Why your aquarium needs nitrates (no3)?

[Dan_P]

I would agree my entire conclusion is based on hobby aquaria and anecdotal observations. However the counter argument, measurable no3, is also anecdotal evidence and directly contradicts all scientific evidence.
This quote from the article above is only one example:
In contrast, Renegar, Blackwelder & Moulding (2008) found that nitrate enrichment (~10 µM) reduced wound healing between ~10–60% depending on the coral species. The disparity in our findings can likely be explained by the lower nitrate concentrations used in our study (~4 µM), which are more environmentally relevant and thus less deleterious to corals.

The study discussed wound healing of Pocillopora meandrina with nitrate addition. At ~10 µM enrichment vs ~4 µM the study found that the lower value increases healing and the higher reduced healing between ~ 10 to 60%. The authors further explain that the lower value is more environmentally relevant. Both test enrichment levels of nitrate are below or nearly below detection on a Salifert hobby test kit at 4 μM = 0.2484 ppm and 10 μM = 0.6210 ppm. Generally speaking the hobbyist when compared to controlled science studies of aquariums and nutrient levels for anything from algae control, coral growth, or limiting factors are not even in the same “universe”.

How do we resolve the contradiction that coral survive or even thrive at 5-50 ppm nitrate if the quoted study is relevant to the aquarium?

 

[Dan_P]

The study above quotes the best research example of nitrate enrichment on coral calcification. It is definitive, absolutely, and without argument. Borneman and Sprung use this study specifically to explain nitrate effects on corals and aquariums in their books.

Here:

Google Scholar

scholar.google.com

Same question about the relevance. Do the effects scale linearly, disappear at higher nitrate concentrations, or are relevant to only certain species? There appears to be a disconnect on the magnitude of the nitrate effect.

 

[BriDroid]

I ran my old nano successfully with Tropic Marin Plus-NP. My N would always test under 2ppm (usually under 0.5ppm) and my P would be around 0.03ppm. Not knowing exactly what’s in the Plus-NP other than organic sources of N and P, but it’s kind of the same idea of what’s being talked about in this post.

In my new 40 gallon, I’m feeding frozen pretty heavily twice a day with an aF4 feeder. That seems to be adding plenty of food for the fish and corals. My N is closer to 3-4ppm and my P is around 0.04ppm.

 

[Tripod1404]

Same question about the relevance. Do the effects scale linearly, disappear at higher nitrate concentrations, or are relevant to only certain species? There appears to be a disconnect on the magnitude of the nitrate effect.

Species or even certain individuals from a specie are a possible explanation. I suspect most captive propagated corals are more resistant to high nutrient conditions, as we unintentionally selected for species and individuals better adapted to high nutrient levels (as ones that were not died, and never got propagated).

As Randy mentioned before, it probably also comes down to most tanks having much higher alkalinity compared to natural sea water. I think we have sufficient anecdotal evidence in the hobby to suggest corals do better with high alk with high N&P, and with low alk in low N&P.

 

[Lasse]

Same question about the relevance. Do the effects scale linearly, disappear at higher nitrate concentrations, or are relevant to only certain species? There appears to be a disconnect on the magnitude of the nitrate effect.

From the article that is much of the basis for the thread creator's theoretical reasoning - the article attached to my post #97

As Randy mentioned before, it probably also comes down to most tanks having much higher alkalinity compared to natural sea water. I think we have sufficient anecdotal evidence in the hobby to suggest corals do better with high alk with high N&P, and with low alk in low N&P.

Yes and I think that the authors have done the same conclusion - from the conclusion part of the article

In order to explain the inhibition of calcification by nitrate, we adopt the second hypothesis of Stambler et al. (1991), that is that algae and host compete for inorganic carbon.

I can´t help my self not to speculate about the reason why these two coral types differ from the Acropora type of corals according to the conclusion around skeleton growth and underlying causes. If the theory about competition for inorganic carbon is close to the truth, then understanding how skeleton formation occurs in the current "solid" corals and among the branching Acropora provides a reasonable explanation. To me, it seems that skeleton formation in the "solid" corals mainly occurs below the tissue - inorganic carbon must therefore pass through the tissue - while skeleton formation among the branching corals mainly occurs at the top - skeleton formation first - tissue afterwards. I.E - the point of formation of the skeleton is in contact with the surrounding water. Now, skeleton formation also occurs under the tissue of these (the branches become thicker over time) but it occurs more rapidly at the tops.

There is another interesting note in the conclusions - my bold

Inhibition of calcification by ammonia in Pocillopora damicornis was reported by Stambler et al. (1991) and by Stimson (1992). The growth rate of Stylophora pistillata determined by buoyant weighing is similarly depressed by NH4 + (C. Ferrier-Pagbs, personal communication). Stambler et al. (1991) interpreted the lower growth rate as due to either a reduced translocation of organic carbon from algae to host, or to increased competition for inorganic carbon between algae, (for photosynthesis) and host (for skeletogenesis)

Sincerely Lasse

 

[Dan_P]

I’m willing to accept that this study may be correct (despite a large number of all sorts of single biological studies being overturned later), but if skeletogenesis is the only concern, why is there not an equally strong criticism of having pH at 7.9 or alk at 7 dKH instead of pH 8.4 and alk of 10 dKH?

I would also note that they blame it on lack of available carbon, which perhaps is overcome at an alk of 9 dKH rather then the natural level in the 6’s.

This a good time for a lessons learned exercise.

Some time ago, you posted an idea about observations and interpretation. The idea is that when we read about observations made by aquarists, we might generally accept them as valid. Where critical thinking and skepticism are required is in analyzing the interpretation of the meaning or cause the observation. This concept is also applied when someone quotes a scientific paper: accept the quote, question the interpretation of how it applies the aquarium. The discussion in this post about whether nitrate harms coral is a good example. Facts were quoted correctly but the interpretation was incomplete and not correctly put into the context of an aquarium. This happens often when results from studies of the ocean and coral reefs are interpreted as being transferrable to aquaria. The discussion around dinoflagellates that invaded this post is pure conjecture.

A second lessons learned is the effect of one factor. Rarely is life influenced by only one factor. It is more likely that factor times the setting of another factor plus the setting of a third fact, etc. That is why discussions of what causes dinoflagellates are too simplistic.

A final observation is how well this thread reached what appears to be the best view of nitrate and coral growth.

 

[CHSUB]

Do you do spot feeding on your sun coral? If so - do you have sun corals in spots there it is impossible to spot feed?



Sincerely Lasse

Yes I “spot” feed about 1/2 cube daily of frozen, and with a small aquarium all areas are accessible. I also spot feed all corals daily a mixture of RS ab+ and reef Roids. This might be a reason I’m so comfortable with low nutrient levels. Specifically with po4, I had levels undetectable with Hanna and below 0.1 ppm with photometric ICP for about a year. I view feeding coral animals necessary and equal to feeding fish in proper care. I have moved away from not feeding coral animals directly and relying on zooxanthella or passive feeding solely for nutrition. Feeding all animals directly should be included in good management, especially animals that are not mobile like corals.

 

[CHSUB]

Same question about the relevance. Do the effects scale linearly, disappear at higher nitrate concentrations, or are relevant to only certain species? There appears to be a disconnect on the magnitude of the nitrate effect.

How do we resolve the contradiction that coral survive or even thrive at 5-50 ppm nitrate if the quoted study is relevant to the aquarium?

These are good questions. I believe simple that the hobbyist might be unaware of the negative effects as they are, in many cases, only observable with sensitivity measurements. However I’m not denying or debating the magnitude of the effects, as effects might be very small in many cases.

 

[Dan_P]

These are good questions. I believe simple that the hobbyist might be unaware of the negative effects as they are, in many cases, only observable with sensitivity measurements. However I’m not denying or debating the magnitude of the effects, as effects might be very small in many cases.

Good points

 

[Lasse]

Feeding all animals directly should be included in good management, especially animals that are not mobile like corals.

I´m not sure about that when you deal with corals that relay on photosynthesis from their zooxanthellae. Sun coral need to be feed - but in my aquarium is my colonies of sun coral that not get spot feeded the largest. I spot feed one colony with adult brine shrimps. Never ever used any "coral" food.

Interesting reports according Darwin's Paradox

Since my beginning as reefer and holding corals I always has said that it would be very strange from a biological energy conservation point of view if not the coral animal eat and digest at least a part of the algal residents in their tissue. Many has understand that the coral animal must in one...

www.reef2reef.com

Sincerely Lasse

 

[CHSUB]

I´m not sure about that when you deal with corals that relay on photosynthesis from their zooxanthellae. Sun coral need to be feed - but in my aquarium is my colonies of sun coral that not get spot feeded the largest. I spot feed one colony with adult brine shrimps. Never ever used any "coral" food.

Interesting reports according Darwin's Paradox

Since my beginning as reefer and holding corals I always has said that it would be very strange from a biological energy conservation point of view if not the coral animal eat and digest at least a part of the algal residents in their tissue. Many has understand that the coral animal must in one...

www.reef2reef.com

Sincerely Lasse

I read the study you posted in your thread and some of the thread. The study shows corals surviving and thriving with inorganic nutrients only, however I don’t believe this is relevant in a typical hobby reef aquarium. I posted an article exploring “pulse” vs “press” nutrients where the corals thrived under pulse nutrients, similar to ocean reef that experience fish waste and nutrient up-welling. The corals responded negatively to “press” nutrients or constant higher nutrients. Your study with just inorganic nutrients was conducted with “pulse” nutrients and not “press” that would be typical in a reef aquarium with measurable high nutrients.

From the study:
“Corals exposed to dissolved inorganic nutrient pulses grew about 3.7-fold more than the controls”
“By the end of the 2-h spiking treatment, the tanks were removed from the system and the corals were lifted from the treatment tank and washed by dipping in a tank with system water to remove residual nutrient enriched water”

And the study, ‘pulse vs press’:

https://www.nature.com/articles/s41598-021-92276-y.pdf

Your study used a real world example (bird poop) that showed extra growth when exposed to “higher” nutrients. The “high” values are the bottom of Salifert Hobby testing resolution and might show undetectable. The low value was 0.00062 ppm no3!!! The high value, imo, would get the incorrect label “nitrogen limited” by many hobbyists.

I believe Delbeek used the same study to prove nutrient ratios are an important factor in coral and aquarium healthy.

“Close to the shore of seabird islands, NO3concentrations can reach values as high as 10–20 μM whereas measurements at reference sites with low seabird densities28,49 can return values in the range between 0.01 and 0.73 μM”

 

[KrisReef]

There is no "balance" or ratio between the two. Most of us try to keep those levels as a way to make sure organisms in our tanks have enough to "eat"

I have been trying to figure out why some things just dont seem to have an apetite to strat growing?

 

[Lasse]

rom the study:
“Corals exposed to dissolved inorganic nutrient pulses grew about 3.7-fold more than the controls”
“By the end of the 2-h spiking treatment, the tanks were removed from the system and the corals were lifted from the treatment tank and washed by dipping in a tank with system water to remove residual nutrient enriched water”

Ju must stop to read scientific papers like the Devil reads the Bible! What you describe was a sub experiment with radioactive labeled nutrients in order to show that the nutrients really come from the water and into the animals tissue and was done only for three of the species.

To test our hypothesis that the N and P responsible for sustaining host growth in our experiments was supplied by the symbionts, we conducted a stable isotope labelling experiment. Three coral species (Euphyllia paradivisa, A. polystoma and S. pistillata) were exposed to daily 2-h pulses

In the main longtime experiment - that last for 6.5 months (195 day) had a constant higher nutrient concentration compared with the control - 12µM NO3 (control 0.7 µM) and 3 µM PO4 (control 0.13 µM) In mg/L 0.75 mg/L NO3 and 0.285 mg/L PO4 (0.043 and 0.012 for control

Corals were kept in nutrient-replete conditions ([NO3] ≈ 12 µM, [PO4] ≈ 3 µM), simulating nutrient environments that have been previously described for reefs with increased coral growth rates

You can find the description of the Methods here

The reason why I brought up this article was not for discuss concentrations of nutrients - it was because you state the following which this article debunk

Feeding all animals directly should be included in good management, especially animals that are not mobile like corals.

The devil it still here

however I don’t believe this is relevant in a typical hobby reef aquarium. I posted an article exploring “pulse” vs “press” nutrients where the corals thrived under pulse nutrients, similar to ocean reef that experience fish waste and nutrient up-welling. The corals responded negatively to “press” nutrients or constant higher nutrients. Your study with just inorganic nutrients was conducted with “pulse” nutrients and not “press” that would be typical in a reef aquarium with measurable high nutrients.

Your linked article did not deal with NO3 at all. The study was about NH3/NH4 and PO4

The symbiotic coral Acropora intermedia was grown for 7 weeks under continuously elevated (press) levels of ammonium (14 µmol L−1) and phosphate(10 µmol L−1) as separate and combined treatments, to discern the individual and interactive nutrient effects.

In mg/L will it correspond to 0.25 mg/L NH3+NH4 and 0.95 mg/L PO4. Not normal concentrations in reef aquaria - IMO. Thought - the article may indicate an answer to those that dose NH3/NH4 - do it in pulses

I did a search in the article - could not find any details about alkalinity but it seems like the water around Heron Island has an alkalinity between 6.1 to 6.6 dKH. It means that is not possible to rule out the theory of competition between the zooxanthellae and the calcination process for inorganic carbon - instead it gain some support - IMO and even the authors seems to think the same

Overall,under permanently elevated ammonium and phosphate A. intermedia allocated resources towards tissue grow that the expense of skeletogenesis

Sincerely Lasse

 

[CHSUB]

Ju must stop to read scientific papers like the Devil reads the Bible! What you describe was a sub experiment with radioactive labeled nutrients in order to show that the nutrients really come from the water and into the animals tissue and was done only for three of the species.



In the main longtime experiment - that last for 6.5 months (195 day) had a constant higher nutrient concentration compared with the control - 12µM NO3 (control 0.7 µM) and 3 µM PO4 (control 0.13 µM) In mg/L 0.75 mg/L NO3 and 0.285 mg/L PO4 (0.043 and 0.012 for control


You can find the description of the Methods here

The reason why I brought up this article was not for discuss concentrations of nutrients - it was because you state the following which this article debunk



The devil it still here




Your linked article did not deal with NO3 at all. The study was about NH3/NH4 and PO4



In mg/L will it correspond to 0.25 mg/L NH3+NH4 and 0.95 mg/L PO4. Not normal concentrations in reef aquaria - IMO. Thought - the article may indicate an answer to those that dose NH3/NH4 - do it in pulses

I did a search in the article - could not find any details about alkalinity but it seems like the water around Heron Island has an alkalinity between 6.1 to 6.6 dKH. It means that is not possible to rule out the theory of competition between the zooxanthellae and the calcination process for inorganic carbon - instead it gain some support - IMO and even the authors seems to think the same



Sincerely Lasse

Thank and some good comments.

I made a change to the statement below in bold:

“ IMO Feeding all animals directly should be included in good management, especially animals that are not mobile like corals.”

 

[CHSUB]

In the main longtime experiment - that last for 6.5 months (195 day) had a constant higher nutrient concentration compared with the control - 12µM NO3 (control 0.7 µM) and 3 µM PO4 (control 0.13 µM) In mg/L 0.75 mg/L NO3 and 0.285 mg/L PO4 (0.043 and 0.012 for control

You can find the description of the Methods here

You posted “here” of the long time experiment. The experiment was done under “pulse” nutrients additions: “the water in each treatment tank was spiked with 1 ml of 15N-enriched (10%) NO3 and PO4 stock solutions, to reach an average concentration of ~10 µm NO3 and ~3 µM PO4. A second spike was delivered after 1 h”

As noted, and you pointed out, the actual concentration of no3 in the high nutrient test was 0.75 ppm, which is barely readable by Salifert. Many hobbyists in the high no3 camp would consider this no3 level limited.

I will agree this experiment gives evidence that corals can perform well only relying on zooxanthella. However, the no3 is still very low by hobby standards. Does this dynamic change at a 400% increase in no3, which would only bring the level to 3.0 ppm no3. I find this study fascinating, however when the hobbyist uses it as in example with no3 levels of 20 ppm, for example, imo its usefulness is vastly diminished.

 

[jeremie]

Although I have yet to see any peer reviewed studies that test nitrate levels higher than 5 ppm, I personally don’t think most corals really care much about the actual concentration once it is over 1 ppm. From a coral’s perspective, 50 ppm might not be that different from 5 ppm.

Nitrate, like other charged ions, cannot diffuse directly across the cell membrane, so it has to be taken up by transporter proteins or ion channels. The uptake of these ions generally follows Michaelis–Menten kinetics, where the uptake rate increases with concentration, but once the transporters are saturated, the uptake rate will not change much even if the concentration keeps rising. Unlike phosphate, which can bind to or react with many substrates, nitrate generally is not a very reactive ion on its own, so I do not really expect it to do much just floating around in the water.

Most of the research on nitrate uptake kinetics in corals seems to indicate that uptake rates generally saturate at levels below 1 ppm. Although I certainly cannot rule out the possibility that some species might saturate at higher concentrations, I do not see much reason to believe they would be drastically different from the species that have already been tested.

Here are two papers on this topic if you are interested:
Nitrate uptake by the reef coral Diploria strigosa: Effects of concentration, water flow, and irradiance
High phosphate uptake requirements of the scleractinian coral Stylophora pistillata

 

[CHSUB]

‘‘Since both organic and inorganic sources of N and P are overall scarce in oligotrophic tropical waters10, the symbiotic lifestyle offers corals a truly competitive edge over exclusively heterotrophic animals that rely solely on N and P in organic forms, or exclusively autotrophic plants such as macroalgae that are restricted to N and P in dissolved inorganic form.”

Quote from study that demonstrates low inorganic nutrients can indeed limit algae while not affecting corals…just food for thought!

 

[Randy Holmes-Farley Verified Community Expert]

‘‘Since both organic and inorganic sources of N and P are overall scarce in oligotrophic tropical waters10, the symbiotic lifestyle offers corals a truly competitive edge over exclusively heterotrophic animals that rely solely on N and P in organic forms, or exclusively autotrophic plants such as macroalgae that are restricted to N and P in dissolved inorganic form.”

Quote from study that demonstrates low inorganic nutrients can indeed limit algae while not affecting corals…just food for thought!

That is largely false.

Many marine algae contain externally anchored alkalinity phosphatase to break phosphate off of organic compounds and take it up. Thus, it may be impossible to limit marine microalgae by reducing phosphate without hurting corals.

Similarly, many marine algae can take up or use externally anchored enzymes to use various organic forms of nitrogen to survive in nutrient poor conditions, including amino acids, nucleic acids, and urea.

 

[Lasse]

You posted “here” of the long time experiment. The experiment was done under “pulse” nutrients additions: “the water in each treatment tank was spiked with 1 ml of 15N-enriched (10%) NO3 and PO4 stock solutions, to reach an average concentration of ~10 µm NO3 and ~3 µM PO4. A second spike was delivered after 1 h”

As noted, and you pointed out, the actual concentration of no3 in the high nutrient test was 0.75 ppm, which is barely readable by Salifert. Many hobbyists in the high no3 camp would consider this no3 level limited.

I will agree this experiment gives evidence that corals can perform well only relying on zooxanthella. However, the no3 is still very low by hobby standards. Does this dynamic change at a 400% increase in no3, which would only bring the level to 3.0 ppm no3. I find this study fascinating, however when the hobbyist uses it as in example with no3 levels of 20 ppm, for example, imo its usefulness is vastly diminished.

I agree with Randys comments above and also the authors do that - se their comments in my last quote in this post. I have been working with this post for 6 hours and therefore Randy was faster

The article shows that the coral animal can survive and grow very well in nutrition concentration of around 0.75 mg/L NO3 and 0.285 mg/L of PO4 compared with the control that has what aquarists think is normal in the wild.

It is not dealing with higher values - but this does not mean that higher values give the same, better or worse growth - it just say that during this condition all tested corals growth better than control (0.043 and 0.012 mg/L NO3/PO4)

‘‘Since both organic and inorganic sources of N and P are overall scarce in oligotrophic tropical waters10, the symbiotic lifestyle offers corals a truly competitive edge over exclusively heterotrophic animals that rely solely on N and P in organic forms, or exclusively autotrophic plants such as macroalgae that are restricted to N and P in dissolved inorganic form.”

Quote from study that demonstrates low inorganic nutrients can indeed limit algae while not affecting corals…just food for thought!

This quote is from the same article and they have not demonstrate that low inorganic nutrients can indeed limit algae while not affecting corals - however they state this in the discussion part of the article. You have the example in your own aquarium - you boasted that your sun corals were thriving and their growth rate is exactly what you get if you don't give your photosynthetic corals light and nutrition. I can even imagine that you get worse growth in your photosynthetic corals if you force them to be completely heterotrophic because the food they capture has to go to both the coral animal and the symbiont's survival and growth. IMO - If you only uses the two outer endpoints (heterotrophic or autotrophic growth only) in corals that have zooxanthellae. - you get the best growth in pure autotrophic conditions.

The article did not do an experiment with the combination of heterotrophic and autotrophic conditions in the lab- as it is in nature.

However - they did a study in the wild. The NO3 concentrations was up to over 1 mg/L and phosphate around the figures for the long time lab experiments ~0.28 mg/L PO4. Excuse the long quote with my bold. Main source
here

Applying a geochemical source mixing model49 and using the δ15N values of guano and zooplankton as endmembers, we find that around 50% of coral host N can be traced back to guano-derived N and thus to the primary uptake by the symbionts. Consequently, N acquisition by heterotrophic feeding on zooplankton contributes less than 50% to the N budget of the coral host. Across a multi-year in situ tagging experiment, the area of Acropora colonies showed growth rates about two times higher in waters surrounding islands with high seabird densities compared with the reefs around islands without large seabird colonies (Fig. 4c). These data are consistent with the approximately threefold increase in linear extension of Acropora after transplantation to NO3-enriched reef water close to seabird colonies28, revealing the direct benefits seabird-mediated nutrient enrichment to coral growth at the ecosystem scale. In the absence of alternative known major translocation mechanisms, the symbiont digestion pathway established by our laboratory experiments offers a plausible explanation for the significant accumulation of seabird-derived nitrogen by the coral host, indicative of a major contribution symbiont digestion to the nitrogen budget of coral animals in natural reefs.

This means if you compare a mixed feeding in systems with low nutrient concentrations and mixed feedings in system with high nutrient concentration - this study indicates that growth is at least twice as great when the water contains elevated inorganic concentrations of nutrients in addition to particulate food in nature

Instead of cherry picking quotes that seems to fit into your agenda - try to read the whole article and especially this part

There you can read things like this - as usually - my bold

Our experimental findings show that coral animals can farm their symbionts and feed on the symbiont stock to access a pool of dissolved inorganic N and P in the surrounding waters that would not otherwise be accessible to them (Fig. 5). If enough dissolved N and P is available, feeding on symbionts represents a mechanism to fully meet the nutrient demands of coral growth. Under these conditions, the corals function in essence similar to fully C-, N- or P-autotrophic organisms such as plants, algae and photosynthetic prokaryotes. When food and nutrient supplies are too low, the continued consumption of symbionts at a constant digestion rate can act as an emergency measure to maintain their productivity for a limited period until the symbiont stock is depleted and the corals bleach (Figs. 1 and 3). However, if the corals cannot take in N and P in quantities that meet the demand of both partners of the symbiosis50, feeding on their symbionts in nutrient-depleted waters can eventually lead to coral death

But here is a very interesting thing

Of note, growth of Acropora sp. is enhanced by a phytoplankton-dominated diet, indicating that their digestive machinery is indeed well-suited to process algal cells

I dug up this article - and I will comeback later on because there are findings in it that may rock the fundings of the necessary to feed your acropora - with one exception

Sincerely Lasse

 

[TokenReefer]

That is largely false.

Many marine algae contain externally anchored alkalinity phosphatase to break phosphate off of organic compounds and take it up. Thus, it may be impossible to limit marine microalgae by reducing phosphate without hurting corals.

Similarly, many marine algae can take up or use externally anchored enzymes to use various organic forms of nitrogen to survive in nutrient poor conditions, including amino acids, nucleic acids, and urea.

This is really interesting. I wonder which algaes. I can see GHA creating this type of micro environment as it easily traps detritus and food and that always seems, to feed it vs say valonia and it's structure. I think blowing the algae clean helps to at maybe slow it down