Light, Alkalinity, Nutrients.

[mcarroll]

Anyone concerned about pH and coral skeletons:
Biological control of aragonite formation in stony corals

I put a couple of good quotes on the blog, but the whole article is available so please read!

Here's another quote from the article's conclusion:

[Corals] survived the Paleocene-Eocene Thermal Maximum, which was associated with a very large increase in atmospheric carbon dioxide (34). Indeed, scleractinian corals radiated in the Eocene (35).

 

[Hans-Werner]

Other issue is with dinos. Every time I bring PO4 down to below 0.05 , I see an increase in dinos. I bring PO4 to around 0.15 and dino slowly goes away. it seems almost like i am able to replicate dino on/off situation at will by just controlling phosphates.

To me this sounds more like cyanobacteria. Did you verify with a microscope it are dinoflagellates?

We were beta testing some of Knop's giant calcium reactors (not sure if these monsters ever made it to market) and, if my recollection is correct of circumstances some 20 years ago, the dKH jumped about 2 full units (that is, ~7 to 9) overnight. We didn't see any stress reactions (polyp withdrawal, mucus production, bleaching, etc.) My point is that we didn't lose any of perhaps 20 coral genera (hundreds of frags, perhaps a 100 species) we had in this system. All I am suggesting is that a sudden jump in alkalinity didn't cause any adverse effects that we could determine visually, and certainly no tip burning. Do I recommend doing this - of course not. But we did and it was part of our learning curve.

With a calcium reactor filled with coral rubble you will always have a phosphate supply together with the KH supply. I think in relation to the needs of the corals they throw out even more phosphate than KH. I think phosphate is the most critical nutrient for corals, much more than nitrogen. With a calcium reactor filled with coral rubble you will never phosphate limit the corals no matter how high the alkalinity (at least almost so). In tanks with calcium reactors usually the phosphate rises when the KH stays the same. In fact the phosphate alone can make the KH rise since phosphate inhibits the aragonite (or maybe calcium carbonate in general) precipitation. With a calcium reactor you only get in trouble when you start to lower phosphate. I knew a tank (and its owner) back then with good Acropora growth. The owner always wanted to keep the KH at 9 at least but he also wanted to have low phosphate concentrations and used Rowaphos. Always when doing this he got STN (it wasn´t so slow, the corals lost part of their tissue quite rapidly) from the base of the Acroporas and he lost a good part of living tissue he won before by growth. He wanted to know what he can do. I told him to accept either a lower KH or a high phosphate concentration but he insisted that it should be possible to have both. Later I moved away and meanwhile he died as I have heard.

 

[Hans-Werner]

Just one more sentence: The fact that a calcium reactor besides calcium and bicarbonate also supplies phosphate is in my eyes the cause why coral frags grow especially rapid with this kind of calcium supply, not the elevated KH only.

 

[Diesel]

Interesting. I have the first paper in my library, and I need to review the referenced Advanced Aquarist article. So, we could test the latter hypothesis - has anyone seen alkalinity burn in an unskimmed tank?

That's a question for @Cruz_Arias as he ran some systems without a skimmer and grew corals like weed, well he did the MNB but that's a different subject.

BTW, reading this post I need to dig up my notes from two years ago when my frag tanks ran unknowingly on ALK at 5 or below, no PE on SPS but color still ok.
Only draw back I ever experienced in the last 30 years is that high ALK "11 or higher" never was a good thing no matter where my other N&P were, I did discussed that with Mike P as he ran on his systems the high N&P and high ALK, it must be the miracle mud

 

[CodyRVA]

So, as it pertains to ALK... white tips/bleaching would indicate a lack of nutrients and browning would indicate high nutrients? Is this this straight forward or are there nuance scenarios where this won't always be one or the other?

I asked before, but no one chimed in... what causes a stony coral to get white tips, bleach and continue to bleach out even after parameters are realigned?

 

[Hans-Werner]

There are nuance scenarios. When colors of the corals get very pale it is most likely a lack of nitrogen and more specific of ammonium or amino acids because with only nitrate as nitrogen source corals are still quite lightly colored. This is what the zeolith methods make use of. Zeolith adsorbs ammonium but the nitrate is not adsorbed.

It is phosphate deficiency that makes the burned tips while the color of the coral tissue stays relatively dark.

 

[bubbaque]

@Hans-Werner why do you believe your friend ran into issues when he would use rowaphos, even if he was giving the corals a constant supply of phosphate with a calcium reactor?

 

[Hans-Werner]

Because the phosphate concentration in the tank was nevertheless lowered by the Rowaphos. The phosphate concentration available to the corals was lower and in combination with the high alkalinity this resultet in the STN from the base.

 

[mcarroll]

I asked before, but no one chimed in... what causes a stony coral to get white tips, bleach and continue to bleach out even after parameters are realigned?

I'm not sure if this was answered and I'm recycling (call me out!)....or if I read this last night when I was up too late.....or maybe this was even something I read a while back and I've had posted to my blog (bunch of stuff like this on there). And let me know if I misunderstood the question...

But here goes...

The white tips are apparently dino-free so that the coral isn't killed by photosynthesis. (I also don't think bleached is the right term since there were no dino's there to begin with.)

The "dark meat" where all the dino's are concentrated is kept mostly-shaded by upper branches so that overall colony exposure isn't too high. (Trees apparently do the same thing, maybe better, via random orientation of their leaves. The effect of these strategies is significant.)

Self-shading like this is apparently either the major reason or one of the major reasons why branchy corals are branchy. It's an energy-dispersive and energy-blocking shape.

I think this may be why branchy corals seem more sensitive to lighting and flow changes too though. Perhaps in branchy corals some of their extreme-short-term adaptability is sacrificed to their "superior" skeletal design. Consider that along with how we think of "most corals" being protected by some relatively impermanent skin pigments and where their shape is not so "energy reflective".

Compare with funnel shaped corals, which would include most plating and tabling shapes. Funnel shaped corals cause detritus to settle inside of them (a food source), even at the cost of a little tissue necrosis around the settling zone. And with a funnel shape they essentially open themselves up to as much sunshine as they can get. (They know frequent surges from storms, etc will clear them out too, so it's a well-thought-out design. )

 

[mcarroll]

So, as it pertains to ALK... white tips/bleaching would indicate a lack of nutrients and browning would indicate high nutrients? Is this this straight forward or are there nuance scenarios where this won't always be one or the other?

It's not quite that simple because nutrient history plays a significant role.

For example, are nutrient levels high, or have they spiked? Two different things because of the time interval and related effects.

There are some other goodies on the blog for this too, but here's one of the newer links that should help and might be interesting:
Nitrogen cycling in corals: the key to understanding holobiont functioning?

 

[chefjpaul]

It's not quite that simple because nutrient history plays a significant role.

For example, are nutrient levels high, or have they spiked? Two different things because of the time interval and related effects.

There are some other goodies on the blog for this too, but here's one of the newer links that should help and might be interesting:
Nitrogen cycling in corals: the key to understanding holobiont functioning?

I was just going to comment on this, what is a "spike" relative to time.
Now are we seeing alk short term effects vs. Long term high kh along with long term ULN causing issues.
There are a lot of variables including Par etc. Included.

 

[mcarroll]

If nutrients go up fast enough to cause an algae bloom, then at least IMO it was a spike. Bloom is clearly different than ordinary growth, at least in most cases.

 

[Steve Ruddy]

Good question Dana. I which I new who started this rumor as well. I have been keeping reef aquariums for a few years myself and have never had the so called Alk burn from a sudden rise in alkalinity and my systems are always ULN. The only time I have experienced tip burn was recently when I had dosed B-Ionic in un equal parts for several months.

 

[CodyRVA]

If nutrients go up fast enough to cause an algae bloom, then at least IMO it was a spike. Bloom is clearly different than ordinary growth, at least in most cases.

Agreed. This is my main argument for folks who have success with SPS who run high nutrients. I believe them 100%, but I also believe they acclimated the corals to this environment, they didn't go from ULN to high nutrients over night.

I have been keeping reef aquariums for a few years myself and have never had the so called Alk burn from a sudden rise in alkalinity and my systems are always ULN.

I've never had this happen either unless the ALK spike was quite high or if there was something else involved; IE: nutrient spikes. IME running my doser, the only time i've ever experienced a spike in ALK is from something else causing it; my hypothesis: nutrient spikes lead to inactive coral which leads to ALK spikes which leads to... this entire conversation!

 

[Dana Riddle]

Not ignoring anyone! I need some time to give all the material given more than a cursory review and find my old log book. But I'll throw this out for comments - do we really have have a nutrient deficiency if an aquarium is well fed? Isn't it possible that the bacterial conversion of proteins/amino acids to ammonia and hence its utilization is sufficient for zoox? That capture of particulates is enough? That 'farming' of bacteria using coral mucus supplies a constant source of food for some corals (ala Sorokin?) And that the phosphorus cycle converts enough organically-bound phosphorus to ortho-phosphate? That these might not be measurable if the conversion is relatively slow and utilization is rapid? If any of this is true, why would be add nutrients (back to my original question.) Again, I'll review your comments closely and digest the material. Be back soon!

 

[Hans-Werner]

Dana, I have read and I think also understood "Coral Reef Ecology" of Sorokin and I like it very much. I agree with him that corals do bacterial farming and this may be one way to gain phosphate. But he also writes that corals in coral reefs are phosphate limited in their growth and that under low phosphate concentrations they lose (leak) much phosphate, maybe more phosphate than they take up from the water.

I don´t wanna insist that it must be phosphate starvation when the corals get burnt tips or when they show STN from the base under high alkalinity conditions. Especially the latter could very well be a matter of competition for uptake. I am sure there are more alternative explanations. But I am quite sure that there is some kind of negative interaction between high alkalinity/inorganic carbon and phosphate.

 

[Diesel]

Don't close out the possibility of bacterial deceases.
We might looking into one direction as there are many more of course.
30 years ago it was flow and light, than nutrients came in place, followed by dosing and elements.
We still know little about bacterial deceases on corals, especially on SPS.
Good discussion but it will be a long research.
Do we all remember and I never understood really why there were hobbyist advocating to go low to almost 0.0 on nutrients in the N&P just going back five years, and if you mentioned that your dominant SPS tank runs on 7.5ppm ALK you didn't know what you were doing.
That said we came a long way in this hobby and yet a lot of ppl manage to set up a nice systems and have it crash due to losing track on just the basics.

 

[CodyRVA]

All good info, thanks to @Dana Riddle for starting this one. I know you're still digesting all of these comments, but here are my lingering questions. The motivation to ask comes from this thread I created currently monitoring my system that seems to be going through a "bleaching" event. There are many inconsistencies from how coral A has responded compared to coral B.

1.) When a "bleaching" event occurs (whatever you want to call it) why do some coral "bleach" from the base, some from the tips, and some from the sides. Is this specific to the type of coral or the parameters in which that coral is being exposed to?

2.) When a "bleaching" event occurs, why do some go white and others go brown? Again, does this depend on the type of coral or do other things come into play like light and flow?

3.) When issues arise causing a "bleaching event", some coral will have gotten white tips or some die off, but will eventually recover completely, but many don't recover at all. Many more will continue to "bleach" after the problems have been fixed. Why is this? Does this also depend on the coral type, flow, lighting etc?

 

[Diesel]

All good info, thanks to @Dana Riddle for starting this one. I know you're still digesting all of these comments, but here are my lingering questions. The motivation to ask comes from this thread I created currently monitoring my system that seems to be going through a "bleaching" event. There are many inconsistencies from how coral A has responded compared to coral B.

1.) When a "bleaching" event occurs (whatever you want to call it) why do some coral "bleach" from the base, some from the tips, and some from the sides. Is this specific to the type of coral or the parameters in which that coral is being exposed to?

2.) When a "bleaching" event occurs, why do some go white and others go brown? Again, does this depend on the type of coral or do other things come into play like light and flow?

3.) When issues arise causing a "bleaching event", some coral will have gotten white tips or some die off, but will eventually recover completely, but many don't recover at all. Many more will continue to "bleach" after the problems have been fixed. Why is this? Does this also depend on the coral type, flow, lighting etc?

IMO, as you mentioned coral type, flow, lighting you can add to that nutrients.
If you don't have any troubled algae growth you should dose more nutrients.
I will look up a thread if I can find it where this was discussed and corals bounced back even though in the first place the nutrient level was good in the water.

 

[CodyRVA]

IMO, as you mentioned coral type, flow, lighting you can add to that nutrients.
If you don't have any troubled algae growth you should dose more nutrients.
I will look up a thread if I can find it where this was discussed and corals bounced back even though in the first place the nutrient level was good in the water.

Agreed, nutrients is definitely apart of it.

Something else to consider in regards to do dosing nutrients with absence of troubled algae. I've had nutrient spikes and never seen cyano, hair algae, etc., but I have seen a spike in other critters such as spaghetti worms and vermetid snails which i'm told will only thrive if and when proper conditions (nutrients) are available. I guess my point is, just because you don't have those nuisance algaes, doesn't mean the nutrients aren't there? Thoughts?