Dissolved Oxygen– The distribution and dynamics of
dissolved oxygen are important in aquatic systems because it controls the distribution, behavior, physiology, and growth of organisms.
– sources of O2: atmosphere & photosynthesis
– sinks: respiration & chemical oxidation
Properties of O2
• atmosphere ~ 21% O2; ~ 79% N2
• oxygen is more soluble in water than nitrogen
• solubility increases as temperature decreases
• equilibrium concentration increases with pressure
• solubility declines exponentially with increased salinity
Dimixis in Mountain Lake, Virginia
A. spring turnover
B. spring stratification
C. summer stratification
D. fall turnover
E. inverse stratification under winter ice
Distribution of O2 in Lakes
orthograde O2 profile
1. oligotrophic lakes: low nutrients & productivity
2. O2 regulated by physical means e.g. spring mixing
3. 100% saturation with depth
clinograde O2 profile
1. eutrophic lakes: high nutrients & productivity
2. loss of O2 through biological oxidation of organic matter
3. hypolimnetic O2 depleted after summer stratification
metalimnetic O2 maxima & minima
• Phytoplankton
• Zooplankton
