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http://www.astro.virginia.edu/class/skrutskie/astr121/notes/

Energy Balance: Light and Heat. http://www.astro.virginia.edu/class/skrutskie/astr121/notes/. Light meter. Secchi disk. Kalff 2002. Energy Balance: Light and Heat. PAR: Photosynthetically-available radiation [radiation usable in photosynthesis]. Guildford et al. 2000.

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  1. Energy Balance: Light and Heat http://www.astro.virginia.edu/class/skrutskie/astr121/notes/

  2. Light meter Secchi disk

  3. Kalff 2002

  4. Energy Balance: Light and Heat

  5. PAR: Photosynthetically-available radiation [radiation usable in photosynthesis]

  6. Guildford et al. 2000

  7. Energy Balance for a Lake Absorption Direct solar radiation (QS) Indirect solar radiation (QH) Reflection (QR) (QW) (QA) (QW) = long-wave radiation radiated back into the atmosphere Upward scattering (QU) (QA) = long-wave radiation returning from the atmosphere Net Radiation Surplus = QS + QH + QA – QR – QU - QW At night: Net Radiation Surplus =QA - QW

  8. Dodds and Whiles 2010

  9. Percentage light transmission as a function of wavelength for • pure water, • a green alga, • a cyanobacterium and • humic substances. • Water absorbs much of the red light, green algae transmit less green/blue and red, cyano-bacteria let even less blue and green light through, and humic substances remove blue and green light. • Thus, an oligotrophic lake has blue water, a lake with green algae appears green, a lake with cyanobacteria appears blue-green, and a lake with high levels of dissolved humic substances appears orange-brown. • Source: Dodds and Whiles 2010 (after data from Hakvoort 1994 and Wetzel 2001)

  10. Illustration of the appearance of colored objects at depths in lakes of different trophic status. Upper left - full light Upper right - a blue filter simulating light deep in an oligotrophic lake where white looks blue and blue looks black. Lower left - a green filter at moderate depth in a mesotrophic lake where white looks green and blue looks black. Lower right - a red filter at shallow depth in a eutrophic lake where the contrast between red and white is strongly decreased. Source: Dodds and Whiles 2010

  11. Payne, 1986

  12. Payne, 1986

  13. DOM [gelbstoff] Effects of dissolved and suspended matter on absorption of light at various wavelengths

  14. Osborne 2000

  15. Orthograde oxygen curve Clinograde oxygen curve

  16. Payne (1986)

  17. Start of the rainy season (cool/windy)

  18. Daily thermocline Seasonal thermocline Payne (1986)

  19. Osborne 2000

  20. Osborne 2000

  21. Osborne 2000

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