Light Attenuation In Water Results From 5 Regional

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: mmol quanta m 2 s-1 (m. E)

Light Calculations • Exponential Decay – Beer’s Law – Compute Ln(Iz) and regress to get slope – Slope = attenuation coefficient, k [m-1] • Secchi Disk Iz = I 0 e - kz

Light Attenuation: Wolf Lake • k = 0. 477 m-1 • Secchi: 4. 9 m • Overcast, rain, windy • Pristine but w/ high DOC content

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)

Light Attenuation: Green Lake • k = 0. 174 m-1 • Secchi: 8 m • Sunny, slight breeze • Oligotrophic w/ high Ca. CO 3 content

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)

Light Attenuation: Oneida Lake • k = 1. 20 m-1 • Secchi: 2. 6 m • Conditions unknown (PAR measurements done separately) • Eutrophic (and shallow)

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…

Questions?