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

Background Light comes from the sun Plants use it for photosynthesis Temperature of water is regulated by sunlight Photosynthetically Active Radiation (400-700nm) quanta/area/time “photons”

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

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

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

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

Secchi Depth

Light Intensity

Light Extinction