The Role of DOC in Coral Death

[Timfish]

Stumbled across this video and it struck me as a pretty good introduction to the role DOC, Dissolved Organic Carbon, plays in the death of corals:

Forest Rohwer's "Coral Reefs in the Microbial Seas" goes into more detail and has plenty of references for those so inclined to read more. The kindle version is available for only $10

[Gig 'em @ NDstructible]

So what I'm hearing is increased carbon in the tank will lead to coral death due to biofilms growing on the coral. I feel like dosing vodka and using biopellets would directly cause coral death because you're introducing more carbon into the tank. Right?

[FarmerTy]

I think it's a little more complicated than that. They were demonstrating that carbon was the limiting factor in bacterial growth and then went on to explain the compounding issues of high carbon leading to higher bacterial growth...macro algae growth..etc... then how that issue compounds and feeds itself to kill off coral reefs.

For carbon dosing in a tank, we're dealing with a much different environment. What applies in the ocean, doesn't always translate to our little boxes of water and electricity.

For carbon dosing in a reef tank, the bacteria cultured is actually removed if done properly. Most will tie their biopellet reactor output directly to the skimmer to export bacteria produced and never let it into the tank system. For liquid carbon dosing, that's a little harder to do since it's dosed into the tank system itself and not contained in a reactor. Either way, carbon dosing is always paired with aggressive skimming so most of the bacteria created will be removed... ideally exporting the nutrients with them.

[Viet'spride70]

+1 well said Ty.

beside that u r I.A.W, u do have very well knowledge about carbon dosing Ty....shall I say Genuinely I.A.W?

[FarmerTy]

Oh, I'm genuinely weird as most that know me can attest to. I think I live in the right town for it though.

[Viet'spride70]

[Gig 'em @ NDstructible]

Yeah I was definitely over simplifying. I guess I feel like pointing out that one of the primary building blocks of life (carbon) for the fastest replicating life form (bacteria) is a limiting factor for its growth is a given. If you spike a system with nitrogen or phosphorus, but don't have carbon you won't get any growth, but you'll still poison your system because they are toxic at high concentrations and convert into toxic constituents. So saying having more carbon in a system directly causes death seems too simple to me.

Could it be that with more building blocks for life, the fastest and most aggressive life forms in the ecosystem will thrive and begin stripping the water of other minerals and nutrients that aren't as readily available? Trace nutrients and minerals that are necessary for life are suddenly missinf because they have now become immobilized in these aggressive growing species. Now the corals are starved of something else as a result. And also it is known that bacteria and other micro organisms are continuously battling each other for space and resources and begin to create toxins when their populations grow too large. Could it also be that when an influx of building blocks for life causes a population boom, the species of bacteria begin to overpopulate, which then triggers the production of population controlling toxins and organic compounds that not only poison the bacteria and other microorganisms around it, but also the coral as a consequence?

I guess what I'm trying to communicate is that he is right that more carbon will result in coral death, but what I want to hear is more "why" carbon causes death. He said more carbon going to the coral will result in increased coral mucus microbes, which leads to death. But I have spot fed my corals for months before giving them copious amounts of carbon and they thrived in those instances. The Increased nutrients to the coral and the corresponding mucus microbes did not lead to death. It's not just the fact that the coral is getting more carbon that causes death from mucus microbes, but maybe some other factors like disappearing micronutrients or overpopulation of microorganisms that lead to death.

Sorry, I totally skipped the "what" and dove straight into the "why" with the video. Take my thoughts as an over analyzing rant as I sit bored in a truck in a field in NE Texas ?

[Viet'spride70]

I am no Chem tech but here what I think :

When over dosing carbon, which increases bacteria population to a certain limit, they strip out all nutrients below the zero or whatever. Corals get stress, mostly look pale, they release their Toxin to defend which in some way benefits to bacterias and they got bacteria infestation. ....

Or maybe I didn't get enough sleep in last couple days.

[Timfish]

Like I said this is just an intro video and it doesn't even touch on the roles sponges play in converting DOC to DIC. DOC is a very complex subject with many thousands of compounds and is key to causing a shift in the microbial populations in the coral's mucus coating with increasing pathogenic species and a decrease in the beneficial species that help a coral protect itself and to help it recycle nutrients and utilize nutirents (some convert nitrogen to nitrates, for more info search "Coral Holobiont"). (If you chase down research papers on mucus, that in itself is a very complex subject with the products from the symbiotic Symbodinium spp. dinoflagellates being a major component.) It would be nice to say this only happens in the wild but much of the research is being done on corals in aquaria which is corroborating what's being seen on reefs.