1. Michael Adriaansen & Rachel Habig December 7, 2005
Light
Michael Adriaansen
&
Rachel Habig
December 7, 2005

2. Background Light comes from the sun Plants use it for photosynthesis
Temperature of water is regulated by sunlight
Photosynthetically Active Radiation
( nm) quanta/area/time “photons”

3. Background 42% of solar radiation is absorbed and dissipated as heat
0.023% ends up being used for photosynthesis
Light attenuation is affected by
water absorption
Dissolved organic matter
Particulates
Chlorophyll

4. Parameters and Measurements
Secchi depth gives us an idea of how deep light penetrates into water column
Has been correlated to amount of Chlorophyll a
Light extinction coefficients tell us the total amount of light attenuated at a given depth
Only gives us Ktotal

5. Methods We measured the total attenuation at each depth
Light meter used to collect data
Correction used to standardize the data
Initial deck reading divided by deck reading at each depth to correct for differences in light reaching lake over time.
Light at each depth was multiplied by this correction factor to make readings comparable

6. Light Extinction Coefficients
Calculation using measurement from light meter
K= (lnI-lnIo)/(depth)
Depth is change in depth from initial reading to desired depth
The natural log of light intensity values is used because light attenuates exponentially in water, this helps makes graphs more readable

7. Secchi Depth

8. Light Intensity

9. Light Extinction