Phosphorus starvation and nitrogen?

[Belgian Anthias]

The N: P ratio is of great importance in a reef aquarium. Phosphorus starvation has been identified as the leading cause of coral bleaching and is caused by the high availability of nitrogen and a shortage of phosphorus supply during periods of increased growth. (elevated temperature?). Personally, I assume that this applies to all essential building materials and not just phosphorus, but that is till now just an assumption I want to take into account.
As a skimmer constantly removes building materials but leaves most of the nitrogen untouched, a nitrogen surplus will inevitably arise in a daily fed aquarium, natural assimilation (growth) will not be able to restore this imbalance.
I assume, forcing fast growth as is the case with the addition of all kinds of preparations, such as to promote nitrate and phosphate uptake (dosing of organic carbons), can therefore, in certain circumstances, have nasty consequences if the availability of nitrogen is too high in proportion to the presence of other essential nutrients.
A too high nitrogen balance can only be restored by effectively removing only nitrogen and / or adding essential building materials. Finally, the constant use of the skimmer can be questioned in such circumstances.

Determining the N ratio in the water column is not that difficult but, how determining the N: other essential nutrients ratio?
What is known about the phosphorus removal of a skimmer? May I consider it to be in balance with the removal of other essential nutrients?
May nitrogen be the limiting factor for coral growth? Or must all essential nutrients unlimited be available at all times?

 

[Randy Holmes-Farley Verified Community Expert]

The N: P ratio is of great importance in a reef aquarium. Phosphorus starvation has been identified as the leading cause of coral bleaching and is caused by the high availability of nitrogen and a shortage of phosphorus supply during periods of increased growth. (elevated temperature?). Personally, I assume that this applies to all essential building materials and not just phosphorus, but that is till now just an assumption I want to take into account.
As a skimmer constantly removes building materials but leaves most of the nitrogen untouched, a nitrogen surplus will inevitably arise in a daily fed aquarium, natural assimilation (growth) will not be able to restore this imbalance.

I don’t know what you mean by remove building materials. Skimmers remove many things, including many organic forms of nitrogen.

I do not think that excess nitrogen is any more likely than excess phosphate since denitrification removes nitrate and not phosphate.

 

[Belgian Anthias]

I don’t know what you mean by remove building materials. Skimmers remove many things, including many organic forms of nitrogen.

I do not think that excess nitrogen is any more likely than excess phosphate since denitrification removes nitrate and not phosphate.

Reminerelized organics are the building materials for new growth. What is removed by a skimmer can not be re-used for natural nitrogen assimilation.

 

[Belgian Anthias]

The purpose of a skimmer is preventing complete remineralization as much as possible. The more efficient a skimmer removes organic forms the more denitrification must take place to prevent a nitrogen imbalance. In most reef aquaria the nitrification and or denitrification rate can not be managed as desired. A high nitrate-nitrogen level I do not consider to be a problem, only when insufficient phosphorus is available it may influence coral growth in a way it may harm the corals.
The passive denitrification rate often seems to be insufficient as a lot of reefers battle nitrate levels by promoting the assimilation of nitrogen and phosphorus, which needs all essential building materials must be sufficiently present to be effective and which does not change a thing to the nitrogen unbalance created by a skimmer, this way increasing the risk for coral bleaching if only the nitrate level is used as a guideline for dosing products with the purpose to take up nitrogen and phosphorus, as often advised on fora.

Also, the use of an algae scrubber will not restore the nitrogen balance.

It would be interesting to know if a skimmer removes relatively more or less nitrogen than phosphorus.
If phosphorus is actively removed using a phosphorus absorber, the removal rate should be manageable.

 

[Randy Holmes-Farley Verified Community Expert]

There are many processes unbalanced with respect to N and P. That is why I like to use many different types of nutrient export, to allow balancing them out to leave desirable levels of nitrate and phosphate.

 

[Dan_P]

The N: P ratio is of great importance in a reef aquarium. Phosphorus starvation has been identified as the leading cause of coral bleaching and is caused by the high availability of nitrogen and a shortage of phosphorus supply during periods of increased growth. (elevated temperature?). Personally, I assume that this applies to all essential building materials and not just phosphorus, but that is till now just an assumption I want to take into account.
As a skimmer constantly removes building materials but leaves most of the nitrogen untouched, a nitrogen surplus will inevitably arise in a daily fed aquarium, natural assimilation (growth) will not be able to restore this imbalance.
I assume, forcing fast growth as is the case with the addition of all kinds of preparations, such as to promote nitrate and phosphate uptake (dosing of organic carbons), can therefore, in certain circumstances, have nasty consequences if the availability of nitrogen is too high in proportion to the presence of other essential nutrients.
A too high nitrogen balance can only be restored by effectively removing only nitrogen and / or adding essential building materials. Finally, the constant use of the skimmer can be questioned in such circumstances.

Determining the N ratio in the water column is not that difficult but, how determining the N: other essential nutrients ratio?
What is known about the phosphorus removal of a skimmer? May I consider it to be in balance with the removal of other essential nutrients?
May nitrogen be the limiting factor for coral growth? Or must all essential nutrients unlimited be available at all times?

What N : P ratio are you referring to?

 

[taricha]

I'm not aware of data showing that N - P ratio in skimming could lead to high N vs P.
My tank constantly hits low to undetectable nitrate and occasionally higher P than I'd like.
I don't know which export mechanism is most responsible for the state of affairs: skimmer, chaeto, or denitrification.
Since macro algae can have variable uptake ratios depending on what nutrients are available, I consider it to be a factor that mitigates imbalance.
(While I agree with the premise of high nitrate, low phosphate being a problem, I think the OP first two sentences overstate the case.)

 

[rmurken]

My tank constantly hits low to undetectable nitrate and occasionally higher P than I'd like.
I don't know which export mechanism is most responsible for the state of affairs: skimmer, chaeto, or denitrification.

I’m going through this now. I dosed some NO3, and PO4 now coming down, seemingly as a result...although who knows.

Agree with your post generally.

 

[rmurken]

I don't know which export mechanism is most responsible for the state of affairs: skimmer, chaeto, or denitrification.

Also, I will say in my lightly-stocked tank, denitrification was enough to keep NO3 all the way down. I added chaeto for PO4. Realizing I may need to throw a bit of extra NO3 in to make it work.

 

[taricha]

Also, I will say in my lightly-stocked tank, denitrification was enough to keep NO3 all the way down. I added chaeto for PO4. Realizing I may need to throw a bit of extra NO3 in to make it work.

When everything is going my tank needs ~2ppm NO3 per day dosed to keep it above undetectable. And PO4 stays ~0.10ppm. So either my very typical foods (flake and frozen cubes) are unbalanced high P, or maybe I have magical super denitrifying bacteria.

 

[Dan_P]

I’m going through this now. I dosed some NO3, and PO4 now coming down, seemingly as a result...although who knows.

Agree with your post generally.

@taricha and I have been culturing cyanobacteria and other marine microorganisms this past year. One of the observations we made that surprised me was how a small patch of cyanobacteria or algae can quickly deplete nitrate and phosphate from the medium. As a result, I am no longer surprised to hear from aquarists with actively growing Chaeto that nitrate and phosphate levels are difficult to maintain. A healthy population of denitrifying bacteria will also keep nitrate levels low unless the system is overstocked.

The other observation we made or rather did not make was around nutrient ratios. What we actually tended to see is something that Randy mentioned. If their is adequate nitrate and phosphate for rapid growth of algae and cyanobacteria, the ratio is irrelevant. When you starve a system of nitrate and phosphate, the ratio does not matter, the organism suffers. We did no work on coral, but I suspect that they follow similar “laws”. Providing adequate nutrient levels enables optimum growth regardless of the ratio. The notion of stoichiometric ratios is a very useful notion in ecological studies but it seems likely that it is misunderstood and misapplied to aquarium care.

 

[Randy Holmes-Farley Verified Community Expert]

I’m going through this now. I dosed some NO3, and PO4 now coming down, seemingly as a result...although who knows.

Agree with your post generally.

That is certainly the expected, and often observed, result for a tank with N low enough to limit organism growth.

 

[taricha]

The other observation we made or rather did not make was around nutrient ratios. What we actually tended to see is something that Randy mentioned. If there is adequate nitrate and phosphate for rapid growth of algae and cyanobacteria, the ratio is irrelevant.

Agreed. The "ratio" I would care about in a tank is the ratio of the level of P or N to the daily consumption of the nutrient. For instance, I like to target 3 days worth of NO3.

 

[Belgian Anthias]

In natural nutrient-poor waters, corals mainly use organic nutrients provided and managed by the holobiont of which the symbionts are a very important member.
In oligotrophic waters, growth will be driven by a very low but constant supply of inorganic nutrients.
In the coral holobiont, the symbionts ( energy, carbon) , cyano's ( nitrogen), the measured (?) release of mucus ( rich in organic carbon and phosphorus) by the coral, managing the growth rates, will help to sustain the diversity needed to maintain the microbial community and for to make good use of what is provided. This seems only possible in waters with a by nature limited availability of organic carbon.
The conditions and nutrient availability in such a microbial community will be completely different from what is measured in the surrounding water.

During not normal increased growth, the supply may be insufficient to support the increased growth rate. The symbionts may grow to the dead (as a plant may grow dead when its roots are not able to supply the demand )

Although the N/P ratio matters, I do not think the N/P ratio in the water matters much for healthy coral growth, as long it is supplied. Of course, the supply will influence the growth rate.



How can a natural situation be translated into or compared with the situation in captivity?
The practice has proven corals may do very well in captivity and may adapt to a variety of captive conditions.
But often it goes wrong? Sometimes after a period of time, it suddenly happens. Why?

Reefers still struggle with translating a situation which was measured on a reef in the 90'ies, a situation by which increased nitrogen and phosphorus presence was measured on a reef.

What is measured is the result after it happened or during it is happening and is the result of the moment, and does not necessarily represent the situation of what caused it to happen.

What is measured in the water may not represent the ratio's present in a microbial community, where most of the work is done.

A low nutrient level may be maintained by a high growth rate. If that growth is interrupted the increasing N and P often will be blamed.

The method used to battle N may mess up the coral holobiont a lot more as a high N and or P level has been proven.

I am more concerned about the C/N ratio!

 

[King Turkey]

its all about stability. you can look into ratios all day. the one that matters is what nature provides (the ocean). I see better coral health growth and color from stability then chasing numbers and having a swing. I think if you have issues with numbers dropping or raising is not some magical fairy screwing it up its the owner. if things drop to fast then the biological balance of input to export is off balance same goes for going up. the key is to know what the cause is and to take action to have not only balance but most importantly stability.

 

[Dan_P]

In natural nutrient-poor waters, corals mainly use organic nutrients provided and managed by the holobiont of which the symbionts are a very important member.
In oligotrophic waters, growth will be driven by a very low but constant supply of inorganic nutrients.
In the coral holobiont, the symbionts ( energy, carbon) , cyano's ( nitrogen), the measured (?) release of mucus ( rich in organic carbon and phosphorus) by the coral, managing the growth rates, will help to sustain the diversity needed to maintain the microbial community and for to make good use of what is provided. This seems only possible in waters with a by nature limited availability of organic carbon.
The conditions and nutrient availability in such a microbial community will be completely different from what is measured in the surrounding water.

During not normal increased growth, the supply may be insufficient to support the increased growth rate. The symbionts may grow to the dead (as a plant may grow dead when its roots are not able to supply the demand )

Although the N/P ratio matters, I do not think the N/P ratio in the water matters much for healthy coral growth, as long it is supplied. Of course, the supply will influence the growth rate.



How can a natural situation be translated into or compared with the situation in captivity?
The practice has proven corals may do very well in captivity and may adapt to a variety of captive conditions.
But often it goes wrong? Sometimes after a period of time, it suddenly happens. Why?

Reefers still struggle with translating a situation which was measured on a reef in the 90'ies, a situation by which increased nitrogen and phosphorus presence was measured on a reef.

What is measured is the result after it happened or during it is happening and is the result of the moment, and does not necessarily represent the situation of what caused it to happen.

What is measured in the water may not represent the ratio's present in a microbial community, where most of the work is done.

A low nutrient level may be maintained by a high growth rate. If that growth is interrupted the increasing N and P often will be blamed.

The method used to battle N may mess up the coral holobiont a lot more as a high N and or P level has been proven.

I am more concerned about the C/N ratio!

What C/N are you referring to? How would we measure it? And what studies inform us about the importance of such a ratio? What is the value of this important ratio? And again, why would a ratio matter if there is sufficient amounts of both elements for optimum growth?

 

[rmurken]

My 2 cents...Unless you use NSW (and even then), the overall chemical composition and relative concentrations of various ions in a reef tank may be grossly similar to nature, but in the end it’s an artificial environment where you only manage the parameters that matter to the organisms. For instance, that’s the basic premise of synthetic salt mixes: “what are the needs of whatever lives in the resultant water?“ Not “this stuff mixes up to the exact composition of the ocean.”

So I don’t get the ratio concept here. Excess amounts of NO3 or PO4 aren’t a problem until they cause one. And it seems like people have broadly different experiences with respect to what works and what causes problems. Which suggests to me that the issue evades reduction to simple ratios.

 

[Belgian Anthias]

Salt mixtures are often compared with natural seawater parameters in comparative tests. In nature, NSW will supply what is needed, what is used will be replaced.
In a closed system, NSW will not be able to support the growth needed to install a proper carrying capacity without adding a food source.

Growing organisms will take up nutrients, for growth and respiration. They do not care about the N/P ratio in the water, even when N and P are present at a very low level, as long there is supply. Internally they will build up the C/N ratio needed, grow and multiply when ready. It may take more time to grow if the N/P ratio present is 1/1 compared to 16/1. On average Phyto contains 15.5/1, Zoo 16.5/1, benthic algae 30/1. Some symbionts (zoöxanhtellen) 52/1. It is said one may control benthic algae by maintaining the Redfield ratio for N: P due to the difference in N: P ratio. But is it not true that every organism can extract as much of the total building materials present as it needs and that only the effectiveness with which the organism can do this is important. It would also mean that either a very low nitrate content should be maintained or a high phosphate content since the weight ratio is about 10 nitrate: 1 phosphate. ref: CMF De Haes http://www.baharini.eu/baharini/doku.php?id=nl:makazi:chemie:redfield

I think, in nature, a 3/1 or 30/1 situation in the water is not a problem as the supply is theoretically limitless. The holobiont may be able to provide a food source having the ideal N/P ratio and everything else needed.
Problems may arise when for some reason the community is not able to provide what is needed, for example during a period of abnormal high growth, by losing essential members of the community, by viruses and or other pathogens.

In a closed aquarium system, It is very unlikely the presence of nitrate and or phosphate may become a real problem. If any doubts, both are managed easily.
But is it wrong to think that if enough is present in the water this may not be the case where the action is?

Must nitrate be added if not measurable?
I have never been in such a situation, I do not have any practical experience with LNS and VLNS.

Nitrate is an end product of the aerobic remineralization process as is CO2 and phosphate. It means nitrate will become available which is not the end product of the production of building materials needed for new growth. Nitrate is also the end product from maintaining an autotrophic carrying capacity, the removal of ammonia.
A safely stored nitrogen source becomes available without effecting alk, without closing the carbon cycle, without producing phosphate.
The intention of adding nitrate is to provide a nitrogen source to be used. It may be used for growth or by anaerobic respiration, supporting an anaerobic remineralization process, producing N2, CO2, and phosphate.

How the addition of not by the system produced nitrate will influence the natural remineralization processes and growth in a closed system in which a skimmer removes some organics constantly but very selective?
What may be the effect on the N/P ratio in the system?

What is measured is what is leftover at that moment.

 

[Dan_P]

Salt mixtures are often compared with natural seawater parameters in comparative tests. In nature, NSW will supply what is needed, what is used will be replaced.
In a closed system, NSW will not be able to support the growth needed to install a proper carrying capacity without adding a food source.

Growing organisms will take up nutrients, for growth and respiration. They do not care about the N/P ratio in the water, even when N and P are present at a very low level, as long there is supply. Internally they will build up the C/N ratio needed, grow and multiply when ready. It may take more time to grow if the N/P ratio present is 1/1 compared to 16/1. On average Phyto contains 15.5/1, Zoo 16.5/1, benthic algae 30/1. Some symbionts (zoöxanhtellen) 52/1. It is said one may control benthic algae by maintaining the Redfield ratio for N: P due to the difference in N: P ratio. But is it not true that every organism can extract as much of the total building materials present as it needs and that only the effectiveness with which the organism can do this is important. It would also mean that either a very low nitrate content should be maintained or a high phosphate content since the weight ratio is about 10 nitrate: 1 phosphate. ref: CMF De Haes http://www.baharini.eu/baharini/doku.php?id=nl:makazi:chemie:redfield

I think, in nature, a 3/1 or 30/1 situation in the water is not a problem as the supply is theoretically limitless. The holobiont may be able to provide a food source having the ideal N/P ratio and everything else needed.
Problems may arise when for some reason the community is not able to provide what is needed, for example during a period of abnormal high growth, by losing essential members of the community, by viruses and or other pathogens.

In a closed aquarium system, It is very unlikely the presence of nitrate and or phosphate may become a real problem. If any doubts, both are managed easily.
But is it wrong to think that if enough is present in the water this may not be the case where the action is?

Must nitrate be added if not measurable?
I have never been in such a situation, I do not have any practical experience with LNS and VLNS.

Nitrate is an end product of the aerobic remineralization process as is CO2 and phosphate. It means nitrate will become available which is not the end product of the production of building materials needed for new growth. Nitrate is also the end product from maintaining an autotrophic carrying capacity, the removal of ammonia.
A safely stored nitrogen source becomes available without effecting alk, without closing the carbon cycle, without producing phosphate.
The intention of adding nitrate is to provide a nitrogen source to be used. It may be used for growth or by anaerobic respiration, supporting an anaerobic remineralization process, producing N2, CO2, and phosphate.

How the addition of not by the system produced nitrate will influence the natural remineralization processes and growth in a closed system in which a skimmer removes some organics constantly but very selective?
What may be the effect on the N/P ratio in the system?

What is measured is what is leftover at that moment.

I think you make a wonderful case for why nutrient ratios provide us with no useful improvement to the way we maintain a reef aquarium. And I will go one step further and say that your expose on the complexity of nutrient uptake shows how complicated an ecosystem is, and that we have little hope in defining an ideal level of any nutrient. This all comes down to striving to achieve nutrient levels which are considered optimum and being guided by the appearance of the aquarium and its organisms to fine tune our procedures and dosing.

 

[EMeyer]

I'm not aware of data showing that N - P ratio in skimming could lead to high N vs P.
My tank constantly hits low to undetectable nitrate and occasionally higher P than I'd like.
I don't know which export mechanism is most responsible for the state of affairs: skimmer, chaeto, or denitrification.
Since macro algae can have variable uptake ratios depending on what nutrients are available, I consider it to be a factor that mitigates imbalance.
(While I agree with the premise of high nitrate, low phosphate being a problem, I think the OP first two sentences overstate the case.)

This has certainly been my experience; I've never seen high nitrates with low phosphates, only the opposite.