Redfield ratio

[brad]

Before debating how useful this calculation is, I wanted to have you check I am doing the calculation correctly.

If I have 120 gallons of salt water and a gallon of saltwater weighs 8.556 lbs, I have 465,712 grams of water. If the water has 100ppm nitrate, then I have 46.6 grams nitrate. Nitrate is 14/62 Nitrogen by weight, so I have 10.5 grams of nitrogen. If I have 0 grams of useable carbon, and want the redfield ratio is C:N = 106:16, I need to add 70.0 grams carbon. Sucrose is 144 / 342 carbon, so I need to add 165.5 grams of table sugar.

Why do I think this might be useful? So I can hurry up and dump exactly 165.5 grams of table sugar into my reef? No, my nitrates are not 100ppm, my volume is not exactly 120 gallons, and I am not insane. This gives me a testable hypothesis to calculate exactly how much sugar I need to add. Then I can figure out what constant rate to add it, and periodically test my water and see how fast nitrate goes down over that period of time. If my nitrates hit 0 long before the sugar is gone or are too high to be accounted for my input at the end of the period, I will know this calculation is useless. As long as nitrates follow what I expect, then I should be able to calculate how to lower nitrate by water changes and dosing a certain amount of sugar over a certain period of time.

 

[Randy Holmes-Farley]

Not a good way to go. The carbon in plankton will not correspond to what they eat, just like it doesn't in your body. They release a lot of it as CO2.

 

[Boomer]

As Randy pointed out not a good way. This RR has popped up now and then and is often misused and not understood. It is for Phytoplankton and Phytoplankton only. It will be different for x, y or z coral, x, y or z Algae, Zooplankton etc..

On that note you also left out P. If you throw in Diatoms then you have to add Si also.

RR = 106:16:1.

And it is a general avg and not a specific number for Plankton

 

[torhav]

I think you might be wrong about RR only effecting phytoplancton Boomer. I have read some research reports concluding effects on cyano as well. Tests done near sewage plants showed that removal of nitrates and not phosphates from the water entering the sea caused large cyano blooms. This was caused by wrong ratio between nitrate/phosphate.
I have also read that cyano is not capable of reproducing if the ratio is right (high nitrates).
I know this is the case in freshwater as I used to control algae, including cyano, with RR.
As cyano is the only organism that can produce nitrates from nitrogen gas this is the first algae/bacteria to bloom in water. As enough nitrates is produced nitrate consuming algae will be able to grow and make the right conditions for other organisms. Clever earth right?

 

[Boomer]

I think you might be wrong about RR only effecting phytoplancton Boomer

No you misunderstood what I said. The RR ratio he gave is for phytoplankton, i.e., C:N = 106:16. Cyano will have a different RR. The RR for phyto is not the same for zoo, which will be different for cayno and different for macro algae and different for coral, etc., etc. They all have a different RR other than C:N = 106:16.


It is for Phytoplankton and Phytoplankton only. It will be ***different for x, y or z coral, x, y or z Algae, Zooplankton etc..

 

[stony_corals]

brad, while I think we all understand what you are saying, like Randy and Boomer point out, each organism will have a different RR, and so trying to be that precise may not be the best way to lower nutrients (N and P) through manipulation of organic carbon additions. There has been some work done to determine RR for macro and some micro algaes....

I think the key value to RR for us is simply understanding that nutrient limitation IS possible, especially considering all the technology in the hobby. There were a series of articles about nutrient levels in Coral Magazine that were very good, Jorg Kokott was the author. While Jorg wrote that P limitation is fatal in corals, I'd think N limitation is more common of the two.....

My .02....

 

[Genetics]

Re: Redfield ratio

<a href=showthread.php?s=&postid=13193775#post13193775 target=_blank>Originally posted</a> by brad
Before debating how useful this calculation is, I wanted to have you check I am doing the calculation correctly.

If I have 120 gallons of salt water and a gallon of saltwater weighs 8.556 lbs, I have 465,712 grams of water. If the water has 100ppm nitrate, then I have 46.6 grams nitrate. Nitrate is 14/62 Nitrogen by weight, so I have 10.5 grams of nitrogen. If I have 0 grams of useable carbon, and want the redfield ratio is C:N = 106:16, I need to add 70.0 grams carbon. Sucrose is 144 / 342 carbon, so I need to add 165.5 grams of table sugar.

Why do I think this might be useful? So I can hurry up and dump exactly 165.5 grams of table sugar into my reef? No, my nitrates are not 100ppm, my volume is not exactly 120 gallons, and I am not insane. This gives me a testable hypothesis to calculate exactly how much sugar I need to add. Then I can figure out what constant rate to add it, and periodically test my water and see how fast nitrate goes down over that period of time. If my nitrates hit 0 long before the sugar is gone or are too high to be accounted for my input at the end of the period, I will know this calculation is useless. As long as nitrates follow what I expect, then I should be able to calculate how to lower nitrate by water changes and dosing a certain amount of sugar over a certain period of time.

I'm going to agree with everyone else about the redfield ratio. It differs dramatically between species and composition does not equal the direct result of consumption. Some other critiques of your experiment. You have 10g of N at the start but over the duration of the experiment that will go up as you add more food into the tank. Once a utilizable source of carbon is added, could other organic macromolecules be uptaken and used for growth and sustainability? N that isn't detectable b/c it is in complex form will also be floating around. What about rock leach of N? And the kicker, the value of the experiment where the number of trials is equivalent to one (n=1). Meaning, the significance will not be validated. Then you have to factor that 165g of sugar could be detrimental and toxic to corals and fish if added too quickly. Just a thought stemming from this article. http://www.advancedaquarist.com/2008/8/aafeature3

But as a non-scientific experiment you will be able to give insight into whether your hypothesis of sugar addition helped reduce detectable nitrates within your tank is potentially viable. I would give it a go. I would create a liquid solution of sugar with 165.5g and then dose that over a given course of time. It would help start defining how much sugar may be needed to achieve nitrate reduction.

 

[torhav]

<a href=showthread.php?s=&postid=13200677#post13200677 target=_blank>Originally posted</a> by Boomer
The RR ratio he gave is for phytoplankton, i.e., C:N = 106:16. Cyano will have a different RR. The RR for phyto is not the same for zoo, which will be different for cayno and different for macro algae and different for coral, etc., etc. They all have a different RR other than C:N = 106:16.


It is for Phytoplankton and Phytoplankton only. It will be ***different for x, y or z coral, x, y or z Algae, Zooplankton etc.. [/B]

With different RR, do you mean ratio to bloom, or to die?
If this is what you mean, then this is exactly what I mean as well.
I might be way off, but what I have understood is that N ratio of 1:16 is the ratio where the envoronment for cyano/phyto is the worst, and the growt will be at its minimum.
What I believe is that if N ratio is low, cyano will bloom to produce avialible nitrogen to restore the natural RR occuring in the ocean. If N ratio is high, phyto will bloom. When these algae die, they sink to deeper water and take exess nitrates with them. Again, natural RR is restored.

 

[Boomer]

The RR, that is in discussion and that Brad gave is the nutrient limiting value for Phytoplankton, aka RR, which is 16:1, and NOT Cyano or, hair algae, macro algae, zooplankton, corals etc.. Everything that lives has a different RR, to include yourself, if we want to get picky. And it is not N ratio of 1:16 but 16:1 for phytoplankton. Brad is asking or stating he wants to run his tank based on the that ratio of 16:1 which is not going to tell or do much of anything as Not a good way to go. The carbon in plankton will not correspond to what they eat, just like it doesn't in your body. They release a lot of it as CO2.

What we are saying is that if one was to run at tank on a RR it should be some other value other than 16:1

I think you might be wrong about RR only effecting phytoplancton Boomer.

Again, I never said that. I said the RR is defined based on Phytoplankton.

Its real meaning
Redfield ratio or Redfield stoichiometry is the molecular ratio of carbon, nitrogen and phosphorus in ***phytoplankton


What I believe is that if N ratio is low, cyano will bloom


Lets pick at that

No, if it is low there will not be a bloom, growth rates and population density will be reduced as there are less nutrients. Blooms come form higher values of RR, where the nutrients are higher not lower usually. If we *pretend* the RR for Cyano was 16:1 you will have more Cyano blooms at say 17:2 (higher) than at 16:1(lower). If it gets below that 16:1 then there is a die off as there is not enough N and P for them to survive. Cyano are famous for blooming in high P Low N nutrient waters as they can fix nitrogen. And when there is more N and less P you get higher algaes say 18:1. In honesty, you really can't just say lower or higher RR. You have to look at the actual ratio of N. However, in general, cyano will have a much lower N RR than say hair algae. The actually RR for Cyano is really lower usually compared to most other algae and Phytoplanotn of 16:1 IIRC So, if you are saying lower than 16:1 then yes you may get more cyano blooms.


But RR can and is used for other things.



A quick search on RR

Redfield revisited: variability of C:N in marine microalgae and its biochemical basis

Authors: Geider R.1; La Roche J.2

Source: European Journal of Phycology, Volume 37, Number 1, 1 March 2002 , pp. 1-17(17)

Publisher: Taylor and Francis Ltd



Abstract:
A compilation of data on the elemental composition of marine phytoplankton from published studies was used to determine the range of C:N. The N ratio of algae and cyanobacteria is very plastic in nutrient-limited cells, ranging from <5 mol N:mol P when phosphate is available greatly in excess of nitrate or ammonium to <100 mol N:mol P when inorganic N is present greatly in excess of P. Under optimal nutrient-replete growth conditions, the cellular N ratio is somewhat more constrained, ranging from 5 to 19 mol N:mol P, with most observations below the Redfield ratio of 16. Limited data indicate that the critical N that marks the transition between N- and P-limitation of phytoplankton growth lies in the range 20-50 mol N:mol P, considerably in excess of the Redfield ratio. Biochemical composition can be used to constrain the critical N. Although the biochemical data do not preclude the critical N from being as high as 50, the typical biochemical composition of nutrient-replete algae and cyanobacteria suggests that the critical N is more likely to lie in the range between 15 and 30. Despite the observation that the overall average N composition of marine particulate matter closely approximates the Redfield ratio of 16, there are significant local variations with a range from 5 to 34. Consistent with the culture studies, lowest values of N are associated with nitrate- and phosphate-replete conditions. The highest values of N are observed in oligotrophic waters and are within the range of critical N observed in cultures, but are not so high as to necessarily invoke P-limitation. The C:N ratio is also plastic. The average C:N ratios of nutrientreplete phytoplankton cultures, oceanic particulate matter and inorganic N and C draw-down are slightly greater than the Redfield ratio of 6.6. Neither the analysis of laboratory C:N data nor a more theoretical approach based on the relative abundance of the major biochemical molecules in the phytoplankton can support the contention that the Redfield N reflects a physiological or biochemical constraint on the elemental composition of primary production.