Light saturation photosynthesis in coral

[LEGACYLINE]

I have been reading articles from Dana riddle lately and have a few questions on peak lighting hours I use t5 lighting ( ATI dimmable) my photo period is 10 hours but only 2 of those hours are at 100% the rest is ramping up or down ..par levels at peak hours are 350 up top 200 bottom give or take a little user error ..I know coral can reach max photosynthesis around 300-400 par so would 8 hours be better for growth at a steady par at those levels ? or would only a couple hours at that par level and ramping up and down be better having different par levels through the day? So basically do the corals photosythesise the full 8 hours at a higher par or do they shut down half the day ?

 

[biophilia]

I've been on a similar path lately with the Dana Riddle articles.. and came across this paper which might be of interest (though it doesn't directly address your question about ramping up or down per se)

https://www.researchgate.net/profil...n-an-aquarium-setting-A-matter-of-photons.pdf

What the researchers found with the stony coral Galaxea fascicularis was essentially that brighter or longer duration photoperiods had no influence on growth rate beyond what was essentially a medium level of light (150 par) for 8 hours. Higher light for longer photo-periods resulted in hourly zooxanthallae photosynthesis rates that were lower than those at the medium light/8 hour so the net result was essentially the same for all photoperiods in the study with the exception of the 24 hour light group which (no surprise) bleached and died)

It's just a guess, but I suspect that the specific photo period configuration and light level doesn't matter all that much providing you're not blasting them to the point of reaching photoinhibition or dipping below the 150-200 PAR found in intermediate-depth parts of wild reefs. Flow, stability, and nutrients -- including aspartic/amino acid availability as referenced in the paper -- possibly will influence growth rates more than any specific choice you make with lighting.

 

[LEGACYLINE]

Great article thanks , I have noticed that long peak hours the coral are all open and look great the first hour or so and the rest of the day they seem to open and close alot , seems to be a reaction trying to regulate how much light they are getting , with a small peak hour and ramp down they stay open with good polyp extension ( even the acropora react the same) so it's very interesting seeing how most everyone said acro need super high par levels I suppose different species differ though

 

[Randy Holmes-Farley Verified Community Expert]

I'll move this to the main forum.