1. Limnology!

2. Limnology “the oceanography of lakes”
Study of the functional relationships and productivity of freshwater communities, as they are regulated by the dynamics of their physical, chemical, and biotic environments

3. Limnology
Term “limnology” derived from Greek word “limne” meaning pool, marsh, or lake
The science arose from from lake investigation
mid-1800s - Henry David Thoreau’s observations from Walden Pond (nice lake)

4. Limnology Gradually grew to encompass all inland waters
Today includes standing water (lentic habitats) as well as running water (lotic habitats)

5. Physical Limnology
Unique properties of water - important role in penetration, distribution of light, heat
Water movements (waves, currents)
Geology of basin (origin, morphology, leaching minerals)

6. Chemical Limnology Inorganic , organic compounds
Closely allied to geology (leaching)
Distribution often related to water movements

7. Biological Limnology Base is photosynthesis - primary productivity
Regulated by, and may regulate, physical and chemical factors

8. Limnology Everything becomes interconnected
Add in further complications resulting from human relations and impacts
Very complicated science

9. Properties of Water
Unique characteristics of water regulate the chemical, physical, and metabolic activities in freshwater systems

10. Properties of Water
1) non-linear relationship between temperature and density
2) high specific heat
3) viscosity-density relationship
4) high surface tension

11. Structure of Water Molecule
3 atoms arranged into non-linear molecule
104.5° angle

12. Structure of Water Molecule
Polar molecule with weak charges
Allows for weak hydrogen bonding between adjacent water molecules

13. Structure of Water Molecule
Each water molecule can have hydrogen bonds with as many as 4 other water molecules

14. Structure of Water Molecule
Structure most obvious in ice
Creates tetrahedral pattern
Lots of space between molecules
Low density - it floats

15. Temperature-Density Non-linear Maximum density at 4°C
Lower density at higher and lower temperatures
Hydrogen bonding and molecular movement

16. Specific Heat Or heat capacity - high for water
Amount of heat energy required to raise unit mass 1°C
Because of hydrogen bonding

17. Specific Heat
Temperature changes occur more gradually in lakes than in terrestrial environs
Lakes can buffer climate of nearby land masses
Warmer in winter, cooler in summer

18. Viscosity-Density Relation
Viscosity - resistance to flow
Viscosity of water increases as density increases
It doubles as temp decreases from 25°C to 0°C

19. Viscosity-Density Relation
Change not apparent to human eye
Profound effect on movements of microscopic plants and animals, and sinking of particles in lakes

20. High Surface Tension
Hydrogen bonding interrupted at air-water interface
“molecules exert an inward adhesion to the liquid phase”
Molecules at surface resist being pulled apart

21. High Surface Tension
Allows objects that would normally sink in water to be supported on the surface
Mercury is the only liquid with a higher surface tension
Increases slightly with increased salinity, decreases with increased temperature, addition of organic compounds