[Coral-List] NH4 and bleaching

Angus Macdonald angus at ori.org.za
Wed Jan 4 01:47:26 EST 2006

Dear coral-listers, 


Thanks to everyone for their input on NH4 in aquaria and coral health. I was
mistaken in my initial question as 20 ppm is way too high, 0.20 ppm would
have been in the right ballpark, I think.


I have one more question to put to those interested. If levels around 20µM
have shown increased densities of zoox (Pac Sci: 48:273-283), the
combination of high NH4, higher than normal light and temperatures might
exacerbate a bleaching cycle. This is makes sense if: mode of bleaching
occurs when the host cell detaches (Biol Bull 182:324-332) and light and
temperature induce oxidative stress (Free Radical Bio Med 33:533-543). 


Please bear in mind these are the most recent or key papers and not
comprehensive lists. Obviously this would require more justification.
However, in a tank system with limited temperature control, it might be wise
to assume levels of NH4 should be kept within the 1-5µM range to keep coral
from bleaching?    


Angus Macdonald


Oceanographic Research Institute

uShaka Marine World

Point Road


(031) 328 8168


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