New study in Nature magazine: Higher phosphates help corals avoid bleaching

[Squidmotron]

You can read the simplest summary here on Advanced Aquarist: http://www.advancedaquarist.com/blog/elevated-phosphate-reduces-coral-bleaching

The gist of the experiment this: the presence of abundant phosphates in the water can keep coral from jettisoning zooxanthallae in situations that might otherwise cause bleaching.

In this particular experiment, that situation was high temperatures (going up to 86 degrees). But, it may be applicable to other events that can cause bleaching as well.

[DivingTheWorld]

It's an interesting article but it seemed to leave out the most important part: what are the levels? In reef aquaria we usually to keep Phosphate low 0.01-0.03. But does that represent a "high" amount in nature?

[Tripod1404]

From the nature article
It has also been demonstrated in recent studies26,51, in which changes in seawater nutrient ratios induced changes in carbon acquisition, translocation and allocation within the symbiosis. The benefits that the symbiotic association retrieves from a low N:P ratio condition are highlighted in our second experiment, in which the supplementation of seawater with 2 μM phosphate, and the subsequent decrease in the N:P ratio, prevented bleaching, increased the photosynthetic capacities, the carbon translocation, as well as the carbon retained into animal biomass during thermal stress.

[Squidmotron]

It's an interesting article but it seemed to leave out the most important part: what are the levels? In reef aquaria we usually to keep Phosphate low 0.01-0.03. But does that represent a "high" amount in nature?

My impression was they elevated it a bit above regular ocean levels found in their natural environment, but I could not ascertain what the "higher" levels were.

[Squidmotron]

The benefits that the symbiotic association retrieves from a low N:P ratio condition are highlighted in our second experiment, in which the supplementation of seawater with 2 μM phosphate, and the subsequent decrease in the N:P ratio, prevented bleaching, increased the photosynthetic capacities, the carbon translocation, as well as the carbon retained into animal biomass during thermal stress.

I can see why they became scientists instead of writers.

[Mr. Wiggles]

Not sure what the issue is, the concentration is given in the quote: 2 μM phosphate.

Some quick math converts the 2 μM to about 0.2 ppm PO4.

[Squidmotron]

I was told there would be no math.

[Tripod1404]

Mr. Wiggles you are right. For the ones who are interested in the math;

Lets assume conversion rate of phosphorus (P) to phosphate (PO4) is 1 to 1 since 1 PO4 molecule is 1 P plus 2 O2 molecules .

1M = 1 mol/L

2 μM = 0.000002 M

0.000002 M = 0.000002 mol/L

molecular weight of phosphate is ~95 g/mol

so;

0.000002 mol/L X 95 g/mol = 0.00019 g/L = 0.19mg/L = 0.19 ppm


Level of phosphate in ocean surface is given as 0.005 ppm
http://reefkeeping.com/issues/2004-05/rhf/

but liveaquaria gives the level in coral reefs as 0.13 ppm
http://www.liveaquaria.com/PIC/article.cfm?aid=89

So depending on which value is true or where the seawater was taken from, effective phosphate concentration they used can be;

0.195 ppm or 0.32 ppm

[Squidmotron]

That's actually seems a pretty substantive number.

[Breadman03]

I was told there would be no math.

I was also told that I wouldn't have a calculator with me everywhere I went. :)

Back on topic, this concurs with what many carbon dosers have learned: nutrients that are too low bleach out corals and elevated nutrients result in high zoox concentrations that result in a brown appearance.

[JZinCO]

I was also told that I wouldn't have a calculator with me everywhere I went. :)

Back on topic, this concurs with what many carbon dosers have learned: nutrients that are too low bleach out corals and elevated nutrients result in high zoox concentrations that result in a brown appearance.

If I can rephrase because I think you left out an important caveat: When the species of coral under this study were under thermal stress, coral under high phosphate water avoided bleaching through increased phosphate uptake. These coral were significantly less bleached than under low phosphate conditions. When no thermal stress is present, phosphate levels do not matter.

Not sure what the issue is, the concentration is given in the quote: 2 μM phosphate.

Some quick math converts the 2 μM to about 0.2 ppm PO4.
winner winner

[Subsea]

Interesting that thermal stress resulting in bleaching of coral was avoided due to higher phosphate uptake.

Twenty years ago, industrial wastewater research showed that when aerobic bacteria were stressed with low oxygen, these bacteria up took and maintained higher phosphate concentrations.

[HippieSmell]

Interesting that thermal stress resulting in bleaching of coral was avoided due to higher phosphate uptake.

Twenty years ago, industrial wastewater research showed that when aerobic bacteria were stressed with low oxygen, these bacteria up took and maintained higher phosphate concentrations.
So, you think maybe the issue isn't temperature, but lower dissolved oxygen due to higher temperature?

This leads me to a question. How far from saturation are oxygen levels in a tank and in the ocean?

[Timfish]

I can't say I'm surprised. This paper on nutrient imbalance (http://www.indiaenvironmentportal.org.in/files/file/Nutrient%20enrichment.pdf) showed an internal PO4 level below .07 mg/l could cause corals to be very susceptible to bleaching. Only a tiny fraction of reefs have PO4 levels below .05 mg/l. The average is .13 mg/l and contrary to what is commonly believed surface PO4 levels can be .5 mg/l or higher (look at fig. 3 here (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.501.2065&rep=rep1&type=pdf))

[Subsea]

So, you think maybe the issue isn't temperature, but lower dissolved oxygen due to higher temperature?

This leads me to a question. How far from saturation are oxygen levels in a tank and in the ocean?



With respect to oxygen saturation levels in reef tanks, I can only say it depends on the tank. It is probably the least talked about parameter, yet, the most important.

Actually, I was alluding to the fact that the phosphate molecule has an important function in the biochemistry of reef inhabitants starting with the bacteria.