Redfield Ratio - significant factor in reef tanks?

[Reef_Hobbyist]

My understand is that this ratio is the relative concentrations of C, N and P found in natural seawater. "In dissolved organic material, nitrogen is about tenfold less prevalent than carbon, and phosphorus is several hundredfold lower in concentration than carbon."

C : N : P
I have seen this expressed as 1 : 0.1 : 0.01
I have also seen it expressed as 106 : 16 : 1

**which is interesting because these do not really match the description nor each other

For the most part I don't see a lot of reefers referring to this ratio although they may very well be achieving it (without specifically referring to it) by maintaining N and P levels in their tanks.

Randy, is this one of those things where although we know what the natural ocean levels are, it may not necessarily be a significant factor in a reef tank? I have seen some anecdotal evidence suggested by fellow reefers such as "when P higher than N it causes _____" or "my N and P levels can be higher than natural ocean levels and still have a great looking tank as long as the ratio is correct", etc, etc.

Is there science backing up the outcomes of when this ratio is off? Perhaps we just don't know?

 

[Randy Holmes-Farley]

The Redfield ratio, or any ratio like it, is the ratio of elements in various organisms. Exact ratios aside, all organisms have high C, less N and much less P that composes the organic molecules of their tissues. So in some sense, these are the ratios that photosynthetic organisms will be taking up out of the water (with some exceptions).

It is not, however, to be thought of as ratios of elements that should be in the water, and in the ocean, the available nutrients do not necessarily follow that ratio.

One implication of these ratios that many reefers encounter is that some nutrient export methods, such as growing macroalgae, take up a relatively fixed ratio (like a Redfield ratio) of N and P. And depending on what is in the water, the macroalgae may run out of available N or P before the other one runs out, leaving some of the other one in the water. In that case, dosing some nitrate or phosphate can actually make the other one decline if macroalgae growth increases.

 

[biom]

C:N: P ratio in different organisms

Redfield ratio 106:16:1 (phytoplankton)

bacterioplankton 32:6:1
coral tissue 155:24:1
zooxantellae in coral 365:21:1
copepoda (zooplankton) 30:3:1
Anchovy (fish) 20:5:1
You and me 18:3:1

 

[ksed]

Interesting, so correct me if I am wrong but bacterioplankton will take up more phosphate per ratio than phytoplankton. Therefore carbon dosing and encouraging bacterial growth might be more effective in an aquarium environment. Due to the fact that typically we introduce more phosphates than nitrates.

 

[Randy Holmes-Farley]

Interesting, so correct me if I am wrong but bacterioplankton will take up more phosphate per ratio than phytoplankton. Therefore carbon dosing and encouraging bacterial growth might be more effective in an aquarium environment. Due to the fact that typically we introduce more phosphates than nitrates.

More effective than what?

And why do you think we introduce more phosphate than nitrate?

 

[ksed]

Than macro algae which I believe is approximately the same as phytoplankton.

I've was under the impression that we add more phosphates through feeding .

 

[ksed]

Sorry Randy! What I am trying to do is compare carbon dosing (bacterioplankton) vs macro algae (phytoplankton).
By using the list above

 

[Randy Holmes-Farley]

One thing people need to be careful of is whether the numbers are weight based or atom (mole) based. P weighs 2.6 times as much as C, so the number ratios vary depending on the units.

According to this article,

https://web.archive.org/web/20040720161739/http:/www.botany.hawaii.edu/Bot482/Kaneohe Bay algae N-P Larned Mar Biol.pdf

the N : P weight based ratio of N : P for macroalgae ranges from 13:1 to 70:1.

A bigger issue is some of the organic carbon dosed to an aquarium likely ends up in N2 from denitrification. So the amount of N exported by organic carbon dosing may be disproportionally high relative to P. That seems to be what many people find.

As to more phosphate than nitrate coming from foods, I'm not sure why you'd say that. A tank with little nutrient export (like a fish only) might have on the order of 100 ppm nitrate and 1 ppm phosphate.

 

[ksed]

I thought it was the other way around. Learn something new everyday. I don't know why phosphate stuck in my head

Thanks a million Randy

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[JimWelsh]

C:N: P ratio in different organisms

Redfield ratio 106:16:1 (phytoplankton)

bacterioplankton 32:6:1
coral tissue 155:24:1
zooxantellae in coral 365:21:1
copepoda (zooplankton) 30:3:1
Anchovy (fish) 20:5:1
You and me 18:3:1

Source? Citation?

 

[biom]

Various sources, not really remember, collected over the time reading scientific papers, I'm trying to keep reefing as a hobby, not as part of my scientific work . If you are interested i'll try to find sources for at lest some of above mentioned.

 

[JimWelsh]

Sources would be nice, particularly that bacterioplankton one, but not really important. It's just those are nice numbers to have, and it would be great to be able to say I got them from somewhere authoritative, instead of just, "some dude on some forum said so".

 

[biom]

Are you saying i'm not authoritative? lol. I'm kidding.

Here it is:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC123973/

 

[Randy Holmes-Farley]

I

Are you saying i'm not authoritative? lol. I'm kidding.

Here it is:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC123973/

Interesting article!

One thing I find interesting is that the bacteria seem to be able to skew their composition to refllect the availability of N and P. So nitrogen-limited growth results in less N in them, and same for P.

It seems like that makes intuitive makes sense, but one has to wonder what chemicals they are adding or going without due to availability. I hadn't known individual cells responded that way.

That may partly explain why some people who begin dosing N or P find a bigger demand when first dosing than after the organisms have had their "fill".

 

[Habib(Salifert)]

I
flect

Interesting article!

One thing I find interesting is that the bacteria seem to be able to skew their composition to refllect the availability of N and P. So nitrogen-limited growth results in less N in them, and same for P.

It seems like that makes intuitive makes sense, but one has to wonder what chemicals they are adding or going without due to availability. I hadn't known individual cells responded that way.

That may partly explain why some people who begin dosing N or P find a bigger demand when first dosing than after the organisms have had their "fill".

Hi Randy

If you would have paid more attention back in 2006 on another forum...
Just joking.


"Besides the other comments, there are other sources for N besides nitrate. Such as ammonium and nitrite. For P, if the inorganic P is very low, they will use extracellular alkaline phosphatase to split organic phosphate esters.


Then there is "luxury uptake" in which the ratio get's skewed by the actual concentration of the nutrients in the water column. "

 

[Randy Holmes-Farley]

Hi Randy

If you would have paid more attention back in 2006 on another forum...
Just joking.


"Besides the other comments, there are other sources for N besides nitrate. Such as ammonium and nitrite. For P, if the inorganic P is very low, they will use extracellular alkaline phosphatase to split organic phosphate esters.


Then there is "luxury uptake" in which the ratio get's skewed by the actual concentration of the nutrients in the water column. "

Hey, Habib. Great to hear from you again!

 

[biom]

I
Interesting article!
One thing I find interesting is that the bacteria seem to be able to skew their composition to refllect the availability of N and P. So nitrogen-limited growth results in less N in them, and same for P.

Yea, in fact they do not change their composition per se, but probably change the kind of substances they are using as energy sources.

Hi Randy

If you would have paid more attention back in 2006 on another forum...
Just joking.
"Besides the other comments, there are other sources for N besides nitrate. Such as ammonium and nitrite. For P, if the inorganic P is very low, they will use extracellular alkaline phosphatase to split organic phosphate esters.
Then there is "luxury uptake" in which the ratio get's skewed by the actual concentration of the nutrients in the water column. "

Hi Habib, yes, there are many reasons why applying Redfield ratio (if we find it nessesery) in a closed system like reef tank is not that simple, because nitrogen is not only in form of nitrates, because the phosphorus is not only in form of phosphates and orthophosphates, and because N: P 16:1 is not equal to NO3: PO4 16:1 like many assumed, and many many others.

P.S. I really feel like i'm in time machine , it is great to have you both here.

 

[Myka]

It is not, however, to be thought of as ratios of elements that should be in the water, and in the ocean, the available nutrients do not necessarily follow that ratio.

Randy, are you at all implying that NO3 and PO4 may not be necessary for coral health? I don't think you're implying that, and there must be a certain amount of NO3 and PO4 that is needed in the water column for coral (and/or their symbiotic xoozanthellae) health, or do you think (or know) that corals utilize there nutrients from a source other than the water column?

and because N: P 16:1 is not equal to NO3: PO4 16:1 like many assumed, and many many others.

Yes! I've tried explaining this to people before and their eyes gloss over. Once you realize N does not equal NO3, and P does not equal PO4, then add to that not knowing if the particular ratio is using weight or atomic weight it gets pretty complicated for the average Joe Reefer!

 

[biom]

Hi Mindy, I know you expect answer from Randy, but just to give my 2 cents if you don’t mind.

Do you think (or know) that corals utilize there nutrients from a source other than the water column?

Yes, they do utilize nutrients from a source other than the water column, they are animals and they preferably utilize nutrients from their food – zooplankton, bacteria, phytoplankton, organic particles. But in the same time they are capable to utilize non organic nutrients like NH4, NO3 and PO4 from water column using active transport via cell membranes (but if both – organic and inorganic nutrients are present corals will prefer organic nutrients from food).

So in an ideal situation coral could survive in water containing zero nitrates and phosphates if there is enough food for corals. But in real world, even in healthy reefs this is not always the case (not even speaking about home reef tank) that’s why corals need some phosphates and nitrogen in form of NO3 (or preferably NH4) to be present in water to survive. In healthy reef this concentration of nutrients is enough to be as low as 0,02 for nitrates and less than .002 for phosphates, because there is plenty of diverse food for corals. We found with practice that in a reef tank we need about 10 times more nitrates and phosphates in water present (more than 0.2 ppm nitrates and about .03 ppm phosphates), because we simply cannot ensure enough quality food for corals.

Stoyan