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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_, 
she wrote:

"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 [31] (5)." 

Endnote [31] 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 6700K CFs, whose spectrum I 
prefer on esthetic grounds, may end up giving algae a better chance in life.

David (B.)
Paris