Elevated dissolved organic carbon and coral mortality.

[dtyharry]

Think we will have to agree to disagree on this one. You are saying that algae takes over when coral cover decreases, I am saying that increased algae levels cause the loss of coral cover, completely opposite. Increased overfishing lets the algae grow unchecked, and the resultant increase in dissolved organic carbon fuels the increase in microbes and pathogens which kill the corals. Pollution etc just adds to the problem of an already weakened ecosystem.
The reefs have been in decline ever since the colonial days but modern technology has made it ridiculously easy to remove huge numbers of fish from the seas.
Forgive my ignorance but I do not know what the numbers for the doc levels you posted are measured in.
I intend to try and contact forest lowher to get his input into this matter.
Correct me if I am wrong but the decline of the Caribbean reefs in the 80s was in a major part caused by a 99% collapse in the sea urchin population from a pathogen, which allowed the algaes to overrun the reef, combined with overfishing of the fish which may have kept it's levels in check.

[iggy]

Thanks for the reference to Lowher's work. I have not read it, but will likely get a copy.

Rapid declines in corals are often related to local temperature spikes, and eutrophic conditions due to river run off. If you really are concerned removal by GAC removal is very effective.

But I do not think DOC is an issue with ATS after running it a year. Excess low carbon-chain DOC WILL cause bleaching, so I would not discount his theory as well. I view this method much safer than vodka dosing. Evidence has shown some reef tanks to be an order of magnitude lower than natural reefs for bacterial populations, also indicating excess DOC is not an immediate concern for aquariums.

[SantaMonica]

An order of magnitude less sounds convincing to me. There is just not enough algal biomass in anyones tank to generate enough carbon to fuel enough bacterial growth faster than the corals can eat both the DOC and the bacteria.

Anyways, after reviewing chapter 8 again, I now remember what I was trying to think of: The nuclear testing on Christmas island. And although he discounts it's effects, I'd have to wonder how the DNA of the corals at Christmas were weakened by this. Also, if you look at the wind and water currents, they both travel from Christmas to Kingman, which is the same direction as the decreasing coral death:

http://www.oceanweather.com/data/ (Christmas is 1.5 degrees N, 157 degrees W)
http://www.jps.auckland.ac.nz/popup.php ... &action=pb

Further, he says that there is a 10X increase in microbes on Christmas. This is really not that much more; if you look at bacterial plots from reefs and open waters around the world, the amounts fluctuate greatly.

And as for his statement of pristine reefs having "almost no turf at all", I'd have to disagree. His "report" of this would be first I've ever heard of, in all the studies I've read. Reef faces, flats, and especially crests are the very place where turfs grow the best. As you progress down the slope, or towards the back reef, more fleshy types take over.

The main thing with any single study is, you need more numbers. He had 4 islands. We have 1000 scrubber tanks. He built a model and a hypothesis from it; we have actual results. He has wide fluctuating conditions, nuclear testing, and guesswork about decades-old conditions; we have controlled conditions, precise measurements, and hopefully no nuclear testing.

So even if his model/hypothesis is right (that's why I bought the book... to give it a chance), it only applies to real reefs.

[Floyd R Turbo]

we have controlled conditions, precise measurements, and hopefully no nuclear testing.

That is funny as hell man. I LOL'd for real.

[dtyharry]

I suppose it's a bit like the bible really, you can always find something in there that will justify whatever action you have just taken.
I seem to recall santa on many occasions saying how water changes are not needed because the water and nutrients on the reef are constantly being recycled. And then all of a sudden during a discussion about dissolved organic carbon comes eckman transport, that is the transfer of huge quantities of ocean water onto the reef. Is that not a water change? Seems you can find anything to fit if you want to.

[SantaMonica]

Yes I've said that, in relation to low-level inorganic nutrients which are limiting for most reef systems; these nutrients are grabbed immediately before they can get far. But DOC is the opposite; it's the largest component of the ocean, of the components that matter to reefs. I don't have quantitative numbers, but it's pretty well accepted that the amounts are big.

[iggy]

Your tank is yours. Not to be too obvious, but many successful tanks are hybrids of different defined systems.

I do partial water changes. I do them because I feed heavily and have mulm settle out on fast growing spongodis and in Reef Ready over flows. I also limit amount of feather dusters in sump. I do this for practical reasons, not for modeling a reef. I also use A LOT of 2 part mix. I judge my system on mortality and growth. I haven't lost anything fish or coral to anything other than corals growing too fast and touching in last 9 months.

On the other hand if you have a tang in a tank less than 180 gallons we will all call you on it. Just Kidding.

[dtyharry]

The dreaded tang police!

[dtyharry]

I emailed forest rohwer the author of the book I mentioned at the start of this thread. He replied very quickly and confirmed that the vast majority of evidence now points to excess algae growth causing the decline of the vast majority of the world's coral reefs. He is a renowned expert in his field and I am not going to argue with his conclusion.
He also said in relation to aquariums that the scrubbers appear to be so efficient at removing nutrients that the microbial growth you would expect does not occur and may be limited by other factors such as phosphate, unlikely, or iron, more of a possibility.

[Vannpytt]

Interesting.. So in terms he claims you could "overscrub"?

What about adding coral food? It was my understanding that it should counter the lack, and as long as the scrubber is cleaned weekly should not have too high levels of food in the system?