1. Lecture goal: To identify and describe the properties of water that are most important to understanding broader patterns of habitat structure and ecology in freshwater systems. Properties and behavior of H 2 0 1: The specifics

2. Molecular Structure Density Temperature Oxygen Light

3. The Specifics Molecular Structure Density Temperature Oxygen Light

4. Structure of H 2 O Polarity Solvent properties

6. Surface Tension

8. The Specifics Molecular Structure Density Temperature Oxygen Light

9. Temperature and Water Density

10. Anchor Ice

11. Depth and Water Density Density increases with depth. Influenced by atmospheric pressure and other factors.

12. Salinity and Water Density Density (g / ml) Freezing point of sea water (35 g/L) = -2ºC Max density of sea water = -2ºC Salinity of “Freshwater” ranges from 0.01 – 1.0 g/L Saline lake  60 g/L

13. The Specifics Molecular Structure Density Temperature Oxygen Light

14. Temperature and Water Density

15. Specific Heat of Water Specific heat: amount of heat in calories required to raise a unit (i.e., a gram) of the substance by 1  C. Specific heat of water = 1 Latent heat of fusion = 80 Latent heat of vaporization = 540

16. Measuring Water Temperature Standard / immediate temperature Seasonal max, min, mean Degree days

17. The Specifics Molecular Structure Density Temperature Oxygen Light

18. How oxygen gets into water

19. How oxygen gets into water…or not

20. Pressure and O 2 Solubility

21. Temperature and O 2 Solubility Oxygen Solubility (mg / L)

22. Salinity and O 2 Solubility

23. Oxygen Terminology Saturation or Equilibrium Concentration Amount of DO that can be held by water in equilibrium with the atmosphere at a particular temperature, pressure, and salinity. Supersaturation Anoxia Hypoxia

24. The Specifics Molecular Structure Density Temperature Oxygen Light

25. Why is light important in aquatic systems? Light is energy, capable of work and being transformed from one form to another. Radiant energy of light transformed to potential energy by biochemical reactions (e.g., photosynthesis). Light provides the majority of energy input to aquatic systems – but getting light INTO aquatic systems is tough.

26. More Blue More Red Frequency Wavelength

27. How do plants receive light energy? Quanta or photons at specific frequencies

28. Controls on light input: season and latitude

29. Controls on light input: direct solar radiation

30. Other controls on direct solar radiation Time of day Altitude Meteorological conditions Topography

31. Controls on light input: indirect solar radiation

32. Controls on indirect solar radiation Scattering through atmosphere Solar height

33. Controls on light input: reflectivity

34. Controls on reflectivity Angle of incidence Surrounding topography Surface conditions of water

35. Albedo Ratio of reflected to incident irradiance Increases with reflection at surface and scattering within the lake.

36. Albedo

37. Light scattering within lakes

38. Effect of Salinity on Density and O 2 Solubility Density (g / ml) Anthropogenic Salinization