PAR intensity vs time lights are on

[justingraham]

The Daily Light Integral (DLI) will determine the dosage of light, and better yet, we actually have some numbers to compare. The formula is simple:
Light intensity (micromole/m2/sec) x hours in photoperiod x60 mins/hour x60 secs/min = total number of photons/1,000,000. This requires a PAR meter of course. Extended photoperiod can make up for lower light intensity, but respect for minimum and maximum light intensities still apply.
http://www.advancedaquarist.com/2013/9/aafeature

Thanks for this

I just bought the apex par meter so I will be able to get all this information up to the minute and fine tune my lights.

But until then I would still like to understand tho so from my calculations I have a photo period of 7.5 Hours with my halides on and giving around 287 par at the middle of the tank

So the equation above I’m having trouble with can you write it out for me please

What I’m getting is 287 x 7.5 x 60 x 60 equals 7,749,000

Which I think is wrong but could be right

 

[oreo54]

so we divide by 1,000,000 to convert µmol to mol photons

7749000/1000000= 7.749

 

[justingraham]

7749000/1000000= 7.749

Ok so I was right except by dividing by 1 mill

 

[Dana Riddle]

Ok so I was right except by dividing by 1 mill

A DLI of 7 is common for aquarium corals. PAR (PPFD) of 250 should meet the requirements of just about any coral.

 

[TheEngineer]

In your article you separate out by wavelength and sum up based on their percentage of DLI. With our lights being heavily blue, do we need to make any adjustments?

 

[Dana Riddle]

In your article you separate out by wavelength and sum up based on their percentage of DLI. With our lights being heavily blue, do we need to make any adjustments?

I wish I had an easy answer. Different zooxanthella clades have differing light requirements and most likely generate protective xanthophyll pools in response to higher light intensities. Experimental evidence suggests this production is due to blue light, hence it is quite possible that blue light is not as effective. Now throw fluorescence into the mix (where blue light is fluoresced away)... I could go on. I think it was Ron Shimek that once said "Biological systems are difficult to predict - they do as they dang well please." Did this begin to answer your question, or have I over-thought it?

 

[TheEngineer]

Hmmm... ok. Then I have another question to add. Do we know what percent of blue light gets flouresced away? Is it the majority?

 

[Dana Riddle]

Hmmm... ok. Then I have another question to add. Do we know what percent of blue light gets flouresced away? Is it the majority?

I'm sure you've observed that some corals' color 'pop' (can't believe I used that term) more than others. This is due to yield, and yield is defined as the amount of light absorbed v. that fluoresced. If 40% of light absorbed is fluoresced, the Yield is 0.40. I would need to review the literature, but I think 40% is about as high as it gets - often much less. I can check this with the spectrometer and software and it could be that some corals (such as the orange Jack O'Lantern Pavona) could have a higher yield. But the real issue is if that fluorescence is useful in photosynthesis.

 

[TheEngineer]

That’s a great working point. It’s useful for photosynthesis? I was thinking flouresced light was “wasted”.

 

[Dana Riddle]

That’s a great working point. It’s useful for photosynthesis? I was thinking flouresced light was “wasted”.

It's a concept that has not been explored to my knowledge - Salih et al. stated the fluorescent/choromo- proteins act as photoprotectants. What if the fluorescence is within the absorption range of chlorophylls and/or peridinin? Some are!

 

[oreo54]

Thought that was studied in the deep water glow stuff...

Now, Wiedenmann thinks his team has the answer: the corals use a fluorescent protein to make the most of the small amount of light available in their habitats for photosynthesis. In other words, the deep-water corals and their shallow relatives fluoresce for opposite reasons.

Blue light is more useful for photosynthesis, but red light penetrates farther into coral tissues. So corals use a red fluorescent protein to convert the blue light into orange–red wavelengths. That means it reaches more of the organisms’ symbiotic algae, helping the corals to survive by making as much food as possible through photosynthesis. The researchers’ work is published in Proceedings of the Royal Society B[/quote]
http://www.nature.com/news/get-the-glow-the-secret-to-deep-water-corals-radiance-1.22259

 

[TheEngineer]

This subject always fascinates me. I love reading about it. This would seem to indicate, by my novice read of it, that our tendency to skew towards blue lighting is appropriate for both deep and shallow dwelling corals. But is that only limited to those corals with red pigmentation? Does the balance of chlorophylls and peridinin shift based on available light?

 

[Dana Riddle]

Let me expound on the fluorescence/photosynthesis thought. There are many fluorescent proteins with emissions in the range of absorption characteristics of photopigments. One in particular - called Keima - fluoresces at a maximum of 620nm.

Thought that was studied in the deep water glow stuff...

Wonderful - thank you! This ties in nicely with Salih's observations that corals fluorescing red are found in deeper/turbid waters or in shaded environments.

 

[Aztecaphoto]

Watch this video but Dana Riddle. It speaks to that.

Nice piece. Very helpfull as it changes the way I see ALK and coral grow. Thanks!