We now have the possibility to simulate the natural lighting conditions present at a certain moment at a certain place at a certain depth and imitate it a certain depth in the aquarium. What we can't do is mimic the light intensity difference. If we simulate the light intensity at 5 meters sea depth in a 1 meter deep aquarium at a depth of 0.5 m with 20000 lumens, then +-17000 lumens remains on the bottom only 0.5m deeper or as much as at 10 meters sea depth. A coral that grows in the sea at a depth of 10 meters and reaches a height of 0.5 meters receives about 5% less light at the bottom than at the top. We cannot simulate that. As a result, a coral that grows up in captivity will take on a shape other than its natural. ref:
MB verlichting
PAR is not the same as PPF (photosynthetic photon flux or
Photosynthetically Active Photon Flux Density ) taking in account the color temperature.
One must take into account the different light-sensitive color pigments produced by the symbiodinium to absorb photons within a certain color spectrum. And that is not just blue light in what appears to us as a bluish environment . The bluish light of a certain depth must consist of the correct color spectrum so that all the color pigments can be used to the maximum. Measuring PAR of a lamp that emits light in one particular light color or spectrum is therefore of little use in my opinion.
Too much light occurs regularly in nature and coral symbiodinium has built in natural defenses for this, but it is rare in nature that these conditions last too long. More sensitive corals will be on the southwest or southeast side of the reef or grow up at greater depths using different color spectrums. Some types of corals are able to live in very different light conditions, which does not mean that they adapt easily if they are suddenly subjected to different lighting conditions.
That is why the active photo-period is of great importance for corals kept in an aquarium and according to research it is sufficient that this period is approximately nine hours spread over the day of 12 hours. ref:
MB verlichting
Too much light slows down coral growth but must not be considered dangerous as long the photo-period is limited.
On the other hand too much light has shown to bleach corals. Continuous illumination (24 hours 150µEm²S) resulted in instant bleaching and dead. ref:
MB verlichting
Corals protect themselves against too much light, dinoflagellates have a xanthophyll cycle. In dinoflagellates, the xanthophyll cycle consists of the pigment diadinoxanthin, which is converted under high light conditions into dinoxanthin . ref:
MB Symbiose met algen Anthias 2020 Cyano are not able to do that and may be killed by intensive light. ref:
MB Cyanobacteriën CMF De Haes 2018-2019
you are right
