Nitrate increase oxidative stress

[JonasRoman]

So, the recurring subject. Nitrate. My personal opinion is since long time back, that nitrate is an indicator of nitrogen cycle balance, and we have no primary benefits of having any nitrate at all. Nitrogen is needed for the zooxanthelle, and thats more beneficial in form of ammonium. Maybe that's a partial reason why coral tanks benefits having some fish (breathing ammonium)?

I have red this wonderful article based on a very serious experiment. I try to summarise the study here and do some conclusions.

Here is my summary:

Based on this research, it is clear that nitrate itself is not beneficial for corals, not even in low concentrations. Even though corals and their symbiotic zooxanthellae require nitrogen to survive, the form of this nitrogen is absolutely crucial for the coral's health. While a supply of ammonium has been shown to benefit the coral by improving its energy metabolism and protecting against oxidative stress, nitrate has an opposite and directly harmful effect.
In light of this, it seems strange, (and maybe based on incompetence?) that companies sell nitrate as coral nutrition. Although many corals can survive in water where nitrate is not extremely low, the study confirms that a nitrate addition of only 3 µM (which corresponds to approximately 0.19 ppm) leads to significant oxidative stress and a reduced aerobic capacity in the coral. This oxidative stress makes the coral more susceptible to coral bleaching, especially during temperature increases.
Furthermore, the negative effects of nitrate are particularly severe when phosphate levels are low. The research emphasizes that an increase in nitrate can lead to changes in the algae's lipid composition and a destabilization of their membranes.

In summary, although nitrogen is certainly vital for the coral's symbionts, this need should be met through ammonium (or urea) rather than nitrate, as nitrate actively contributes to a physiological imbalance and an increased risk of coral bleaching and oxidative stress, already at reasonable low levels.

Jonas Roman

 

[JonasRoman]

Some more comments and notes:
1) The corals did NOT fully recover in all aspects, (phase 3), for instance calcification rate was not restored) after exposed to nitrate 0.19 ppm.
2) Even with no thermal stress there happened bad things when exposed to nitrate, but it was further increased with addition of thermal stress.
3) Even if po4 was low it was not limiting.

 

[Randy Holmes-Farley Verified Community Expert]

These are my added comments:

1. I agree that I might prefer to have little nitrate and adequate levels of preferred N sources, such as ammonia, urea, and organics, both particulate and dissolved of an appropriate composition. HOWEVER, since no one can know if they have adequate levels of these at any point in time in a reef tanks life without trying it and seeing if they observe problems, it is prudent for most reefers to have sufficient levels of nitrate to ensure that N is not a significant limitation to coral growth. The easier route is just to have adequate nitrate, and not risk "finding" those problems.

2. I have not seen any data or reef tank examples to convince me that high levels of nitrate are going to cause any issues that a reef aquarist can detect, while insufficient N very clearly does. Some great tanks have 100+ ppm of nitrate without apparent issues, and in at least one case, lowering it over time did not result in any obvious improvements.

3. Scientific studies that demonstrate issues with elevated nitrate (such as making thermal stress worse) do not always supply other sources of N, forcing the corals to consume nitrate. That may not always be the case, but when it does, it takes away from the conclusion that elevated nitrate would necessarily be a problem in a real reef tank. Example study that just gives them either ammonia or nitrate, but not both together:

https://pubs.acs.org/esthag/article/60/2/1699/5082106/Nitrate-Aggravates-While-Ammonium-Mitigates

4. If reefers are not having problems with bleaching from thermal stress (which is not very common and controllable; I've never had it happen in one of my tanks in decades of keeping them), is the fact that nitrate compounds the thermal stress issue a real concern?

5. Since I do not recommend low levels of phosphate, and advise folks to dose if it exists, the compounding of nitrate issues when phosphate is low is not, IMO, a reason to lower nitrate but to raise phosphate. Dosing phosphate is also often easier than lowering nitrate.

6. IMO, many reefers with adequate N and P would be best served by spending time and money on issues other than adjusting nutrients downward. :)

Overall, this is my suggestion, and the article linked below gives examples of great tanks with both high and low phosphate and nitrate:

Randy’s Thoughts on Nutrient Target Ranges​

https://www.reef2reef.com/ams/randy’s-thoughts-on-nutrient-target-ranges.1087/

from it:

4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

• Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
• Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
• Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
• Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
• Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
• Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.

 

[EnterName]

Following, I already see that this is going to be a controversial thread

The high nitrogen / low phosphorus debate is more or less still ongoing and probably hard to settle so I don't think it makes too much sense starting there again, especially since I agree with your verdict in the thread if I understood it correctly.

But I think it's quite easy to explain why nitrate is being sold instead of ammonia. You simply need to explain too much to the average customer. On one hand you are trying to sell them bottled bacteria to oxidize all that "bad and dangerous" ammonia to nitrate so their fish are safe, but then you start selling them bottled ammonia? Marketing and Sales is going to hate you for that

 

[JonasRoman]

1. I agree that I might prefer to have little nitrate and adequate levels of preferred N sources, such as ammonia, urea, and organics, both particulate and dissolved of an appropriate composition. HOWEVER, since no one can know if they have adequate levels of these at any point in time in a reef tanks life without trying it and seeing if they observe problems, it is prudent for most reefers to have sufficient levels of nitrate to ensure that N is not a significant limitation to coral growth. The easier route is just to have adequate nitrate, and not risk "finding" those problems.

I think its unlogic to be satisfied with high NO3 as an indirect sign of also having the good ammonium. The study is clear and give us knowledge what bad NO3 can do with the coral. Even if coral may stand it, its never beneficial. So why dont concern? Also, when you have fish , feed, and not runing carbon source, you can be sure you have a continous ammonium production for the zooxanthelle. SO, lack of nitrate wouldnt worry me.

 

[JonasRoman]

2. I have not seen any data or reef tank examples to convince me that high levels of nitrate are going to cause any issues that a reef aquarist can detect, while insufficient N very clearly does. Some great tanks have 100+ ppm of nitrate without apparent issues, and in at least one case, lowering it over time did not result in any obvious improvements.

I have seen many tanks where corals dye (bleaching), and those tanks have high nitrate, 50 ppm, ish. I dont say its because of that, but number of cases are many. And many many cases where a coral sudden dye and we do not know why, occurs every day. How do you know that it wasnt because of nitrate? Especially summertime and in a warm period.

 

[JonasRoman]

3. Scientific studies that demonstrate issues with elevated nitrate (such as making thermal stress worse) do not always supply other sources of N, forcing the corals to consume nitrate. That may not always be the case, but when it does, it takes away from the conclusion that elevated nitrate would necessarily be a problem in a real reef tank. Example study that just gives them either ammonia or nitrate, but not both together:

Agree, but that is still a remarkable finding that nitrate "solely" have this negative impact. yes, it can be opposite by adding ammonium, but that doesnt take away the negative effect of nitrate. It just say that there is protectice mechanism. If I have an umbrella and therefore not getting wet, its still raining.

 

[JonasRoman]

4. If reefers are not having problems with bleaching from thermal stress (which is not very common and controllable; I've never had it happen in one of my tanks in decades of keeping them), is the fact that nitrate compounds the thermal stress issue a real concern?

Disagree. There are thousand of reports of reefers with issues, including me and you and all of us. More problem than not problem. RTN, STN, corals that looses zooxanthelle etc. Thats why we are here, to find out and help and understand. This is not same as all this is becasue of nitrate, ofcourse not. But some of the cases maybe?

 

[JonasRoman]

5. Since I do not recommend low levels of phosphate, and advise folks to dose if it exists, the compounding of nitrate issues when phosphate is low is not, IMO, a reason to lower nitrate but to raise phosphate. Dosing phosphate is also often easier than lowering nitrate

Agree, and artice say same: Low Po4 is very bad, and even more bad if NO3 is high. And yes, in a situation with low PO4 and semihigh NO3, I would def focus on raise PO4 first as ultralow PO4 is more direct harmfull as its= direct starvation. High NO3 is not, its long term negative metabolic sideeffects.

 

[JonasRoman]

6. IMO, many reefers with adequate N and P would be best served by spending time and money on issues other than adjusting nutrients downward. :)

In general I have same opinion. I would not chase down NO3 when its still quite low, but I would never dose it, and I would try to increase denitrification capacity when above 5 ppm.

 

[JonasRoman]

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