anoxic. The oxygen requirements vary from species to species, the complexity of the species and where the animal resides in the South River. Worms and small clams living in the South River's muddy bottom, where oxygen levels are naturally low, only need dissolved oxygen concentrations of at least 1 mg/L. Fish, crabs and oysters that live or feed along the bottom require oxygen concentrations of 3 mg/l or greater, and spawning migratory fish, their eggs and larvae need up to 6 mg/l.
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