Nitrate uptake by the coral Diploria strigosa

[Mr. Fosi]

I just finished reading a very cool paper that was recently published in Marine Biology.

 

"Nitrate uptake by the reef coral Diploria strigosa: effects of concentration, water flow, and irrandiance" PDF file, 381.7 KB

 

Too bad Diploria strigosa isn't a coral that most people would choose to keep in their tanks, but there is mention made of the NO3 uptake rates of 3+ species of acropora.

 

Once of the reasons that I like this paper, is that there was some discussion of why it is important to keep the water flow up and turbulent around corals, specifically stony corals (bolding added by me):

 

"Increased water flow can increase uptake of

dissolved gases, ammonium and phosphate

by various corals. At low flow, uptake of any dissolved

substance causes localized depletion in the water

immediately surrounding a coral, creating a diffusional

boundary layer. Increasing water flow causes this

boundary layer to thin or breakdown and delivers

increased amounts of dissolved nutrients and gases to

the coral surface (termed mass transfer), thereby

increasing uptake."

 

"In the experimental chambers, nitrate uptake rate was

positively correlated with water flow... up to the

maximum flow speed examined..."

 

"... oscillatory flow prevents

the buildup of a stable benthic boundary layer and provides

much greater shear, and thus momentum transfer,

through the water column near the reef substrate.

The potential for mass transfer, from the

water to coral tissues, for example, is thus greater at sites

with strong wave effects or increased turbulence."

 

 

There were a couple other interesting tidbits offered up, such as:

 

"There was no significant effect of light intensity on

uptake rates at any concentration. Furthermore,

time of day did not affect the nitrate uptake by

D. Strigosa... The absence of light effects on nitrate

uptake by D. strigosa agrees with studies using other

corals found several coral species to require

unnaturally long periods of darkness before nitrate

uptake rates were reduced."

 

 

And one that it unfortunate for me, because it is very likely the species of Madracis that I have in my tank:

 

"The only coral then that appears

incapable of nitrate uptake is M. mirabilis, which

even after 1 month exposure to nitrate in the absence of

ammonium did not assimilate NO3. An inability to take

up nitrate has also been reported for other

cnidarian–algal symbioses, such as medusae and

sea anemones."

 

 

I am no expert, but I found this paper it be fairly well thought out and executed.

 

Definately an entertaining read.

 

Thoughts?

[jeremai]

So, it explained what we've known all along? Cool.

 

I've only been diving in Bermuda twice, but the only place I saw Diploria was in the rubble zones on the outer borders of seagrass beds - the coral dominates. But if they say it's found in all zones, I believe them... it was probably there and I didn't see it.

 

Mr. Fosi, why wouldn't people choose Diploria spp. for their tanks? They are amazing to look at - especially D. labyrinthiformis. I wonder why it's not commonly availble? It's definitely not hard to find in the wild. I don't know the growth rates, but I'm sure it could be fragged to managable sizes, like most other labrynthine corals...

[RayWhisperer]

I'm pretty sure I've got a Diploria sp coral. I don't know what species, but near as I can tell it's Diploria. Very hardy, beutiful coral IMO. Mine is purple and teal, purple on the ridges and teal in the valleys.

[jeremai]

Is it helping with nitrate control?

[Mr. Fosi]

So, it explained what we've known all along?

 

I guess it really struck me because I see many so-called experts doling out advice about corals and always harping on brisk, turbulent flow.

 

I'm the kind of guy that doesn't believe just-so stories until he sees some data supporting them. That's why I found it so interesting.

 

Mr. Fosi, why wouldn't people choose Diploria spp. for their tanks?

 

The pictures that I found online were of corals that looks mostly brown or tan, even when the photographer used a strobe. I thought most people don't choose brown corals for their tanks...

 

I'm pretty sure I've got a Diploria sp coral. I don't know what species, but near as I can tell it's Diploria. Very hardy, beutiful coral IMO. Mine is purple and teal, purple on the ridges and teal in the valleys.

 

Sounds way cool, do you have any pics?

[RayWhisperer]

I can't post pics, I think it's due to size... I don't have any software to resize the pics. And no, I won't use Photobucket!!!!!

 

PM me your email addy. They come through kinda crappy, but good enough to see the color and what it is.

 

Oh, J, to answer your question... I really don't know, my nitrates are almost always undetectable.

[jeremai]

I guess it really struck me because I see many so-called experts doling out advice about corals and always harping on brisk, turbulent flow.

 

I'm the kind of guy that doesn't believe just-so stories until he sees some data supporting them. That's why I found it so interesting.

Fair enough.

 

The pictures that I found online were of corals that looks mostly brown or tan, even when the photographer used a strobe. I thought most people don't choose brown corals for their tanks...

Most appear yellow or bluish in the wild, at least to me - I'm sure they would look even more amazing under specialized aquarium lighting. Even if the color is a touch drab, though, their form more than make up for it.

[Mr. Fosi]

Pics came through. It does look a lot like a Diplora sp.

 

I resized them and have posted them here (I hope you don't mind).

 

 

 

 

 

 

FYI Ray: Here is a great little program that I have used for years. It is freeware and I use it to resize and color correct images all the time. I like it because it is small and doesn't copy pieces of itself all over your machine. IrfanView

[MrAnderson]

Xenia sp. also eat nitrates.

 

http://www.nano-reef.com/forums/index.php?showtopic=59051

[Mr. Fosi]

Anderson! I was hoping you'd show up.

 

What did you think of the paper?

[jeremai]

Ray, that Diploria is awesome. Where did you get it? This could be the 'next big thing', hehe.

[RayWhisperer]

Thanks, I picked it up at my favorite LFS. I think it was $63, so not too bad considering it's color.

[jeremai]

Well, it would be a shame to alter that genus-specific mound shape, but if it gets to big and you need to frag it, you know where to find me.

[RayWhisperer]

UTR wanted a frag too. Sorry, I would not want to destroy the shape.

[jeremai]

Understandable. Guess I gotta find my own, hehe.

 

Sorry for the derailment, Mr. Fosi.

[RayWhisperer]

Oh, J, to answer your question... I really don't know, my nitrates are almost always undetectable.

I was just thinking(yeah, big suprise! I can think). I've had this coral for about a year, it has put on about 1/3 " all the way around the base. Now I realize these are slow growing corals, I just don't know how slow. Dose this seem like a normal growth rate????? Perhaps if I let the nitrates creep up a bit(5-10 PPM range) it would grow quicker???? What do you guys think?

[jeremai]

I was just rereading the paper for notes on growth rates - but, that (unfortunately) was not the focus of the experiment.

 

And, since this coral is relatively absent from the hobby, there's not a lot of general information out there - perhaps someone with search capabilities over at RC could have a go, but my Google search of the site yielded nothing of importance.

 

Shame. They're so garsh darn purty!

 

edit: This site says 5mm per year. Wanna take their word for it?

[MrAnderson]

Looked like a pretty solid paper. Very technical.. and I liked the experimental design. It asked really simple questions with simple answers which is good, the data were very clear.

 

I looked but couldn't find anything in the discussion section about mechanisms for nitrate consumption. In the paper in that link I posted they speculate it goes to "protein production" which is certainly likely, but HOW would be really interesting...

 

Also, the authors mention multiple times that it seems that the norm for stony coral species is to take up nitrates, with only a few exceptions. Kinda cool.

[travisurfer]

nice article. im planning on xenia to get rid of my momentarily nonexistent nitrates.

[Mini_GBR]

I'd love one of these, does it have to be on the sand, or can it be placed anywhere?

[RayWhisperer]

I'd love one of these, does it have to be on the sand, or can it be placed anywhere?

Jeremai brough it to my attention that Diploria sp. are protected and cannot be harvested. So, as this new info has come to light, I'm thinkng mine is something other than Diploria.

 

As for it's care, I'd imagine the sand bed would be the ideal placement. I can't see why putting it on the rock would be of any harm to it though. If you can get a "Maze Brain" I'd highly reccomend it. They are very hardy and interesting additions to the reef environment.

[Nuhtty]

nice article. im planning on xenia to get rid of my momentarily nonexistent nitrates.

 

 

My beginning days of the xenia refugium

 

 

 

 

[Gill Snork]

Interesting paper Mr. Fosi. It reads like one of my mass-transfer textbooks except I can follow it.

 

One point I think would be worth examining:

 

If you must increase the flow rate (actually just the velocity near the corals) in order to diminish the boundary layer, by applying mass transfer principles, you could just increase the concentration and lower the velocity and still achieve the same results since the boundary layer would increase, but the concentration gradient would increase as well, effectively simulating the same results and mass transfer rate.

 

So, in theory, you could regulate your nitrates by simply changing the flow (velocity) of the water past the corals. If your nitrates increase, increase the flow and you will increase the nitrate transfer. And then you could dial it back once they lower to acceptable levels. With some fine tuning, you could achieve a flow rate that would keep nitrate levels fairly constant (assuming everything else was somewhat constant as well).

 

 

Just a point to ponder.

 

Gill

[Mr. Fosi]

Intersting point Gill.

 

It is a neat thing to consider, but since NO3 levels are in a constant state of flux in an aquarium, you'd need some sort of feedback inhibition system that would react to NO3 concentrations in real time.

 

I am happy to have found an article that was published in a peer-reviewed journal (and doesn't have Eric Borneman's name on it) that confirms the conventional wisdom of the marine aquarium "experts".

 

I think it is important to constantly fact-check the information that is relayed to us by our peers and by people who are regarded to be experts in our hobby. Afterall, reliable information that includes an explanation of its origin is a boon to everyone.

[Gill Snork]

Well put.

 

I agree.