Macro Algae chlorophyll spectrum

[Mr. Wiggles]

Hi RC,

I have been interested in the lighting spectrum for macroalgae, specifically for the chaeto algae used by many of us in refugiums. I see many different lights recommended from CFL, LED, and HPS and in color temps from 2700k to 6500k as well as horticulture red/blue leds. For me I find that my chaeto grows well for a period and then slows down and can eventually die off. Some of this is no doubt due to lower nutrients, but I don't think this is always the case.

In my tank my chaeto has slowed way down recently, and my nitrates and phosphate are probably low but I still have a bit of cyano and algae on the glass so I know there are nutrients there. I typically use a 13w 6500k CFL light which has probably been in use for ~5 months. I decided to try a quick experiment so I took some chaeto out and put it into a 2L soda bottle with new saltwater and then added NaNO3 (20ppm in nitrate) and K3PO4 (0.1 ppm in phosphate). So now there should be plenty of nutrients in the 2L bottle for the chaeto, added a little air pump for motion and areationso all I need is some light. I hooked up another 13w CFL, this one of unknown age and go no growth"¦.none. This got me thinking about the light and the necessary spectrum.

So I did some digging and found some papers about the chlorophyll composition and spectral characteristics of chaeto (#4) and other macro algaes shown belowThis seems to show that blue and red colors are of equal importance for the shallow water macros, while blue is more important for deeper water macros. In fact from the spectrum for chaeto, red light from 600-700nm seems to be a large component of the chlorophyll spectrum.


The table in this paper bears out this same assumptions with equal absorbance of blue and red. What I find to be interesting is that chaeto is dominated by chlorophyll a rather than chlorophyll b.


I think that we can start to draw some nice conclusions about the type and spectrum of light we should be using from this. Clearly we need blue and red but also some in the yellow region is also important. I saw on mlevsreef that now he is recommending using a 5000k led bulb. Mine just arrived and I am not lighting my fertilized 2L bottle with this light and am excited to see the results. I think the CFL bulbs lose intensity rapidly and might not be the best option unless you are changing them out regularly.
https://en.wikipedia.org/wiki/Compact_fluorescent_lamp

Here is the spectrum for the Cree 5000k LED bulb suggested on melevsreef:


I hope that this helps add to the discussion about macroalgae lighting!

 

[Subsea]

I am not so sure that I agree with you on the yellow spectrum.

In general, red & near red produce chlorophyll a & b. Blue and Royal blue also each produce chlorophyll a & b.

The color spectrum analysis graph is truely required to discuss lighting. With just a Kelvin color assigned to a lamp or a PAR reading, individual color spectrum is unknown. I use the 5K CFL with good results. From my point of view, heat is the only issue with that lamp.

 

[Subsea]

Sorry, I meant to include specific spectrum in above post.

Blues at 430nm produce chlorophyll A and at 460nm chlorophyll B is produced.

Reds at 660nm produce chlorophyll A and at 630nm produce chlorophyll B.


When light penetrates water, the different color spectrum are filtered out by their energy level. The shorter the wave length the higher the energy. This means that red light is filtered out in the first 15' of water depth.

For most of us on the hobby, we adjust the light to what is good for us to view.

 

[Mr. Wiggles]

Hi, and thanks for the response.

I agree about the chlorophylla/b max absorbancy values, and the fact that red light is filtered out first is completely correct. I often see people quote the chlorophylla/b values as well as the red/blue light discussion, but I never found anyone who actually looked at the spectral data for the actual chlorophylls and other pigments in algae.

As we know the chlorophyll is the major component of light harvesting pigments in plants, but there are a host of others as well. Curiously this paper describes a pigment in the deep water macros which absorbs green light! So while I agree that yellow isn't a major component of chorophyll a/b, in the shallow water macros the absorbancy increases from about 570nm-680nm. This is from yellow to red light which is why I mentioned it.

Just to clarify the caption for the spectra
Shallow water macros:
1) Monostroma nitidum 2) Ulva pertusa 3)Enteromorpha compressa 4) Chaetomorpha crassa 5) Cladophora sp.

The Deep water macros, which are more blue dependent but also have green and red absorbing pigments include:
6)Ulva japonica 7) Cladophora wrightiana 8) Valonia macrophysa 9) Codium adhaerens 10) Codium mamillosa 11)Codium fragile

I am trying to see if I can measure the specta from a series of different lights so that maybe we can start to rely less on the Kelvin numbers but talk about spectrum in a real, quantifiable way.

 

[Subsea]

As a hands on type of person while pursuing best lighting spectrum for two deep water red macros, red grapes and dragons breath, I focused on at what vertical depth these macros were collected at.

According to Russ Krownwetter, diver owner if Gulf Coast EcoSystem
Botryocladia is collected in 15'-130'
Halmenia Floridina is collected in 30'-130'

Considering that these two macros have been grown successfully under varied lighting spectrum, I would say that some if not many macro were photoadaptable to spectrum.

 

[Devaji108]

^ thats good to know.so does your Marco need both a&B? I am guessing it does.
if your light does not have reds but whites in the 8 to 12K plus blues in the 445 and 460 rage would one be able to grow both deep water and shallow?

this is something that has been on my mind for a few months now..
of course this is all theoretical as the tank is yet to be set up.

 

[Subsea]

^ thats good to know.so does your Marco need both a&B? I am guessing it does.
if your light does not have reds but whites in the 8 to 12K plus blues in the 445 and 460 rage would one be able to grow both deep water and shallow?

this is something that has been on my mind for a few months now..
of course this is all theoretical as the tank is yet to be set up.

I think that macro needs both Chlorophyll A & B. While I am weak on LED technology, in general, a white LED is composed of red, green and blue.

As a rule, most shallow water macro grow faster than deep water macros. If your tank is a display, the faster growing macro will outcompete the slower when nutrients are high.