Do you think mangroves have the potential to considerably raise calcium levels?

[chris_h]

I was trying to think of ways to naturally raise calcium in my tank. I remembered from a vacation in florida that mangroves produce acid and dissolve all of the sand around them. I was thinking of switching the caulerpa in my 70 gallon sump for mangroves. The nutrient removing ability is not really a concern, and it would be neat if I could maintain my calcium this way.

[SteveN]

So where would you get sand to replace that lost to the acid? Seems like that might be more expensive.

[chris_h]

sand is less expensive than the other stuff used to maintain calcium.

[SteveN]

Where do you get your sand, I need to get some of that sand. Around here it is $2 a pound. I get Mrs. Wages for a buck. Another thought, what will the acid production do to the buffer system, alk? Not trying to flame you. Just really curious. If it would work it would be an awesome looking tank.

[MickAv8r]

Unless you had a virtual forest of mangroves in the system it is quite unlikely you will see any benefit. They simply aren't going to dissolve enough sand.

Steve: the acid would essentially react just like a calcium reactor (carbonic acid dissolving aragonite).

For more info about Mangroves I suggest you download and reef Julian Sprung's guide. FWIW he doesn't mention anything about them releasing acid. It could be that since they uptake oxygen through their roots they may release CO2 there as well.

http://www.twolittlefishies.com/images/prod_plants_guide.gif (http://www.twolittlefishies.com/images/mangrove_manual.pdf)

[SteveN]

I can see a parallel to a reactor, but since I have no real idea how they are used, please bear with me. If I am correct, the reactor is outside of the system and the result of the reactor is put into the system. In other words, the acid is not in the aquarium. Is this correct? That is why it doesn't seem like it would be a good idea to me. The acid would be in the system and counteracted before it would have time to work. I don't know, just think out loud.

[Randy Holmes-Farley]

I am not familiar with acid produced by mangroves. I have a few, but I've never looked at them as acid producers.

If they produce acid, it could come in two ways:

1. Acid excreted from the roots. Either CO2 or another acid would help dissolve some of the CaCO3 sand. The pH down in sand beds is already significantly lower than the main tank, and a little more acid may accelerate dissolution. I'd expect this to be a small contribution to a reef tank (as Tom pointed out), assuming that it is real.

2. If it is something that they drop from their leaves, then we are probably out of luck. In a real mangrove setting, these drops may land directly on sand at low tide, and help dissolve the sand. Few of us have tanks big enough to have tides, so the sand is never exposed and won't dissolve under this scenario.

As with a previous discussion about magnesium excretion, there may be differences between the different mangrove species. Consequently, if you are trying something along these lines, make sure that you have the same species as whoever is suggesting that they produce acid.

[olgakurt]

I think this Ca/substrate leaching concept was probably brough over from acid sulfate soil studies in Mangrove areas which I have tried to summarize below from what I recall reading.

As Randy alluded to several requirements must be met for the development of such conditions (formation of iron sulfides):a supply of dissolved sulfate, with concentration greater than 10 mg/L, supply of organic matter, an adequate source of iron, generally oxygen-free conditions, and tidal flushing to remove soluble reaction products.

Such conditions occur in wave-protected mangroves.
Not all acid produced by oxidation of sulfides is released because the acid soil water
can react partly or even completely with the sediments in which it was produced. The reaction
between acid and soil constituents liberates many dissolved metal species. These ions remain dissolved, provided the solution remains acid (pH generally less than 4.5), and can be extremely toxic to plants and gilled organisms.

The reaction of acid with the soil also brings about permanent change to the soil itself. Many of the unconsolidated, back swamp, sulfidic sediments are essentially gels containing up to 80 per cent water and they have a very small capacity to transmit water.

The rate of oxidation of acid sulfate soils determines the persistence and magnitude of acidic outflows. This rate depends on how fast oxygen in the air can move into the soil, the amount and distribution of sulfides in the soil, the distribution of soil water, soil temperature and soil pH, and soil composition.

In areas with vigorous growth and where the unoxidised sediments have low hydraulic conductivity, evapotranspiration can withdraw water faster than it is supplied by inflow
from drains or creeks. This evapotranspiration lowers water tables below the position of the
unoxidised sulfides and exposes them to air. Even in present-day, undrained mangrove communities, oxidation of the newly formed sulfides to sulfuric acid occurs at every low tide,although the acid is neutralised by the subsequent high tide.

I believe the acid can react with the calcium
carbonate to form gypsum (calcium sulfate.

AS pointed out above, it is unlikely any of these conditions are met in captive reef systems.

[Guy]

To summarize OlgaKurt's excellent brief:

Don't throw away your CA reactor!

[Randy Holmes-Farley]

olgakurt:

If I'm understanding the process that you are describing, and if it is the same one Chris is interested in, then the mangrove doesn't really do anything chemical, and would be of no help in a tank in this fashion. It sounds like all it is doing is providing a low flow swamp that turns anaerobic. Is that your impression?

[olgakurt]

mangroves leach some minor acids, but I don't think they have much affect. I think you are correct in that the mangroves mainly supply the organic matter which helps drive anaerobic conditions.

[chris_h]

I did a search and it appears they produce a lot of tannic acid.

I found several site that said they did.

Here are some:

http://terra.rice.edu/department/classes/geol516/belize_trip/mangroves.html second paragraph

this one says mangroves used to be used for their tannic acid to process animal hides into leather. http://www.life.uiuc.edu/plantbio/263/TANNINS.html

Read the last 3 paragraphs in this one. http://www.geocities.com/mseinstitute/mangrove.html

If you want more just do a search on yahoo for mangroves+tannic+acid, and you will find more sites than you want to read.

[MickAv8r]

Environment may play a role, being that most mangroves are in a low energy almost cesspool environment. As was stated about the decomposition of the leaves may also contribute to the water conditions.

Usually to utilze bark for tanning one must boil the bark to release the tannic acid which is obviously an active procedure and not going to occur natuarlly in a swamp.

I have a few mangroves in a refugium with extremely low flow rates and there has been no noticeable affect on the surrounding sand.

[chris_h]

I think the boiling is to make the acid into a form useable to humans. It would be very difficult to rub mangroves all over the animal hides. I think mangroves realese the acid without being boiled.

How large and old is your mangrove? Mabey to dissolve sand you need a mature mangrove with a large established root system that a small young mangrove would not have.


Is there a way to measure the ph of the bottom of sand beds without screwing stuff up? Mabey in my sump I could do an experiement and see if they really lower the ph of the sand.

[olgakurt]

For those with access to scientific journals (e.g. Elsevier), I found the following article that may shed some light on the topic. I haven't had a chance to read it yet.

"Tannin diagenesis in mangrove leaves from a tropical estuary: a novel molecular approach"

Geochimica et Cosmochimica Acta

Volume 65, Issue 18
15 September 2001
Pages 3109-3122