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Re: Algae and Incandescent Lighting
On Wed, 29 Nov 2000 18:49:51 -0600, Tom Wood <tomwood2 at flash_net> wrote:
> Matt, aka, Crimson2 at home_com has related his experience with algae and
> incandescent lighting. The Dennerle company has literature that corroborates
> Matt's experience. Dennerle claims that algae prefers lighting with a blue
> spike while plants prefer lighting with a red spike in the spectrum.
> Incandescent lights are high in red and low in blue, at around 3000K.
Diana Walstad would seem to concur. In _Ecology of the Planted Aquarium_,
"Q: I was told that there is a certain type of fluorescent light that is better for
plants than algae. Is there any evidence for algae requiring a different light
spectrum than plants?
"A: No. Many algae readily adapt to light spectral changes, probably more so
than plants. However, full-spectrum light, which usually has a fair amount of
blue light, may stimulate algal growth more than light sources with less blue light
(e.g. 'cool-white' fluorescent, *incandescent* light, and high pressure sodium
lamps). THIS IS BECAUSE BLUE LIGHT MAKES IRON IN THE WATER
MORE AVAILABLE TO THE ALGAE, THEREBY STIMULATING ITS
GROWTH (see page 168)."
--- p. 162; "*" and CAPS emphasis added; no shouting intended :) -db
"Different investigators demonstrated iron photoreduction using a variety of light
sources ('cool-white', 'daylight' and 'vita-lite' fluorescent bulbs as well as
sunlight). However, UV and blue light induce the most photoreduction, because
only wavelengths below about 500 nm are energetic enough to break the
chemical bonds  (5)."
Endnote  is a reference to Morel, FMM (1983) _Principles of Aquatic
Chemistry_, p. 371
Footnote (5) says "The 280 to 400 nm portion of the light energy spectrum
encompasses UV (ultraviolet) light, while the 400 to 500 nm range consists of
violet and blue light..."
--- p. 168
On a personal note, I'm a little saddened to think 6700°K CFs, whose spectrum I
prefer on esthetic grounds, may end up giving algae a better chance in life.