Nitrate- cannot get it to fall

[BeanAnimal]

In supply and consumption certain nutrient ratios matter but not in water concentrations (standing stock of nutrients).

If we take the example of the Redfield ratio N:P 16:1 and you have for example a culture of plankton algae, it makes sense if the supply is also in the ratio 16:1 to create a steady state if you want to run a chemostat culture.

You may run a reef tank similar to a chemostat by creating a steady state of supply and consumption. Then the nutrient concentrations in your reef tank remain constant and, if you want, at low concentrations without getting limiting. Ratios of consumption in reef tanks will differ from the Redfield ratio.

Agreed. Matching supply to consumption prevents either nutrient from becoming limiting or accumulating to a harmful level. I think that somewhat goes to what @Lasse is driving at with regard to knowing that consumption"ratio" for a given system and desired state. He can then regulate his input or export to "chase" his balance by automation instead of manual correction.

 

[JonasRoman]

There are no "true" and "false" phosphates, just orthophosphate and so on, I have commented on this here already.

Po4 unbound in free in water is what photometry measure. Besides that we have P incorporated in organics and that is together with free po4 what icp oes P is measure. That mean icp oes wrongly assume all P is coming from free po4 meaning the calculated po4 from icp is always to various extent false high. Is this a problem? Yes, as sometimes the diff is 100%
I have showed that several times. Thats why more and more icp labs include a photmetric measure.
Take home message is you can't "calibrate" your home photometer with icp calculated.

 

[JonasRoman]

To that end, many people promoting “ratios” are using ppm instead of molar quantities, so the numbers they cite are not even the Redfield ratio or whatever other ratio they think they are promoting.

Ofcourse we (most of us at least) know its molar atoms. For the lazy guy you can take nitrate in ppm * 1.54 divide by po4 in ppm. That gives NP ratio in molar.

 

[Hans-Werner]

You now perfectly what I mean when I express in that way of pedagogical reason. Po4 unbound free in wayer is what photometry measure. Besides that we have P incorporated in organics and that is together with free po4 what icp oes P is measure. That mean icp oes wrongly assume all P is coming from free po4 meaning the calculated po4 from icp is always to various extent false high. Is this a problem? Yes,as sometimes the diff is 100% I have showed that several times.

Why is a higher total phosphate a problem? When I did photometer tests and digestion to get total phosphate I got sometimes 8 times higher total phosphate compared to orthophosphate.

I suspect that the problem is not the high total phosphate of ICP but the low orthophosphate of photometers. I also have stated this in the other thread. Coral can make use of total phosphate, not only of orthophosphate. Like many other organisms corals excrete alkaline phosphatase to make organic phosphates and polyphosphates available.

This is not pedagogical but the central question: Is total phosphate really less available to corals than orthophosphate? If not, "true" is give to the wrong parameter, the total phosphate should be "true" phosphate.

The fact that we have more experience with orthophosphate doesn't satisfy to declare it as "true".

 

[JonasRoman]

With phosphate this may be the case at low natural phosphate concentrations

What is the evidence for that ? Strictly its the zooxanthelle we are talking about. I do not think that dinoflagellates uptake of po4 stops when po4 reach 0.02. Still higher than on a natural reef. I am not sure its correct at all that nutrient uptake stops before it reaches zero for a specimen that is coming from natural conditions adapted to ultra low N and P situations. Where is your study that support this?

 

[JonasRoman]

photometer tests and digestion to get total phosphate I got sometimes 8 times higher total phosphate compared to orthophosphate.

If its a problem is up to user to decide. I just say its a false value you get from icp. We are not interested in total P including organics. We are only interested in free po4 in water=zooxanthelle food.

 

[JonasRoman]

suspect that the problem is not the high total phosphate of ICP but the low orthophosphate of photometers. I al

At least in my case this is not the ruth. My photometer measure ×- 0.005 and is always fine tuned versus Hach ref solution.

 

[JonasRoman]

This is not pedagogical but the central question: Is total phosphate really less available to corals than orthophosphate? If not, "true" is give to the wrong parameter, the total phosphate should be "true" phosphate.

Thats a completely different question as that gives totally new reference interval. So far we are talking about and understanding the free po4 as a zooxanthelle source.
It may be of interest to know total P aswell as ling as you understanding the difference. Most icp interpreter do not.

 

[JonasRoman]

phosphate is at the minimum uptake concentration at 0.2 µM/L

According to info when I search on his is that this is not correct. On the contrary I found some data that corals may thanks to active channels absorb down to almost zero independent of the intracellular concentration. A mechanism to manage the natural reef ultra low po4. So if this info is correct coral may absorb far lower than 0.02 ppm po4.

 

[Hans-Werner]

What is the evidence for that ? Strictly its the zooxanthelle we are talking about. I do not think that dinoflagellates uptake of po4 stops when po4 reach 0.02. Still higher than on a natural reef. I am not sure its correct at all that nutrient uptake stops before it reaches zero for a specimen that is coming from natural conditions adapted to ultra low N and P situations. Where is your study that support this?

See for example Sorokin, "Coral Reef Ecology", who did tracer experiments to measure uptake and release.

Zooxanthellae is just a part of the symbiont.

I just say its a false value you get from icp.

In no case it is "false", it is just another fraction or parameter. You can't compare and equate different fractions or parameters.

 

[JonasRoman]

no case it is "false", it is just another fraction or parameter. You can't compare and equate different fractions or parameters.

I think you know exactly what I mean. This turns to be a language issue. I have explained my best.

 

[JonasRoman]

See for example Sorokin, "Coral Reef Ecology", who did tracer experiments to measure uptake and release.

Its divergence in the info then. I found some good articles about the sodium-po4 channel making coral absorb po4 "if they need" far below your stated 0.02 ppm.

 

[Hans-Werner]

Its divergence in the info then. I found some good articles about the sodium-po4 channel making coral absorb po4 "if they need" far below your stated 0.02 ppm.

See also here and here. However I still highly recommend the Sorokin book, and I think the tracer method is very good and conclusive.

Michaelis-Menten kinetics and nutrient uptake is a central point in algal culture and ecological physiology of algae, since you asked for the zooxanthellae. I have read about all this 30 years ago and it is one of my main interests since then. I have prepared and given lectures for symposiums about nutrients.

 

[JonasRoman]

Welcome to the club where we have used a lot of last decades in try to learn and read about this fascinating field. I do not doubt your skills.

I hope you can understand that its natural to question the statement that a zooxanthelle can't absorb po4 when its below 0.02 especially thanks to active transports. The article I found was about how the zoo could absorb po4 in ultralow conditions as long as sodium existed as it was a sodium dependent channel.
Anyway. I will search for your links when time. Thanks for good links

 

[Hans-Werner]

Welcome to the club where we have used a lot of last decades in try to learn and read about this fascinating field. I do not doubt your skills.

I hope you can understand that its natural to question the statement that a zooxanthelle can't absorb po4 when its below 0.02 especially thanks to active transports. The article I found was about how the zoo could absorb po4 in ultralow conditions as long as sodium existed as it was a sodium dependent channel.
Anyway. I will search for your links when time. Thanks for good links

The zooxanthellae sit in the coral tissue. They are surrounded by coral tissue. Ions cannot penetrate cell membranes except through exchange systems.

 

[JonasRoman]

The zooxanthellae sit in the coral tissue. They are surrounded by coral tissue. Ions cannot penetrate cell membranes except through exchange systems.

Ofcourse. As I said, active transport with sodiumchannels to transport PO4. Not all substances need active transport though. CO2 for instance, it diffuse passively through cell membranes. But Ca need a Ca- ATPase to be trasnported (and at same time H ions is expelled). Also the HCO3 needs a trasnport protein to travel into the action site. We know quite much about this as human biologist, so its not so different when coming to cell wall.

 

[JonasRoman]

bump

 

[JonasRoman]

See also here and here. However I still highly recommend the Sorokin book, and I think the tracer method is very good and conclusive.

Michaelis-Menten kinetics and nutrient uptake is a central point in algal culture and ecological physiology of algae, since you asked for the zooxanthellae. I have read about all this 30 years ago and it is one of my main interests since then. I have prepared and given lectures for symposiums about nutrients.

So I have now red partial of the first link(discussion and summary)
Its interesting and have similar message as some other links posted here: Very Low Po4 is bad and If you add a Nitrogen excess to that its even worse for the symbiont membrane stability, so its a similar message.

Its also interesting that the coral increase the P uptake during thermal stress as a way of prevent bleaching. At same time they saw the opposite for N uptake, and debate if its a concequence of zooxanthelle reduction (beginning of bleaching) or deliberately by the coral to prevent bleaching? The first theory is more easy to adapt but the second more beatiful.

I couldnt find anything about that zoo cant assimilate Po4 if below 0.02, but on the contrary , it could increase and adapt the P utake during stress conditions to prevent bleaching. Right?

 

[Dan_P]

Good point.
Too me the difference between chasing a number and keeping things in check is where a numbers becomes a goal in stead of our animals thriving.

I’ve had my tanks (lots of SPS) thrive at nitrates anywhere between 0 and 100.

So, lets leave out the word chasing: in my opinion there is currently no evidence that any fixed nitrate number is universally best.

OK, thanks for the clarification.

 

[Lasse]

This thread has totally got off track like a train hitting the canyon bottom because the bridge was blown up So let me blow up the whole canyon. Its a lot of discussion of nutrients waste in the water column and the useless of both exact figures and N/P ratio with 100% concentration on the need of corals (Corals was not even with in the first post in this thread) IMO - we are all attacking the problem .through a one-sided perspective regarding how corals absorb nutrients and what is beneficial for them or not. However, the biosystem we call an aquarium contains more than just a single organism; we are not merely trying to get one type of organism to survive and grow.

Our systems consist of thousands of different organisms that both counteract and interact with one another.

This is where Delbeek’s observations become interesting—and partly align with my own experiences. There appears to be a range—expressed as a molar N/P ratio—within which the entire system functions well, resulting in healthy hard corals. Deviating from this ratio tends to lead to issues that compromise coral health or survival. The optimal range he discusses is quite broad: between 1:1 and 100:1. In my opinion, he focuses on the health of the entire biosystem, and that is the same perspective I take.

Personally, I have a lingering concern that a ratio that is too low is not ideal at the system level.

However, to obtain a comprehensive picture that accounts for the extremes, I believe organic carbon must also be included in the ratio. This is where it gets difficult, as we lack a simple method for measuring it.

For over three months now, I have been taking almost daily measurements of NO3 and PO4 in my aquarium. During the last month, I have also tracked the amount of food I add and the quantity of 100% ethanol I dose into the tank.

My problem is - what should I link my measurements to. How well my corals do, how well my fish do. how well my snails do and so on. The problem I see is all of these indicators is too slow. I need anothe indicator or biomarker. Probably have I found something that respond a little bit faster than other indicators.

I will comeback to this later on in my own thread.

Sincerely Lasse