Oct 2003

[andy-hipkiss]

Charles,

At this point, I would like to mention a pet “theory” of mine. One of the widespread “fads” in reef keeping today is the addition of phytoplankton cultures and other “foods” to reef aquaria. Often these are fed to tanks containing predominantly LPS corals in the belief that these coral will feed on this food. Observations are often made that the corals look much better and colorful after several weeks of such feedings. I would like to propose the theory that the benefit may not be so much from the actual ingestion of the food but the decomposition of the food leading to the generation of nitrogenous wastes which are then absorbed by the corals resulting in better pigmentation and increased zooxanthellae populations.

Is there an issue in terms of conclusions and pet theories in terms of the paper you summarise records both nitrogenous and phosphorus based fertilisers. Can we reach any conclusions from this? Perhaps the increased N is of advantage whereas the P is the opposite (or indeed vice versa) and one masks the dis-benefits of the other? Given the experience of commercial clam farmers, it's certainly very believable that increase N (prolly as NH4) is of benefit, but elevated P ??? ... hmmm

absorbed by the corals resulting in better pigmentation and increased zooxanthellae populations.

Is pigmentation held above the zoox?

 

[delbeek]

Andy: Sorry for the delay in replying.

Is there an issue in terms of conclusions and pet theories in terms of the paper you summarise records both nitrogenous and phosphorus based fertilisers.

I am not sure I understand your question.

If you look at the levels of P they are given in micromolar, the levels shown at the high nutrient site are still pretty low compared to what occurs in aquaria. So in nature, the elevate P may not be high enough to impact calcification but may be high enough to increase zooxanthellae number, whereas in aquaria with much higher P levels may be detrimental? I am thinking more in lines of nutrient benefits from elevated nitrogen that P.

Is pigmentation held above the zoox?

My understanding is that the pigments are located below the cell layer that contain zooxanthellae, I assuming this by the fact that when corals expel zooxanthellae, these pigments only then become noticable e.g. pinks, yellows, purples etc. Other pigments such as fluorescent ones may be held somewhere else. I don't know, I'd have to look it up.

Aloha!
Charles