Redfield ratio as it pertains to the reef or your reef is stupid and pointless

[flampton]

This Redfield ratio thing always pops up on here and every other forum. For some reason many people have been convinced that it has something to do with reef tanks, let alone actual reefs.

The Redfield ratio is about the consistent molar ratio between carbon, nitrogen and phosphate of the deep ocean and the biomass of phytoplankton. The original proposal was a C:N: P of 106:16:1. Further research has pushed this to 163:22:1.

Now remember this is molar ratio. Not a ratio of parts per million. And thus you can see that most posts about the Redfield are already mistaken.

So for example you'll read someone saying how they want there nitrate to be 16 ppm and phosphate 1 ppm to keep it in line with the Redfield ratio. Yet this is actually 25 uM nitrogen and 1 uM phosphorus. Or a ratio of 25:1. Also for some reason everyone chooses to ignore the carbon part of the ratio. Not sure why, but I'm guessing it revolves around the fact that adding 106 ppm of organic carbon would probably be bad. (In a 50 gallon tank this would be like adding ~48 grams or a little bit greater than3 tablespoons of sugar.)

Anyways it really doesn't matter because the relationship between the deep ocean and phytoplankton has no bearing on the reef or the reef tank. The way to best show this to ask the question what does the reef actually look like? Well glad you asked. For example a recent paper looking at the Great Barrier Reef measured the respective nutrient levels at

Dissolved organic carbon - 83 umol
Dissolved inorganic nitrogen (ammonium/a/nitrate)- 0.26 umol
Dissolved inorganic phosphorus - 0.08 umol

For a ratio of 1038 : 3.25 : 1 (You'll see similar numbers when you look at other reefs.)

So yeah clearly not the Redfield. Oh and this number is a snapshot, not going to go too much into specifics but a reef's nutrients are in massive flux. Reefs are not deserts, there is just massive competition to internalize any little speck of usable C:N: P

There are many, many more reasons the Redfield has nothing to do with anything we do but hopefully the above is pretty clear already.

So please please retire the Redfield

Let me know below if you have any other questions, comments.

 

[blasterman]

Never bought it either.

Think about. The reason bigger tanks are so good at growing SPS is they have much greater and more stable volumes of trace levels of phosphate and nitrate while smaller tanks have more extreme yo yo effects. The ocean is taking this to the extreme. Far lower levels but a infinite amount.

We need better tools to stabilize nutrients. Redfield was an interesting discussion, but I agree it can be dismissed. Unlike calcium vs magnesium phosphate and nitrate arent transposed in biological channels because of their similiarity.

 

[minus9]

This Redfield ratio thing always pops up on here and every other forum. For some reason many people have been convinced that it has something to do with reef tanks, let alone actual reefs.

The Redfield ratio is about the consistent molar ratio between carbon, nitrogen and phosphate of the deep ocean and the biomass of phytoplankton. The original proposal was a C:N of 106:16:1. Further research has pushed this to 163:22:1.

Now remember this is molar ratio. Not a ratio of parts per million. And thus you can see that most posts about the Redfield are already mistaken.

So for example you'll read someone saying how they want there nitrate to be 16 ppm and phosphate 1 ppm to keep it in line with the Redfield ratio. Yet this is actually 25 uM nitrogen and 1 uM phosphorus. Or a ratio of 25:1. Also for some reason everyone chooses to ignore the carbon part of the ratio. Not sure why, but I'm guessing it revolves around the fact that adding 106 ppm of organic carbon would probably be bad. (In a 50 gallon tank this would be like adding ~48 grams or a little bit greater than3 tablespoons of sugar.)

Anyways it really doesn't matter because the relationship between the deep ocean and phytoplankton has no bearing on the reef or the reef tank. The way to best show this to ask the question what does the reef actually look like? Well glad you asked. For example a recent paper looking at the Great Barrier Reef measured the respective nutrient levels at

Dissolved organic carbon - 83 umol
Dissolved inorganic nitrogen (ammonium/a/nitrate)- 0.26 umol
Dissolved inorganic phosphorus - 0.08 umol

For a ratio of 1038 : 3.25 : 1 (You'll see similar numbers when you look at other reefs.)

So yeah clearly not the Redfield. Oh and this number is a snapshot, not going to go too much into specifics but a reef's nutrients are in massive flux. Reefs are not deserts, there is just massive competition to internalize any little speck of usable C:N

There are many, many more reasons the Redfield has nothing to do with anything we do but hopefully the above is pretty clear already.

So please please retire the Redfield

Let me know below if you have any other questions, comments.

Exactly! Funny, I mentioned that the Redfield ratio was pointless to our reef tanks on a live stream once and you would've thought I just told everyone to dump gasoline in their tanks. Nutrients can be a touchy subject for some people, especially for those that don't understand their importance and their relationship to each other, but as you mentioned, none of them ever mentioned anything about the first component of that equation, carbon. Our tanks are a "closed" system and as such, work on limitations. One tank could be nitrogen limited, the other phosphorus or carbon limited. These limitations can change through the life of the tank as the biology changes, whether it's from a lack of bacteria or diversity, fish, corals, etc. For me, it's always been observing these changes and adapting to them, instead of chasing numbers. Keeping ranges of N & P in relation to each other is so much better than chasing an exact ratio that has nothing to do with the zooxanthellae that reside within the coral we keep.

 

[brandon429]

I came for the title / and am staying for the clause above that says lack of bacteria in a reef tank

 

[zalick]

Thanks for the explanation! The "Redfield Ratio" has definitely become somewhat of an unchallenged gospel, much like 76 day fallow, without much challenge.

I appreciate you pointing out the errors and misconceptions!

 

[kenchilada]

The real problem isn’t Redfield, it’s stray voltage.

 

[taricha]

Fun thread. Let me drop this here for kicks. I got this idea that I could look at the cell CNP ratios, (using some acidic heated digestions to recover total C,N,P from particulate samples) and say something about what the nutrient limitations were for various algae in my system. My system runs a NO3 deficit - tests zero, and consumes whatever I add, so maybe that deficit might show up in algae cells from my system??....

(these first two chart are C/P and N/P, so put them together and you have the mole C/N/P ratios of these various samples)

This 3rd chart for completeness is the other ratio, CN - sometimes this is used as indicator for the carbs to protein in an algae.

What are these samples?
light green is a green cyanobacteria mat, (one sample I incubated with a PO4 additive to see if the cell ratios responded in ~3days)
yellow is not from my system. it's a for-sure N-fixing heterocyst containing cyanobacteria (anabaena) from a bloom in a lake (with <=0.1ppm NO3) by my house.
red is a red oscillatoria-like cyano, I incubated samples with N and P additions to check for cell ratio responses.
Dark green is derbesia (GHA).
Gray is the silt that comes out of my sandbed if you shake it and let the sand settle and test the cloudiness that remains in the water.

Long story short: the raw amounts (as mass %CNP) that I measured lined up decently well with what I could find from published results, and none of the ratios even fell clearly into where researchers draw the line for the camps of N-limited or P-limited. (N-fixing Anabaena is the exception). Also the ratios in the silt tell me most of the P is abiotic, bound to aragonite, and not in living cells.

So my takeaway here is that even the ratios of the cells themselves tell you very little, because organisms have so many ways to adapt. But I learned that the various cyanos and GHA ratios look shockingly similar in my system, and maybe that's weak evidence against my cyano doing some N-fixing.

 

[Dan_P]

This Redfield ratio thing always pops up on here and every other forum. For some reason many people have been convinced that it has something to do with reef tanks, let alone actual reefs.

The Redfield ratio is about the consistent molar ratio between carbon, nitrogen and phosphate of the deep ocean and the biomass of phytoplankton. The original proposal was a C:N of 106:16:1. Further research has pushed this to 163:22:1.

Now remember this is molar ratio. Not a ratio of parts per million. And thus you can see that most posts about the Redfield are already mistaken.

So for example you'll read someone saying how they want there nitrate to be 16 ppm and phosphate 1 ppm to keep it in line with the Redfield ratio. Yet this is actually 25 uM nitrogen and 1 uM phosphorus. Or a ratio of 25:1. Also for some reason everyone chooses to ignore the carbon part of the ratio. Not sure why, but I'm guessing it revolves around the fact that adding 106 ppm of organic carbon would probably be bad. (In a 50 gallon tank this would be like adding ~48 grams or a little bit greater than3 tablespoons of sugar.)

Anyways it really doesn't matter because the relationship between the deep ocean and phytoplankton has no bearing on the reef or the reef tank. The way to best show this to ask the question what does the reef actually look like? Well glad you asked. For example a recent paper looking at the Great Barrier Reef measured the respective nutrient levels at

Dissolved organic carbon - 83 umol
Dissolved inorganic nitrogen (ammonium/a/nitrate)- 0.26 umol
Dissolved inorganic phosphorus - 0.08 umol

For a ratio of 1038 : 3.25 : 1 (You'll see similar numbers when you look at other reefs.)

So yeah clearly not the Redfield. Oh and this number is a snapshot, not going to go too much into specifics but a reef's nutrients are in massive flux. Reefs are not deserts, there is just massive competition to internalize any little speck of usable C:N

There are many, many more reasons the Redfield has nothing to do with anything we do but hopefully the above is pretty clear already.

So please please retire the Redfield

Let me know below if you have any other questions, comments.

I am trying to decide whether “stupid and pointless” is redundant

Keep up the thought provoking posts!

 

[Randy Holmes-Farley]

Here's a copy and paste of something I wrote in a different thread Friday:

I'd note that the Redfield ratio is of almost no use to a reefer, and folks widely misunderstand what it really is and what (if anything) to do with it.

Even within the narrow selection of "macroalgae", it does not usefully describe their contents. In a single study of macroalgae growing at a single ocean site, the values for N : P ratio ranges over a factor of more than 5:

Wayback Machine

 

[Dan_P]

Here's a copy and paste of something I wrote in a different thread Friday:

I'd note that the Redfield ratio is of almost no use to a reefer, and folks widely misunderstand what it really is and what (if anything) to do with it.

Even within the narrow selection of "macroalgae", it does not usefully describe their contents. In a single study of macroalgae growing at a single ocean site, the values for N : P ratio ranges over a factor of more than 5:

Wayback Machine

Can we then have the mention of “redfield” in a post automatically turned into a smiley face or a line of asterisks?

 

[tripdad]

Thank you to the OP for two points made. That the Redfield ratio has no real correlation to a glass box in my living room. Second, that reefs are NOT deserts but rather very high flux environments. Been preaching both for years with little to no confirming opinions. Thanks for the science to back it up. Nice post !

 

[flampton]

Fun thread. Let me drop this here for kicks. I got this idea that I could look at the cell CNP ratios, (using some acidic heated digestions to recover total C,N,P from particulate samples) and say something about what the nutrient limitations were for various algae in my system. My system runs a NO3 deficit - tests zero, and consumes whatever I add, so maybe that deficit might show up in algae cells from my system??....

(these first two chart are C/P and N/P, so put them together and you have the mole C/N/P ratios of these various samples)

This 3rd chart for completeness is the other ratio, CN - sometimes this is used as indicator for the carbs to protein in an algae.

What are these samples?
light green is a green cyanobacteria mat, (one sample I incubated with a PO4 additive to see if the cell ratios responded in ~3days)
yellow is not from my system. it's a for-sure N-fixing heterocyst containing cyanobacteria (anabaena) from a bloom in a lake (with <=0.1ppm NO3) by my house.
red is a red oscillatoria-like cyano, I incubated samples with N and P additions to check for cell ratio responses.
Dark green is derbesia (GHA).
Gray is the silt that comes out of my sandbed if you shake it and let the sand settle and test the cloudiness that remains in the water.

Long story short: the raw amounts (as mass %CNP) that I measured lined up decently well with what I could find from published results, and none of the ratios even fell clearly into where researchers draw the line for the camps of N-limited or P-limited. (N-fixing Anabaena is the exception). Also the ratios in the silt tell me most of the P is abiotic, bound to aragonite, and not in living cells.

So my takeaway here is that even the ratios of the cells themselves tell you very little, because organisms have so many ways to adapt. But I learned that the various cyanos and GHA ratios look shockingly similar in my system, and maybe that's weak evidence against my cyano doing some N-fixing.

Not surprised at these results. Variations will be found with an excess or a true limitation. Having no nitrate isn't really a nitrogen limitation. And if you truly had limited nitrogen you would not be thrilled with your dying tank.

As far as fixation, well it's an extremely expensive process. 16 ATP to break the triple bond. So if there's prevalent ammonium/a, amines, nitrates, like our aquariums it would make biological sense to limit fixation. However I think there is probably some fixation, just not anything significant.

I am trying to decide whether “stupid and pointless” is redundant

Keep up the thought provoking posts!

Oh it's definitely redundant

 

[Lasse]

Funny

The way to best show this to ask the question what does the reef actually look like? Well glad you asked. For example a recent paper looking at the Great Barrier Reef measured the respective nutrient levels at

Dissolved organic carbon - 83 umol
Dissolved inorganic nitrogen (ammonium/a/nitrate)- 0.26 umol
Dissolved inorganic phosphorus - 0.08 umol

For a ratio of 1038 : 3.25 : 1 (You'll see similar numbers when you look at other reefs.)

This is the ratio you have in the source - the sea - but it not means that this is the ratio you found in different organisms - there the Redfield ratio is the ratio found in planktonic algae in the open sea. In macros you normal will found another ratio - in fish a third and so on. But for organisms that take up inorganic nutrients from the water - the ratio N/P can be of interest.. IMO - inorganic C can never be limited in saltwater that have an alkalinity around 2,5 mekvl (7 dKH)

This article indicate that N/P ratio can have an importance in bleaching events - combined with thermal stress.

Limited phosphorus availability is the Achilles heel of tropical reef corals in a warming ocean - Scientific Reports

During the 20th century, seawater temperatures have significantly increased, leading to profound alterations in biogeochemical cycles and ecosystem processes. Elevated temperatures have also caused massive bleaching (symbiont/pigment loss) of autotrophic symbioses, such as in...

www.nature.com

Redfield ratio maybe be dead in reefing but - IMO - N/P ratio in the water can have an importance

Sincerely Lasse

 

[Garf]

I spent a lot of time 6 or 7 years ago researching the N/P ratios of algae to gain info on algae scrubber effectiveness. I could find no consistency. Temperature, light, flow, pH, nutrient availability, other algal presence all seemed to alter ratios, as I’m sure bacteria species present also does. I gave up.

 

[flampton]

I spent a lot of time 6 or 7 years ago researching the N/P ratios of algae to gain info on algae scrubber effectiveness. I could find no consistency. Temperature, light, flow, pH, nutrient availability, other algal presence all seemed to alter ratios, as I’m sure bacteria species present also does. I gave up.

This right here!

 

[flampton]

One thing I would like to add to make things a bit more 'complicated'.

When we test our aquarium water we get a 'global' readout. Same when scientists test parameters on the reef. The thing that these do not show you at all is the absolute flux of nutrients.

This flux (movement) of nutrients is an extremely important concept on the reef and in our aquariums.

The easiest example I can give is two aquaria exactly the same size with the exact same nitrate and phosphate levels. In one of them the aquarist feeds 10 cubes of food a day with a algae turf scrubber and skimmer. In the other the aquarists feeds 1 cube of food a day and uses just a sock.

Well obviously the one aquarium has 10x the amount of nitrogen and phosphate moving through it! And I will tell you the 10 cube willhave a more mature, healthy, growing system. (Yes there is a point of too much, 20 cubes might just be growing algae for algae growing sake)

__________________________________________________________________________________

Another thing that is not widely acknowledged is that there will also be nutritional concentration gradients. This means that some areas of your tank will have more and some areas will have lesser concentrations. In fact on the reef these concentration gradients are very important. Thus when we look at the overall reef and see these extremely low nutrient numbers it suggests a desert. However it has become clear that this is because all the nutrients are within organisms not out floating around. And one of the ways these nutrients flux through is through little tiny bacterial explosions. When a bacteria lyses it 'spills' its guts, so vitamins, amines, phosphate stores etc. Thus whatever is living next to the bacterial explosion will see a localized concentration increase. Now bacteria are small and this might not seem like anything important. Except...

Almost a half of the bacterial population turns over EVERY SINGLE DAY! And the bacterial population on the reef is around 1,000,000 cells/ml of water. Thus a cup of reef water would contain ~245,000,000 bacteria! And half of them die every 24 hours! (and the population rebounds every 24 hours). These nutrient explosions help move food up to multicellular organisms. So the original idea of bacteria feed single celled eukaryotes which feed multicellular eukaryotes etc. is not actually the whole story at all.

One of these days I'll look into how we can mimic this process in our tanks

 

[Lasse]

hen we test our aquarium water we get a 'global' readout. Same when scientists test parameters on the reef. The thing that these do not show you at all is the absolute flux of nutrients.

This flux (movement) of nutrients is an extremely important concept on the reef and in our aquariums.

That´s true - but in an aquarium you can at least for P see if your input or/and the leak from stones and sand is enough as a flux. If concentration of P is rising - input is to high and if it decrease - the input is to low. With N it is a little bit more complicated because there are more than 1 inorganic source of N.

But in the article I linked to - the authors indicate that thermal stress could cause a P deficiency if the ratio N/P was too high and hence starting a bleaching event

Sincerely Lasse

 

[flampton]

That´s true - but in an aquarium you can at least for P see if your input or/and the leak from stones and sand is enough as a flux. If concentration of P is rising - input is to high and if it decrease - the input is to low. With N it is a little bit more complicated because there are more than 1 inorganic source of N.

But in the article I linked to - the authors indicate that thermal stress could cause a P deficiency if the ratio N/P was too high and hence starting a bleaching event

Sincerely Lasse

This paper does not really point to a ideal ratio at all. In fact it argues the exact opposite of what you're suggesting. The paper is arguing that the ratio of N: P in seawater must change when the aquaria goes from 25C (77F) to 30C (86F) if you want to keep corals from bleaching.

Basically the ocean nutrient concentrations of <0.5um DIN, <0.01um DIP are just fine for corals until you cook them. Then to try and rescue them from this cooking you can increase the DIP to 0.2um and they won't bleach.

In essence you're looking at a stressor event and seeing what could be done. This is not what we strive for in aquaria. We necessarily want to reduce stressors.

Thus what is the ideal ratio when there is no heat stress? Well it would be pretty easy to argue the starting point should be that the global ratio and amounts should be as close to the reef as possible.

Yet we know that is a very dangerous place to be as an aquarist, on the cusp like that (these levels are very low e.g. my original example of the Great Barrier Reef this would be a nitrate of ~ 0.16ppm and phosphate of ~0.008 ppm.)

So we back off from the edge and necessarily run our aquariums under carbon limitation instead.

And since neither nitrogen or phosphate is limited there is going to be no important ratio between the two.

BTW NONE of this matters because like I mentioned before these global measures give you no idea what the actual nutrient flux is.

Imagine taking a picture of a car going 200mph with a really good camera. If the shutter is quick enough you will have no idea the car is even moving (though to be fair your brain will use background info to suggest velocity.) Same with the nutrients in your tank. Your brain uses your numbers COMBINED with how the tank looks to suggest they're at the right levels. That is why there is so many nutrient level fights on the forum, haha!!

 

[Lasse]

So we back off from the edge and necessarily run our aquariums under carbon limitation instead.

The nutrient in the water column is mostly interesting from photosynthetic organism point of view - ie autotrophic organisms. They use inorganic N and P. And of cause inorganic C. To talk about a carbon limitation in this aspect is not true. As I said before - saltwater with alkalinity around 2.5 mekv is in no way limited according to inorganic carbon. All phototrophic organisms in saltwater I´m aware off have the possibility to use (or convert) mainly HCO3 into needed CO3

If you look at heterotrophic organisms - its true - an aquarium is limited in organic carbon - especially of the form we use to call DOC (Dissolved Organic Carbon). But that has nothing to do with the inorganic balance of N,P and C for the phototropic organisms.

Before your fingers get overheated in attempt to tell me that I´m an idiot that do not understand that bacteria will - in especially in the presence of a "fast" organic carbon sources (DOC) - convert the organic carbon into inorganic carbon (namly CO2). I can tell you that I understand that - but I also understand that adding CO2 will not affected the storage level of inorganic carbon (the major part of the alkalinity) - it will only affect the pH and hence the equilibrium between CO2 <->H2CO3 <-> HCO2 <-> CO3 - not the total stored amount. I also understand that CO2 is a gas and will follow the equilibrium laws in an air/water interface and disappear from the element we call saltwater.

I have never talk about a ideal ratio of nutrients in the water - it will be different in different situations. If you run a macro dominated tank there the N/P ratio in the organisms often can exceed 50:1 and that your ratio in the water is around 20:1 even with your influx (the concentration in the water column is the difference between production/import and internal consumption) - you do need to be an Einstein to understand that the storage of N in the water column will be depleted in time and transferred into the macros in another ratio.

The ratio (read the left over or storage pool) of inorganic N and P need to be adjusted (IMO) to the phototropic organisms demand for these nutrients. And if you chose to have 0 nutrients in the water - your daily influx of these two inorganic nutrients must have a ratio that will not create an growth limitation of your phototrophic organisms.

I will - with the stubbornness of a fool - still say that according at least P - measurements of the left over or with other words - the storage pool in the water column - with help of PO4 measurements is important. If the concentration rise - internal production/equilibrium/import is higher than internal consumption/equilibrium/export - if it decline - If the concentration decline - internal production/equilibrium/import is lower than internal consumption/equilibrium/export, With inorganic N its more complicated - only measurement of NO3 can give a false impression of the inorganic N/P ratio but an indication if the storage pool of inorganic N. I use Triton N-DOC analyses in order to check my whole storage pool of inorganic and organic N (in the water column) but the NO3 concentration as a tool in order to get a snapshot now a when where the system is going.

Sincerely Lasse

 

[Garf]

The nutrient in the water column is mostly interesting from photosynthetic organism point of view - ie autotrophic organisms. They use inorganic N and P. And of cause inorganic C. To talk about a carbon limitation in this aspect is not true. As I said before - saltwater with alkalinity around 2.5 mekv is in no way limited according to inorganic carbon. All phototrophic organisms in saltwater I´m aware off have the possibility to use (or convert) mainly HCO3 into needed CO3

If you look at heterotrophic organisms - its true - an aquarium is limited in organic carbon - especially of the form we use to call DOC (Dissolved Organic Carbon). But that has nothing to do with the inorganic balance of N,P and C for the phototropic organisms.

Before your fingers get overheated in attempt to tell me that I´m an idiot that do not understand that bacteria will - in especially in the presence of a "fast" organic carbon sources (DOC) - convert the organic carbon into inorganic carbon (namly CO2). I can tell you that I understand that - but I also understand that adding CO2 will not affected the storage level of inorganic carbon (the major part of the alkalinity) - it will only affect the pH and hence the equilibrium between CO2 <->H2CO3 <-> HCO2 <-> CO3 - not the total stored amount. I also understand that CO2 is a gas and will follow the equilibrium laws in an air/water interface and disappear from the element we call saltwater.

I have never talk about a ideal ratio of nutrients in the water - it will be different in different situations. If you run a macro dominated tank there the N/P ratio in the organisms often can exceed 50:1 and that your ratio in the water is around 20:1 even with your influx (the concentration in the water column is the difference between production/import and internal consumption) - you do need to be an Einstein to understand that the storage of N in the water column will be depleted in time and transferred into the macros in another ratio.

The ratio (read the left over or storage pool) of inorganic N and P need to be adjusted (IMO) to the phototropic organisms demand for these nutrients. And if you chose to have 0 nutrients in the water - your daily influx of these two inorganic nutrients must have a ratio that will not create an growth limitation of your phototrophic organisms.

I will - with the stubbornness of a fool - still say that according at least P - measurements of the left over or with other words - the storage pool in the water column - with help of PO4 measurements is important. If the concentration rise - internal production/equilibrium/import is higher than internal consumption/equilibrium/export - if it decline - If the concentration decline - internal production/equilibrium/import is lower than internal consumption/equilibrium/export, With inorganic N its more complicated - only measurement of NO3 can give a false impression of the inorganic N ratio but an indication if the storage pool of inorganic N. I use Triton N-DOC analyses in order to check my whole storage pool of inorganic and organic N (in the water column) but the NO3 concentration as a tool in order to get a snapshot now a when where the system is going.

Sincerely Lasse

I also messed with adding CO2 to my algae scrubber many years ago. It doubled mass on its next cycle. It also harbored a slime bacterial colony downstream of the scrubber, presumably fueled by algae exudates. I assumed this was carbon limitation but I’m no scientist. I also asked on RC about the possibility that algae exudates could be used as a carbon dosing source and @Randy Holmes-Farley said “Algae can be quite leaky” or something along them lines, which I found quite funny.