Low Mg - what does it do to coral?

[Quah]

I'm curious as to what low Mg does to coral? Does it just cause issues with the carbonate cycle or are there health issues caused to coral from low Mg? I was having a discussion with a guy about his Duncans polyp bailing and he said low Mg and I suggested issues with ALK.

 

[Randy Holmes-Farley]

How low?

I've not seen much in the way of specific data.

Low magnesium might deter the growth of some corals and not others because the relative amount of magnesium in coral skeletons varies a lot. Coralline uses a lot of magnesium and might be harmed by low magnesium. Magnesium concentrations inside many cells is similar to the concentration in seawater, and if levels are very low and organisms are not adapted to actively taking it up, they might end up deficient inside cells too.

 

[Quah]

I can't say how low the Mg is. It was just a discussion we had at the LFS and I know it can impact the carbonate cycle and that can cause issues with corals but I just couldn't think of what Mg deficiency in and of itself does to corals.

 

[Randy Holmes-Farley]

I can't say how low the Mg is. It was just a discussion we had at the LFS and I know it can impact the carbonate cycle and that can cause issues with corals but I just couldn't think of what Mg deficiency in and of itself does to corals.

I too have not heard of a specific problem. It is also fairly unusual to actually have very low magnesium (but not to get a low and incorrect test result).