Reefbreeders Fuge LED

gcarrol - energy absorbed does not equal energy entering the photosynthetic process.

I posted this last month in another thread, which summarizes the science behind using red light. In short, while you can achieve comparable growth rates with a range of bulb spectrums, red light is the most efficient.

 

I'm McLovin' this thread!

 

So are you saying we are only dealing with chlorophyll A when it comes to marine algae?

When you say comparable growth rates, what does that mean? I'm failing to understand why the same theory does not translate to terrestrial plants where blue light is used for growth.

Do red LEDs produce equal PAR to blue LEDs?

 

Have you ever added way too much red to your tank, and caused an increase in algae growth? I have noticed this trend, pretty much exclusively when the reds are overpowering the blues. However, when the blues out power the reds, the algae will stop, or slow in it s growth. While corals prefer more blue, and flourish in this light. Why? My theory is that most green algaes (emphasis on most) are very close to the waters surface in nature, chaeto will float in large chunks, it does not hang onto the rocks on the bottom of the ocean. Since water will rapidly absorb red light, most deeper water algaes are redish or brown, and prefer more blue light, take kelp for example, it anchors to the bottom, and is a deep brown-green color, while chaeto, which floats, is a lighter-mid green color. I have tried growing chaeto under regular reef lighting, and typically it does not do too well, even in a high nutrient system. So in my experience, red light has been much more effective at growing green algaes, phytoplankton as well.

 

ReefBreeders - for an explanation of your observation that red light can increase algae growth see below.

gcarrol:

1-
Marine algae contain many different pigments, but when it comes to growth/photosynthetic rates we are primarily concerned with chlorophylls a and b. The carotenoids play more of a protective role, they have little effect on growth. Chlorophylls a and b both absorb between 400-475 and 630-675. There isn’t a huge difference there.

2-
Growth rates are generally measured as an increase in biomass or # cells per unit time, or as specific growth rate, which relates to doubling time (the units are days^-1). The selected measurement depends on the species of interest. Specific growth rate is usually used for phytoplankton.

When I say comparable growth rates, I mean that it is possible to get a similar increase in biomass per unit time or specific growth rate with different spectrums, although one spectrum may waste more energy than the other. For example, green light isn't utilized much in photosynthesis, so most green photons would be reflected. How blue/red light change efficiency is explained in #3.

A quote from Carvalho et al. says the same thing:

“Full spectrum light is normally used for microalgal growth; however it has already been recognized that blue and red light are as efficient for photosynthesis as the full spectrum”.

In other words, as I said in my original post, different spectrums can lead to comparable growth rates.

3-
PAR, when measured as PPFR, is simply the number of photons a light sources emits between 400 - 700 nm per unit area per unit time. It is measured as umol photons/m^2/s. So I'm assuming you meant that as a trick question. 100 umol photons at 450 nm will result in the same PAR measurement as 100 umol photons at 670 nm.

Your reply to Reef Breeders, however, did not consider the energy difference between blue and red photons. Blue photons have more energy than red photons due to their shorter wavelength. This is proven by the equation: Energy = Plancks constant * speed of light/wavelength.

Photons less than 450 nm overexcite chlorophyll molecules, and energy must be shed before it can move onto the photochemical process. Much of the energy in a blue photon is wasted since the excess energy is dissipated as heat or fluorescence. This is my argument, and it is well supported by science. Using a “blue” LED less than 450 nm will waste energy. The energy required to excite the chlorophyll molecule to the ideal state equals the energy of a photon at 680 nm. Using lights with a lot of 680 nm photons minimize non-photochemical quenching (a fancy term for energy wasted as heat or fluorescence). This concept is explained on page 4 of the citation provided earlier.

4- Regarding terrestrial plants…
Marine algae captures energy more efficiently than terrestrial plants. This is just an educated guess, but perhaps blue light is used to grow terrestrial plants to provide them with more energy to make up for their lack of efficiency?

I’m a phytoplankton guy, not a tomato guy, but are you sure large amounts of blue light are used to grow terrestrial plants? I’m looking at the Kessil H350’s, which is used for horticulture and one model looks to be about a 50:50 red:blue split (magenta in color), while the other is mostly red. Kessil knows their stuff, so to me lights with a lot of red are pretty standard for terrestrial horticulture. Like I said in my original post, blue light can increase growth rates, but using a lot of red light is also necessary of optimizing growth is the goal.

5- Regarding blue light and microalgae…
Excessive light will cause photoinhibition, which can severely decrease growth. Blue light <450 nm is especially effective at causing photoinhibition since just a single photon is capable of overexciting the chlorophyll molecule. Overexcited chlorophylls can pass their energy on to oxygen, which produces reactive oxygen species (ROSs). I’m sure health nuts have heard of ROSs. They can severely damage the cell.

To drive home my point… a couple more quotes from Carvalho et al.:

“LEDs with a peak emmitance of 680 nm were used as sole light source of cultivation of Chorella vulgaris – with fourescent light being tested for comparative purposes. The narrow-spectrum monochromatic red light was found to reduce average cell volume from 60 to 30 um3 – although it did not affect total biomass production, as the number of cells produced was double.”

And referring to another study: Wang et al., 2007. Effects of using light-emitting diodes on the cultivation of Spirulina platensis. Biochem Eng J. 37, 21 – 25.

“In another study, LEDs with different wavelengths were used to grow Spirulina platensis under photoautotrophic conditions: higher light intensities generates more biomass, and the largest specific growth rate occurred with red LEDs – wheras blue LEDs the lowest biomass production values…”

So there you go, there is a lot of scientific evidence that supports the use of red LEDs to grow algae. Using red LEDs is at least as efficient as using broad spectrum lights (fluorescent lights, white LEDs).

 

Very nice.

+K to Jake for splainin' some science to us Rubes behind the Red / blue ratio(s) we're seeing increased chatter about lately!

 

+2 thats good info to have.

 

Yeah. What he said lol

 

Good info here guys, learning a lot. would like to long term follow up..

 

Jake,
Thanks for the detailed explanation. Unfortunately I am not like many of the sheep here that believe everything they are told. When someone posts a product is better than another product I would like to know why. Many times, manufacturers cannot answer my questions which for me raises a red flag. Sometimes the data is there some times it’s manufactured. I only question because I want to learn. Yes, even I still learn. No one in this hobby knows it all. I have never professed to be an expert on growing algae. This was the reason for the questions, not some trick as you might have thought. In fact, I do not employ growing algae for nutrient control on my own tank. I in turn, chose other filtration methods. Just because I don’t use it doesn’t mean I should not want to understand it. I am president of a fish club and am sometimes asked to speak to other clubs as well. I feel that if I don’t investigate products, how can I truly recommend them to my friends and fellow hobbyists who often come to me for advice.

Basically I feel you had a good understanding as to where I differed in opinion regarding the choice of the red spectrum. While blue packs more punch (Blue photons have more energy than red photons due to their shorter wavelength), algae processes red far more efficiently. This is the reason for choosing the red spectrum over blue. However it also seems that you are stopping short of saying that it is better than full spectrum lighting.

If you don’t mind I still have some more questions. Why use any blue at all? Also I have seen some talk of adding orange as well and what are your thoughts of that? Also wouldn’t it be possible to give the algae less blue light to prevent photoinhibition? Would it be possible to give them lower levels of blue light while still getting the same growth?