just the photo periods. there was a study done that was posted several yrs back (sorry i don't recall whom it was) that stated coral growth (actual depositing of CaCO3) came during the dark hours, and their CaCO3 uptake from the water that was to be deposited happened after 3 hrs of lights (less then 3 hrs and you get no growth) and declined sharply after 5 hrs (longer then 5 hours minimal CaCO3 was taken in by the corals).
You may not see results because the calcification takes place in darkness, not when the photosynthesis is occurring. This is just assuming that the hottest part of the day is also the brightest.
At least this is what I see from the others.
yes but i don't recall the exacts on it but IIRC CaCO3 depositing (skeletal growth) started as soon as photosynthesis ceased, the length of time it took to 'lay down' the new skeleton was very different for different corals. some LPS were only a few hours while some SPS were 4-5 hrs. I've searched for the article several times the last few days with no luck but i believe it was by Eric Borneman.
I'm not sure where all of this came from (perhaps someone misunderstanding Eric or something else they read and passing along the info???) but you guys have been
grossly misinformed.
Calcification in corals is ALWAYS taking place and is SUBSTANTIALLY faster in the light (when there is photosynthesis) than in the dark in most corals. In fact, on average most corals calcify 2 - 3x as fast in the light as they do in the dark, and for some the difference is much larger.
The amount of time it takes for calcium (the story with inorganic carbon is more complex) to be taken from the water and deposited in the skeleton is on the order of a few minutes, not hours. It takes a few minutes, at most, for the calcium to actually be transported, but it is used immediately.
Reef-building corals are able to build reefs BECAUSE of the increased rates of calcification that is somehow achieved through symbiosis, and most of the daily calcification is done during the day (though nighttime calcification is still a decent portion of the total).
See Meibom et al., 2006 for a fuller discussion of the role of photoperiod in calcification. There is no circadian rhytm controlling calcification in corals (it would seem). Calcification is slow in the dark and fast in the light. It takes a few minutes to reach the fast rate of calcification in the light after the lights are switched on, but only a few minutes. It takes a few minutes to drop down to the low rate of dark calcification when the lights are switched off, but only a few minutes. Longer photoperiod increases the amount of time at the higher rate of calcification, and hence increases daily rates of calcification, and vice versa. There's no reason to think that switching lights on and off (6 on, 6 off, 6 on, 6 off, etc.) should have any impact on calcification or be different from a single photoperiod of equivalent time.
Does the study look at the need for the 'down time' as well? I've also seen studies that mention the 5 hour 'saturation point' for photosynthesis but I've never seen anything that discusses the importance (or lack thereof) of the non-photosynthetic period.
This is another bit of misunderstanding/misinformation that keeps getting passed along. Corals in nature reach peak photosynthesis after a few hours because the sun is dim in the morning. The light intensity increases through the morning hours until about noon when it maxes out (assuming no clouds). This has nothing to do with the physiology of the corals or zoox. and is a result simply of the fact that the light is dim in the morning, so can't max out photosynthesis.
If you cover a coral with a black box and take the box off at noon photosystem II is saturated (max. photosynthesis) in 10^-12 seconds--not several hours. Photosynthesis becomes light saturated due to light intensity and is essentially instantaneous (1 picosecond) so has nothing to do with photoperiod (unless you're looking at periods of time less than 1 picosecond).
And just to be clear, I don't want to seem as though I am being harsh towards anyone--my intent is merely to correct pervasive misinformation. I'm trying to stop that dead in its tracks
Chris
