Originally posted by pwhitby
Hi Paul,
You originally corrected my use of the word data. You then said I misused the word bacteria.
No, I said you misused the word algaes...
So.........how do you get denitrification on all those tanks with no substrate. The rock has no animals. There is no substrate, yet we have denitrification.
I agree with you that surface films, on substrates like glass and sand will account for denitrification. In fact, they may do most of the denitrification.
You asked for the scientific proof of my statements. I gave you pictures of coral surface areas (which you still fail to acknowledge).
The rock is not - just - coral skeleton. In fact, coral skeleton may be a small component of most reef rock; that was really my point to Greg. Yes, your pictures are pretty. But, coral skeleton is an immediate substrate and gets colonized as soon as it is exposed. First, by bacteria - and then by algae and animals. In a short time it is largely covered and along with it all the initial porosity. My recollection is that the calcareous algal depositions are a lot less porous and may simply seal the coral porosity behind them.
Look at the rock in your tank, Paul, it is probably covered with coralline algae. I would bet you would be hard pressed to find any "fresh-looking" coral skeleton. I spent a bit of gazing into my tank this afternoon and while I can see a lot of surface irregularities, they are almost on "secondary" surface such as on coralline aglae or surfaces modified by animals.
I use a simple example to show how short a distance is required to establish anoxia. These are facts. I have shown you why I think my scenario works.
I will concede your scenario works - but with the following caveats.
1) Not much, if any original coral skeleton is present and exposed. So talking about coral skeletal prosity is really a starting point, and largely irrelevent. We/you need to address porosity of the rock not the skeleton.
2) I haven't the references I need here to argue with you further. The library at Montana State is pathetic on these subjects, and the nearest library where I could do work is at the U Wash, about 750 miles away. Bottom line, it ain't gonna get done. So...
3) I could take a look at the surfaces of some of these rocks with the local SEM, it is an excellent machine. Looking for surface porosity and bacteria would be kinda fun, but... it costs about $350/hour for non-faculty users and since I am not teaching now, I fall into that category. I can't afford it.
Bottom line, I will concede that you may be right. My understanding of the initial use of porosity - in 1990 or so - when the arguement was first posed - was that the people were discussing the pores in the rock created by the burrowing organisms. Not the pores in the rock made by coral formation, and I wrote the article in that mindset.
In your hypothesis, or supposition, animals move water through their burrows, and thus move solutes. Ok...so then what? What happens a few millimeters from the animals burrow? This is the basic fallacy of your argument.
I don't see any fallacy in the argument. The water is moved by the organisms into the rock, and bacteria lining the burrows as well as the animals, remove most of the oxygen as the water passes over the animals. The burrows are longer than the animals in them and this creates quite a good low oxygen environment behind and even surrounding the animals. Thus, the linings become the site of denitrification. In essence, as I see it, "your" biofilms are not on the surface of the rock but lining the burrows in it. That pumped water continues through the rock and exits either through some other burrow or through the cracks in the rock. Paul, these burrows are tightly packed, and in small rocks almost completely fill them. That the rocks have been burrowed out is what makes reef rock light, not the coral skeleton porosity. Much of the initial coral skeleton porosity is covered, filled in, or simply obliterated by the action of the subsequent occupying organisms. Then the rock becomes so much burrowing ground for the animals. Did you read the article? I mentioned the data collected and published by Kohn and Lloyd looking at rocks, and the number of worms in them; in many cases there were several burrowing worms per square centimeter, and these were not tiny worms. I was a student in that lab when they took apart those rocks. In good, really LIVE rock, the rock is honeycombed with the burrows. There are precious few areas where the rock is more than a millimeter or two from a burrow. Additionally, in such rocks the surface of the rock doesn't have a thin boundary layer of almost stagnant water over it, the action of the animals moving in, out, and around the rock disturbs and, in fact, destroys the boundary layer.
So... this rock is not fresh coral skeleton. It is highly altered material which has been actively excavated by burrowing organisms. Frankly, I think the original coral skeletal porosity is probably irrelevent.
In any case, as I said, I am willing to concede that with our "dead" once-live rock your scenario may work and may be the major site of denitrification. Presently, although I am not convinced, I can't get either the data or the references I need to resolve this. I would like to see some indication from aquarium data that it does work, but those data will be lacking too, I guess.
I think your scenario is at least a potential reasonable explanation some of the denitrification we see in our systems, and as such I would request that you, and Tim, if he wants, write up an article for submission and potential publication in Reefkeeping. I would recuse myself from the editorial process if you like. You would be paid for the article, and you probably have spent more time arguing with me than it would take to write a decent article of about 3000 words. This would be a nice way to recover some of your losses.
