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Light Attenuation In Water

Light Attenuation In Water. Results From 5 Regional Lakes. Light Measurements (LI-COR). Scalar. Concerned w/ PAR Require both scalar (underwater) and cosine (surface) sensors Units: m mol quanta m -2 s -1 ( m E). Light Calculations. Exponential Decay Beer’s Law

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Light Attenuation In Water

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  1. Light Attenuation In Water Results From 5 Regional Lakes

  2. Light Measurements (LI-COR) Scalar • Concerned w/ PAR • Require both scalar (underwater) and cosine (surface) sensors • Units: mmol quanta m-2 s-1 (mE)

  3. Light Calculations • Exponential Decay • Beer’s Law • Compute Ln(Iz) and regress to get slope • Slope = attenuation coefficient, k [m-1] • Secchi Disk Iz = I0 e - kz

  4. Light Attenuation: Wolf Lake • k = 0.477 m-1 • Secchi: 4.9 m • Overcast, rain, windy • Pristine but w/ high DOC content

  5. Light Attenuation: Arbutis Lake • k = 0.891 m-1 • Secchi: 2.9 m • Heavy cloud cover, slight breeze • Slightly more ‘brackish’ than Wolf (visual speaking)

  6. Light Attenuation: Green Lake • k = 0.174 m-1 • Secchi: 8 m • Sunny, slight breeze • Oligotrophic w/ high CaCO3 content

  7. Light Attenuation: Onondaga Lake • k = 0.506 m-1 (?) • Secchi: 1.9 m • Overcast w/ moderate wind • Hypereutrophic (but does have its good days; i.e. clearing)

  8. Light Attenuation: Oneida Lake • k = 1.20 m-1 • Secchi: 2.6 m • Conditions unknown (PAR measurements done separately) • Eutrophic (and shallow)

  9. Light Summary: k, Secchi • Drivers: • Wolf/Arbutis: CDOM • Oneida: chlorophyll • light measurement and Secchi on different days • Onondaga: low k value doesn’t make sense but… • Green: Beautiful but boring…

  10. Questions?

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