Redfield Ratio Revisited – What are we doing wrong?

[Dan_P]

It is impossible - and you know it. It is like saying that Colombus should have taken an airplane around the world in order to find another way to India.

Not impossible but very, very difficult. The point is that if the question of species proliferation in an aquarium is not being answered scientifically, then all the conjectures, uncontrolled experiments and millions of pieces of anecdotal data in the world are not going to help develop an understanding of this problem. When a hypothesis is made that NO3 and PO4 have an effect and it cannot be consistently reproduced, then the hypothesis is questionable.

But let it us turn the question upside down. All system is different - every system is its own ecosystem with different microbial communities - in the US, in the UK in Brazil and in Sweden.

The “every aquarium is different” notion is an excuse to explain why a hypothesis or conjecture fails to work. As seeming deep insight, it is worthless. It is just as sound to say “every aquarist is different, but every aquarium system is basically the same”. Which has more explanatory power?

Despite this, we know that in at least 80 - 90% of cyanobacteria and dinoflagellar outbreaks have been reported at low or unbalanced concentrations of PO4 and different form of inorganic nitrogen.

”80-90% Have been reported“ by whom? where are these statistics being collected and verified? What definition of unbalanced are we talking about? Are we talking about aquaria only or in marine environments also? Were the organisms identified by microscopy in these outbreaks?

In addition, for cyanobacteria, the NO3 concentration seems to be critical. Low or no levels (and sometimes wrong ratio) of these substances in the water column have been shown to be the trigger over and over again.

And yet you say above it is impossible to conduct the experiment, of setting up six aquarium, develop the same bloom of cyanobacteria, diatom or dinoflagellate In each, and then treat three by adjusting the nitrate and phosphate and leave three untreated. When a phenomenon cannot be turned on and off, the understanding of it is incomplete, the root cause is unknown.

However - nearly all aquarium books refer to this problems as high nutrients problems - not because of evidences, scientifically investigations or thousand of of observations - but because of the fact that photosynthesizing organism in water needs nutrients in the water column - otherwise they will not grow. I´m with you when you say that these organisms have different ways of achieve the P and N they need - but for me it is very strong incidental evidence´s that low/zero or unbalanced ratios of these two nutrients is the trigger for creating different forms of monocultures existing of one or two species/genus that dominate the ecosystem. They can dominate because the environment that favour other competitors is gone and lost. They can dominate because they have other way of getting what they need - if the easy achieved sources not exist they can put in extra energy in order to survive and the domination and huge biomass will be the tool for further success if not the environment will change. Note - I´m not saying that the rise of nutrient in the water column (or changes of the ratios) will automatically defeat the monoculture but it is a tool to not get it back when the fight is over. Rising the nutrient during an outbreak of these organisms is not a quick fix - but lowering the nutrients (or change the ratio in the wrong way) is surly a quick fix in order to get an outbreak IMO.

OK, so we are back to it being possible to turn a bloom on by lowering the nutrients and then turning them off by raising the nutrients. Let’s test that idea with six aquaria. How do we set them up to get six separate blooms and how do we adjust the nutrient levels in three to end the bloom? We will do this in one country as part of variable contrtol. Also, we will need to repeat this for each diatoms, dinoflagellates and cyanobacteria.

I have not mentioned diatoms - but for me is rather obvious that a diatom bloom in our aquaria is not triggered of visible Si in the water column - the use of ICP testings worldwide have shown that the normal Si levels in out aquarium is over 100 µg/L - even in well function aquariums without diatom blooms. However - there is a lot of investigations showing that at least some diatoms are specialist in using very low concentrations of inorganic P in the water column and I see diatoms blooms in our aquarium as a sign of low availability of PO4 not as a sign of Si in the water column.

But today - it seems that we instead of knowledge and understanding of complicated processes need something easy to put the blame on - however - this is nothing new - let us - as usually - say it with a song (and @Paul B get his supermodel at the same time)

Sincerely Lasse

I am looking forwards to your ideas for an experiment.

Dan

 

[Dan_P]

Dan I do not believe researchers have intention to publish studies to convince us hobbiysts of anything. Nor do I believe that the absence of studies that do not meet out expectations should move us away from science...

Those files attached are some examples among other studies that showed evidence favouring one or another group of organisms.

This was observed in nature and in vitro, and they actually cultivated some cyanos like Oscillatoria to research the best conditions of growth for it.

For diatoms and dinos most studies put them together in terms of nutrients (but it is well known the role of silica to support the first group).

Thank you for sharing the references. I have read the cyanobacteria review before. I have also seen many similar microorganism nutrient studies. After reading these three references, I would like to explore other ways to answer the question “what are we doing wrong?”.

Ahlgren’s review illustrates the exquisite experimental variable control that is needed while studying one organism for a pattern in growth versus nutrient level to emerge. By contrast, an aquarium consists of thousands of interacting species in hundreds of micro-environments with little variable control and typically under casual observation. Imagine being confident in claiming to see a link between microorganism population size and a small change in nutrient level in aquarium. Here is another way of thinking about this idea: humans are very good at seeing patterns where they really don’t exist.

I have a feeling that we might not be thinking thoroughly enough about the differences between the scientific findings and the aquarium. Our thought process is biased, in particular selection biased. We look at these papers for ideas and perspectives that align with our thinking and what we think is happening in the aquarium and totally neglected the data that would invalidate the links. A good example is the information in Ahlgern’s review. We see ratios and how varying them affects microorganism growth and we think it might explain microorganism growth in our aquarium. What we neglect to notice is that the explanatory power of these observations do not work so well in complex systems like the ocean. The other very important bit of information that is neglected when entertaining thoughts involving ratios is the concentration of nutrients. This is extremely important to consider to understand the relevance of the scientific findings. Is the nutrient concentration in the experiment in the range of my aquarium and is the size of the variable response as large as the response I want to explain. Said differently, is the signal in the experiment as strong as the one I perceive. And back to my previous point, can I even detect a signal like the one in the experiment when no variables in the aquarium are controlled. As we ponder “what we are doing wrong” let’s keep in mind that we just might be mistaken about the relevance of nutrient ratios.

Dan

 

[Reef and Dive]

I would like to add an important observation on this topic. Some reefers have noticed and I tested myself:

For very immature reefs or reefs that keep undetectable nutrients longterm, nitrate dosing to get a “good” N : P ratio demands a special caution.

As dinoflagellates benefit greatly from the “good” ratios, they can be the exact microorganisms that start to grow and one problem will be solved causing a bigger one.

One strategy to avoid that is keeping enough green algae (ATS or refugium for example), or even dosing some “good” heterotrophic bacteria.

 

[Dkmoo]

where i personally think the RR is useful, is not in setting up target No3/Po4 levels because:
1) No3/Po4 is only measuring what's left in our tank, which is not a true picture of what we put in and what was absorbed
2) it does not test all N and P sources in our tank.

In this sense, i agree with others here who says trying to fix your NO3 to a certain Po4 level is not useful - ie, assume you put in 1600 N and 100P, and your corals absorp 1599N and 99P, your test kits will show 1 ppm No3 and 1PPM, applying the RR ratio in this case will mean you freaking out that your tank is out of balance when really it is not.

I think when people realize what is it that we are testing with our kits vs what RR is saying, is we reallize that it's not exactly apples to apples. Where i have personally applied this concept to troubleshoot my tanks is using it to point to a direction on where to go - combined with it's concept that different ranges tend to promote different organism. ie, when there is an imbalance, that has to mean what you put in is not matching what is absorbed. does that result in you having high levels of Po4 but near 0 lvls of No3? so you suddenly have cyano issues? have you been feeding mostly high P foods? is your fuge not growing? These different things help you correctly diagnose your problem and find solution - with RR as the unifying theory that explains all this - again, not really due to trying to fix that end residual product of no3/po4 to cerrtain level, but using it to understand what is or is not happening in your tank.

 

[Reef and Dive]

where i personally think the RR is useful, is not in setting up target No3/Po4 levels because:
1) No3/Po4 is only measuring what's left in our tank, which is not a true picture of what we put in and what was absorbed
2) it does not test all N and P sources in our tank.

In this sense, i agree with others here who says trying to fix your NO3 to a certain Po4 level is not useful - ie, assume you put in 1600 N and 100P, and your corals absorp 1599N and 99P, your test kits will show 1 ppm No3 and 1PPM, applying the RR ratio in this case will mean you freaking out that your tank is out of balance when really it is not.

I think when people realize what is it that we are testing with our kits vs what RR is saying, is we reallize that it's not exactly apples to apples. Where i have personally applied this concept to troubleshoot my tanks is using it to point to a direction on where to go - combined with it's concept that different ranges tend to promote different organism. ie, when there is an imbalance, that has to mean what you put in is not matching what is absorbed. does that result in you having high levels of Po4 but near 0 lvls of No3? so you suddenly have cyano issues? have you been feeding mostly high P foods? is your fuge not growing? These different things help you correctly diagnose your problem and find solution - with RR as the unifying theory that explains all this - again, not really due to trying to fix that end residual product of no3/po4 to cerrtain level, but using it to understand what is or is not happening in your

What matters more for this interpretation is actually available N and P.

The text on first page serves more as a possible structured interpretation, much more than a simple rule of numbers.

The same way when we have tons of algae with 0 phos and we already know the total tank phosphate is pretty high.

 

[Lasse]

A new article

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

Thanks @ksed for noticing me about this article

Sincerely Lasse

 

[flampton]

Yeah Redfield is meaningless as it pertains to the aquarium and the reef. I posted a thread on that recently- https://www.reef2reef.com/threads/r...-or-your-reef-is-stupid-and-pointless.810179/

Also the bane of science is incorrect assumption that correlation = causation. This is rampant through all threads on nutrient issues. The fact that some 'unwanted' organisms appear at certain levels of nutrients within a glass box does not mean the nutrient levels caused it. The way it is accepted on here is strange, because if you take that to it's logical conclusion you would expect there to be no reefs as the ocean would just be absolutely filled with Ostreopsis,

 

[Lasse]

The article indicate a relationship between N/P ratio, thermal stress and bleaching events.

It gives also some interesting indications according to NH3/NH4-N or NO3-N uptake ratios in different species - and how it change with temperature.

Sincerely Lasse

 

[Reef and Dive]

The article indicate a relationship between N/P ratio, thermal stress and bleaching events.

It gives also some interesting indications according to NH3/NH4-N or NO3-N uptake ratios in different species - and how it change with temperature.

Sincerely Lasse

Thanks Mr. Lasse!

Another great article to add to the list.

 

[Reef and Dive]

Yeah Redfield is meaningless as it pertains to the aquarium and the reef. I posted a thread on that recently- https://www.reef2reef.com/threads/r...-or-your-reef-is-stupid-and-pointless.810179/

Also the bane of science is incorrect assumption that correlation = causation. This is rampant through all threads on nutrient issues. The fact that some 'unwanted' organisms appear at certain levels of nutrients within a glass box does not mean the nutrient levels caused it. The way it is accepted on here is strange, because if you take that to it's logical conclusion you would expect there to be no reefs as the ocean would just be absolutely filled with Ostreopsis,

Did you take the time to carefully read the first page of this post?

Even better, have you checked the referenced articles, many I have appended during the discussion...

 

[flampton]

Did you take the time to carefully read the first page of this post?

Even better, have you checked the referenced articles, many I have appended during the discussion...

Yes I've read it, your conclusions are flawed. You cannot extrapolate ideal ratios from nitrogen or phosphate limited systems. Our reefs are (necessarily) carbon limited. And for sure I've yet to see someone run a tank (that doesn't incorporate free flow with the ocean) truly nitrogen/phosphate limited without crashing.

The ability of organisms to replicate isn't going to be ratio dependent, but dependent on overall levels. For the conditions is there enough nitrogen or phosphate? That's it. This is because free living organisms necessarily need to be flexible or they will not survive. (Which is actually great for us, since none of the organisms we want to grow would ever see the nitrate and phosphate levels of a home aquarium)

Second the observed global ratios of nitrogen and phosphate don't recognize the actual important factor, which is the flux of nutrients through the system. This static ratio also ignores that organisms within the tank are accessing DOM and POM first.

Also your explanation of carbon dosing is off. It's important to understand nitrate is a poor nitrogen source. The majority of the carbon dosing effect is from amines/ammonia being utilized before they have a chance to enter the nitrogen cycle.

Also you cannot extrapolate an organisms N: P ratio with how it utilizes these substrates. The amount of carbon availability will dictate the usefulness. If a bacteria is carbon limited they will waste nitrogen and phosphate. It will chew amino acids up and spit ammonia out. It will secrete phospholipases to access the fatty acid carbon, but will have no need for the phosphates. This is what is happening in our tanks. Most everything is wasted just to get to that organic carbon. And the phototrophs who aren't carbon limited 12 hours a day enjoy life. In essence our aquariums are eutrophic. If you want to see just add a bunch of carbon and watch the bloom

 

[Lasse]

Also you cannot extrapolate an organisms N: P ratio with how it utilizes these substrates. The amount of carbon availability will dictate the usefulness. If a bacteria is carbon limited they will waste nitrogen and phosphate.

As I say before - phototrophic organisms in saltwater are not and can´t be carbon limited. They live in an environment with lot of inorganic carbon - most of the alkalinity of around 2.5 mekv (7 dKH) is in one of the forms CO2 in the air <-> Air/Water interface <-> inorganic carbon in water <-> CO2<->H2CO3 <.> HCO3 <-> CO3 and it is an equilibrium system that means that if one of them get consumed there will be more of it coming from the others. The only thing we are talking about according to inorganic C/N/P ratio in the water column is for nutrient to organisms that in one or another way use photosynthesis in order to grow and survive. And once again carbon can´t be limited in this regard in saltwater with normal alkalinity.

Sincerely Lasse

 

[Randy Holmes-Farley]

The article indicate a relationship between N/P ratio, thermal stress and bleaching events.

It gives also some interesting indications according to NH3/NH4-N or NO3-N uptake ratios in different species - and how it change with temperature.

Sincerely Lasse

Since there are multiple threads running, I'll copy my comment from the other one for folks only reading this one:

Hi Lasse,

Can you explain how that article says the N : P ratio is important, rather than each of N and P is needed in an optimal range, and that optimal range might change with changing conditions such as temperature increases?

For the ratio to be the important, it would suggest that critical value is the ratio, rather than the absolute values, and that changing the absolute values with the same ratio is not important. I did not see that in the paper.

 

[Randy Holmes-Farley]

Thanks Mr. Lasse!

Another great article to add to the list.

Do you think it says the N : P ratio in the water is the critical factor? I don't see it.

Did they test different absolute values with the same ratio and find growth was the same? No.

All I see is that it says the optimal amounts of N and P may change as environmental conditions change.

That's hardly surprising, IMO.

 

[flampton]

As I say before - phototrophic organisms in saltwater are not and can´t be carbon limited. They live in an environment with lot of inorganic carbon - most of the alkalinity of around 2.5 mekv (7 dKH) is in one of the forms CO2 in the air <-> Air/Water interface <-> inorganic carbon in water <-> CO2<->H2CO3 <.> HCO3 <-> CO3 and it is an equilibrium system that means that if one of them get consumed there will be more of it coming from the others. The only thing we are talking about according to inorganic C/N/P ratio in the water column is for nutrient to organisms that in one or another way use photosynthesis in order to grow and survive. And once again carbon can´t be limited in this regard in saltwater with normal alkalinity.

Sincerely Lasse

Again copy paste from the other thread.

-------
In actuality you still are running a carbon limitation. To access the CO2 the phototrophs require light. The aquarist controls this by manipulating intensity spectrum duration. As well as those who run ATS or algal refugium control the production of organic carbon in a separate compartment.

 

[Reef and Dive]

Since there are multiple threads running, I'll copy my comment from the other one for folks only reading this one:

Hi Lasse,

Can you explain how that article says the N : P ratio is important, rather than each of N and P is needed in an optimal range, and that optimal range might change with changing conditions such as temperature increases?

For the ratio to be the important, it would suggest that critical value is the ratio, rather than the absolute values, and that changing the absolute values with the same ratio is not important. I did not see that in the paper.

The hole point of this review of articles was exactly NOT TO point to an optimal range, but actually to recognize tendencies based on availability.

This happens repeatedly, in vitro, in nature, in lagoons, AND in tanks.

I suppose most won´t deny that carbon dosing till nitrates lowers to near zero just stimulates cyano blooms - that´s just so frequent! And so explainable!

Do you think it says the N : P ratio in the water is the critical factor? I don't see it.

Did they test different absolute values with the same ratio and find growth was the same? No.

All I see is that it says the optimal amounts of N and P may change as environmental conditions change.

That's hardly surprising, IMO.

Not in the latest article. But in many others that I´ve researched the answer is YES. For ALL three.

They´re previously quoted.

Since there are multiple threads running, I'll copy my comment from the other one for folks only reading this one:

Please, if you have the time, check the first post.

It is a long thread with a research that took me months to gather and put together. I carefully read ALL articles referenced and can provide any of them for anyone that requires that...

Yes I've read it, your conclusions are flawed. You cannot extrapolate ideal ratios from nitrogen or phosphate limited systems. Our reefs are (necessarily) carbon limited. And for sure I've yet to see someone run a tank (that doesn't incorporate free flow with the ocean) truly nitrogen/phosphate limited without crashing.

Many of the "in tank studies" provided were done in limited systems.

They were actually proposed to explain the noted changes in the wild.

Yes I've read it, your conclusions are flawed.

Could you be more specific about that? That was a pretty long text...

What conclusions? And flawed for what reasons???

 

[Randy Holmes-Farley]

Not in the latest article. But in many others that I´ve researched the answer is YES. For ALL three.

They´re previously quoted.

Many??? Can you repost an article that shows that?

I truly have never seen an article that showed that an organism grows as a function of the N : P ratio rather than the absolute values of the nutrients. I don't even recall seeing a paper try to test that by taking a fixed N : P and looking at different absolute levels and the effect it has on growth.

nearly all papers I have seen find that N or P is a standard limiting growth factor, and adding more of that factor increases growth unless and until something else becomes limiting.

 

[N.Sreefer]

After skimming through this thread I got a layman question if cyano is observed should carbon dosing be stopped?

 

[Randy Holmes-Farley]

After skimming through this thread I got a layman question if cyano is observed should carbon dosing be stopped?

IMO, it is unrelated to the Redfield ratio, but cyano can take up organic carbon, and if the cyanobacteria is at problem levels, might be a reason to switch to a different carbon source, or stop entirely, yes. It was why I stopped vodka and chose vinegar instead.

 

[Reef and Dive]

Many??? Can you repost an article that shows that?

I truly have never seen an article that showed that an organism grows as a function of the N : P ratio rather than the absolute values of the nutrients. I don't even recall seeing a paper try to test that by taking a fixed N : P and looking at different absolute levels and the effect it has on growth.

nearly all papers I have seen find that N or P is a standard limiting growth factor, and adding more of that factor increases growth unless and until something else becomes limiting.

Attached. I have many more I can add (at work now). These are very nice articles worth reading.