1. Light and Temperature

2. Light photons- packets of electomagnetic energy wavelength: ultraviolet= short; infrared= long ~ 53% of the incident light/radiation is absorbed (transformed into heat) within the 1 st 1M of the water column shorter wavelengths penetrate deeper factors influencing incident radiation: latitude, season, time of day, altitude, & weather conditions

3. turbidity decreases water’s ability to transmit light –secchi disk –attenuation- reduction of light energy with depth by scattering & absorption

4. euphotic zone the stratum of water receiving adequate light such that photosynthesis exceeds respiration; primary production occurs here

5. Riparian Vegetation restricts incident light in woodland streams during the summer; max. illumination occurs in winter & early spring autochthonous -vs- allochthonous energy input

6. photosynthesis/respiration CO 2 + H 2 O ----> C 6 H 12 O 6 + O 2 radiation 400-700nm drives the system

7. Temperature absorption- the high specific heat of water permits the dissipation of light energy as heat; this process is enhanced by dissolved organic matter. The thermal conductivity of water is low therefore heat radiation is primarily a surface phenomenon.

8. In lentic systems, the transfer of heat to lower strata is primarily dependent upon mixing by wind action. As temperature increases and wind decreases thermal stratification increases; i.e. density differences of strata exceed the mixing power of the wind

9. Thermocline strata where the change in temperature is >1 o C/meter epilimnion- upper stratum characterized by uniformly warm water which constantly mixes metalimnion- characterized by thermal discontinuity hypolimnion- lowest stratification; temporally stable

10. Mixing Holomictic Lakes: complete mixing amictic- perennial ice cover; Antarctic lakes dimictic- two circulation periods; temperate lakes polymictic- frequent or continuous mixing Meromictic Lakes: strata separation chemocline

11. Thermal Stratification

12. Thermal Profile