Dustin L. Laurence
laurence at alice.wonderland.caltech.edu
Fri Oct 11 16:34:50 EDT 1996
>Anecdotal reports of maximum acceptable temperatures vary considerably.
>I normally avoid temperatures above 26 C, but believe I'm acting
If you are interested in amateur anecdotes, I have one, if not, feel
free to ignore this and I'll return to lurking.
I'd say you are acting extremely conservatively, if you can control
the temperature with reasonable accuracy. This summer we have been
running around 27C--this would have been a bit higher, perhaps 28C,
but the temperature was adjusted low following a bleaching episode
which I will describe. I have not dialed the temperature up since
then because I have not been here to observe the tank continuously. We
see better growth as temperatures increase, even up to within a degree
or so of what we regard as maximum (and it's cheaper to run the chiller
too, a useful bonus on a rather limited budget).
Common wisdom among advanced amateurs is to expect bleaching around 29
or 30C, which is what we observed. Early this summer a thermometer
failed, reading about 2 degrees low, and our tank was running around
30C instead of an intended 28C. This persisted for perhaps three weeks,
since lighting was changed to higher Kelvin-rated metal halides around
the same time and I was looking at possible UV-induced bleaching instead
of temperature (and since the temperature read OK). I think the
lighting was a contributing factor, at least as a trigger, but I don't
think it could have happened without the elevated temperature.
After about a week of these elevated temperatures we began to notice
bleaching. The hardest hit were small fragments. We lost two fragments
of Seratiopora hystrix (I'm spelling these things from memory, and these
are amateur NOT professional ids so beware) which had also been recently
shipped, one unidentified Acropora fragment, and probably a couple of
other that have slipped my mind. A larger Stylophora pistilata fragment
bleached completely but survived azooxanthellate for a month or two
before dying. I feel particularly bad about this specimen because if I
had been here enough I think I would have had a good chance of saving it
by feeding it in that critical month.
Another unidentified Acropora sp. fragment from the same parent colony as
the dead one just mentioned bleached but did not show tissue loss and has
made a complete recovery, and a third partially bleached but survived car
transport from Los Angeles to Sacramento and has reportedly also completely
recovered. A fourth, the largest, did not bleach and was also transported.
Two unidentified Acropora sp. fragments from a different parent (of a
different species) which were fragmented at the same time as the earlier
four also did not bleach and easily survived transport. Both parent
colonies showed no obvious signs of stress.
An Acropora humilis suffered total bleaching but only about 50% of the
tissue subsequently died--it has since completely recovered its symbionts
on the remaining tissue and is doing well. A Millepora sp. suffered maybe
90% tissue loss--I believe there is a small amount of still living tissue
still but I doubt it can recover.
The larger and better established Acropora and the other non-Acroporids
were not noticably affected. In addition to the two parent colonies
mentioned above, another small Acropora colony and an Acropora fragment
(both unidentified) survived without problems, as did two sibling Pavona
cactus fragments, a Porites cylindrica, and a Montipora digitata.
There were only two large polyped corals in the tank at the time, both
Catalyphilia. The larger and long-established one was damaged, but I
think would have survived if I had been here to keep an eye on it and
if it had not been subsequently heavily harassed by a Z. veliferum tang.
This coral was on the extreme opposite end from the halide fixture that
was upgraded and should have received very little from that light, so I
think this must have been a purely temperature effect. A small
Catalyphilia that would have received some light from the upgraded bulb
>I'd appreciate receiving actual observed critical temperatures from
>various parts of the world.
It would also be interesting to me to know if the critical temperature
is significantly different in captivity.
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