"Natural" Reef Temps Can Increase the Spread of RT

[jamesw]

I'm not sure if everyone caught this article in the last issue of Advanced Aquarist:

http://www.advancedaquarist.com/issues/ ... /media.htm

A recent paper in the Journal of Marine Biology discusses a new pathogenic bacteria V. coralyticus which causes what looks to me like RTN.

To quote from Charles Delbeek's media review:

In this paper Ben-Haim and Rosenberg describe how they were able to isolate a previously unknown pathogenic bacterium Vibrio coralyticus YB from colonies of Pocillopora damicornis collected from the coast of Zanzibar (in fact they found 15 strains of Vibrionaceae that were dominant in diseased colonies but not healthy ones, but V. coralyticus YB was the most virulent). They were able to inoculate healthy colonies with this bacterium (by adding it to the water and by putting an affected coral into direct contact with a healthy piece) and produce the same symptoms of rapid tissue loss resulting in death within a few weeks. They were also able to infect other colonies of P. damicornis collected from the Red Sea (ambient water temperature of collection area was 22-26°C) with the same bacterium.

And more importantly:

In experiments of disease transmission at differing temperatures it was found that no symptoms appeared after inoculation at 20 and 25°C after 20 days (68-77°F), but that 100% of the tested fragments showed disease and died at 27 and 29°C (80.6-84.2°F) after just 16 days (the rate was slightly faster at 29°C than 27°C).

When the pathogen was introduced into aquariums with a temperature of 80.6 to 84.2 ALL OF THE CORALS DIED!

Thoughts?

Cheers
James Wiseman

 

[Anonymous]

Interesting - but how prevalent is RTN these days? My head has been down in the sump lately :mrgreen: but I haven't seen anyone really complain about it happening to them? Seems like with the emphasis on captive raised SPS corals that the risk of such a pathogen is quite low.

Unless someone running a chop shop imports a wild colony and infects a bunch of frags before shipping them across the country - even then the aggressiveness of this pathogen seems to indicate that it won't exist very long.

Seems to me that those at highest risk i.e. large SPS tanks and adding wild colonies may do well to heed the advice and drop tank temp to 76-77 degrees for a 2-3 week quarentine stage when adding such animals.

But in all reality I haven't heard much about RTN, I mean real unexplained RTN, plenty of accounts of tanks crashing after power outages or other such problems.

 

[john f]

I have a few colonies right now showing RTN like symptoms.
So I know for sure RTN is sill around these days.

My take on that paper is "DUH!" Any virulent bacterium will produce symptoms in a shorter timeframe hen kept at a higher temp (within its growth limits)

I have not read the entire article so I don't know how long they tested for RTN symptoms. As far as I can tell, they did not show the bacteria to be non-pathogenic at the lower temp.................just non-pathogenic within the 20 day timeframe. Move that timeframe out to 60 days and lets see what happens.
I may be the bacteria is non-pathogenic at the lower temps, but they need to prove that.
Also, keep in mind Charles is a proponent of lower reef temps, so he would look for papers to support his views when writing an article.

Maybe Dr. Ron can counter with some papers of his own?



John

 

[JeremyR]

I would read the entire article john, I think it's interesting at the least. I'm not advocating anything, so don't flame me... but it was mentioned that at least one strain of vibrio in another coral disease study was unable to infect said coral below a certain temp as well...

I remember how alot of us made fun of craig bingman's earlier vibrio theory... makes you wonder now eh?

 

[john f]

Why would you think I would flame you?

BTW,
I followed the Bingam recs and have treated several colonies of acros in the past with chloramphenicol.
I worked sometimes and sometimes did nothing.
So my opinion is if it was something as simple as a vibrio bacteria causing RTN the chloramphenicol would work all the time. Regardless of temps.


John

 

[JeremyR]

I meant I didn't want people in general to flame before thinking it thru.

Problem with RTN is that I think there are prolly different causes.. when thin tissue corals like acro die, they can go pretty fast and it gets labeled RTN. That doesn't mean that this paper is off in this instance or that people should ignore what the article is saying. I see it as another interesting tidbit to file away for awhile and stew on rather than making a quick judgement on temp yay or nay.

 

[dizzy]

Recent articles I have read seem to be making the case that cooler temperatures provide less opportunity for diseases organisms in coral than warmer temps. This would also lend credibility to the theory that warmer than normal temps caused massive bleaching incidents a few years ago. If growth slows at cooler temps, but the corals stay healthier it is an acceptable tradeoff IMO.

I just wanted to make a point about RTN. A few years ago I attended a Western Conference at which Paul Hogue (possible mispelling) from the Great Barrier Reef Aquarium in Townsville, Australia was speaking. Paul showed a video in which they were able to initiate RTN like symptoms at GBRA by placing a colony of acropora in seawater and slowly diluting the tank water it was in. His point and one that would still apply today is that RTN, or the rapid death of corals can be the result of stress or improper conditions. RTN is a like popeye in fish, in that it is an indicater that something is wrong, but not an actual disease in and of itself.

 

[saltshop]

A recent paper in the Journal of Marine Biology discusses a new pathogenic bacteria V. coralyticus which causes what looks to me like RTN.

Hi James,
Please note that what was found in the work by Rosenberg was NOT RTN, but temperature induced bleaching caused by the bacteria and eventual death of the coral over a 16 day period. It was not the typical sloughing off of tissue with intact zooxanthelae that is what is known as Shut-Down Reaction (SDR), Rapid Wasting (RW), Rapid- or Stress-Related Tissue Necrosis (RTN/SrTN), White Plague (WP), or White Death (WD). (Geez can we possibly get more names for the same problem? ) Also V. Coralyticus has only been associated with Pocillopora at a certain location. It is quite possible that this bacteria is only associated with this genus/species of coral. For instance, it is an entirely different strain of bacteria that causes bleaching in Rosenberg's original work with bleaching Oculina in the Med. Sea. These bacteria are also almost impossible to culture outside of their host so it is possible that each genus of coral could have a different species of bacteria that causes bleaching...crazy world. While the appearance look similar the time frames for what was found here and what is known as RTN are completely different. It could point to bacteria possibly playing a role in RTN be it the primary or secondary cause though..hard to say really.

I was actually reading a review of some coral diseases this evening so this thread caught my eye and thought this quote might be of some interest. It is from Dr. Antonius at the University of Vienna regarding SDR/RTN etc.

Observations in laboratory experiment and field observations of corals under sublethal (abiotic) stress such as elevated temperature, sedimentation, chemical pollution, have revealed that specimans can die from a simple scratch. Such sudden disintegration of the coral tissue, which starts at the margins of the injury, is characterized by sloughing off the tissue in thick strands of blobs from the coenosarc, leaving behind a completely denuded coral skeleton. From the initial interface, the phenomenon proceeds in an enlarging circle on massive corals, or moves along branches in ramose forms, spreading to all-branches upon reaching a junction. It is still unclear if SDR represents a disease on its own, as the triggers match those in White Band Disease or White Syndromes, although there seem to be significant differences regarding the speed this disease affects a colony. Thus, SDR is especially dangerous as it can spread with an average speed of 10 cm/hour--fast enough to be visually observed! Being contagious, SDR can be transmitted by a floating strand of dissolved, contaminated tissue to produce an onset on a neighboring stressed colony. Thus triggering a catastrophic chain reaction, which may occur several times during the course of a season.

The part that is so interesting is that you start with what appears to be a normal coral, put it under stress that is not biological, scratch the tissue and you get a reaction where the coral is rapidly consumed by "something". It is almost like all of the bacteria, fungii, cilliates, and protozoans that 10 minutes ago where part of the corals normal surface fauna are now allowed to consume the tissue and cause it to slough off. The "contaminated tissue" as he puts it, then proceeds to cause a chain reaction in other previously uninfected corals (typical RTN scenerio) so it makes me wonder if something triggers a virulence gene in "something" just like a 1-2C increase does in the case of Oculina and its Vibrio. I think eventually someone will figure this whole thing out, but we probably have a while to wait. Rosenberg's work is definitely a start though.

 

[jamesw]

Interesting JB!

I tried responding to this thread last night but my machine crashed in the middle of a lengthy reply!!! argh!

What I think is especially good about the Roserberg study is that it was carried out in aquariums.

For years we have heard that in nature corals are healthiest at their natural reef temperatures - makes sense since those same corals evolved to fit that niche.

But then along comes data that shows that in an "un-natural" setting such as an aquarium - these same "natural" reef temperatures can increase the growth rate and virulence of disease.

Seems like more data to suggest that while we should strive to replicate a coral reef to the best of our ability in our small glass boxes - we need to be aware that aquariums are NOT natural and we need to be aware of their inherent constraints when we manage them.

Cheers
James Wiseman