[Coral-List] [SPAM] Re: coral bleaching: response to Goreau
delbeek at waquarium.org
Thu Jun 1 17:07:53 EDT 2006
There are a couple of points in this discussion that I feel the need
1) Shops selling phytoplankton as coral food - most research that I
have read involving feeding in stony corals deals mainly with the
ingestion of ZOOplankton. Soft corals, particularly azooxanthellate
ones such as Dendronephthya have been shown to feed on phytoplankton.
This makes sense to me since most of these corals lack nematocysts
and their polyp structures appear to be more suited for sieving food
from passing water than stinging and capturing it as can be seen in
stony corals which all seem to have nematocysts ... why sting a
phytoplankton cell to capture it which is basically a passive entity
unlike a struggling copepod?
I have a pet theory that people who report responses from corals when
fed phytoplankton could be seeing the result of any number of factors
such as the addition of nutrients, the decay of phytoplankton leading
to increased nitrogen and phosphorous levels, to the increase in
filter feeders and hence, an increase in reproduction of these i.e.
more zooplankton being generated.
2) Feeding vs. non-feeding of corals in captivity - yes corals will
feed on zooplankton and more meaty food in the case of corals with
polyps large enough to take them. No one disputes this. What is in
question is do corals in captivity need this? Given that nitrogen,
phosphorous and organic nutrient levels are generally several times
that found on natural reefs is this enough to keep the corals
"happy"? The success of aquarists in Europe with stony and soft
corals in the 1970s and 1980s, without any feeding, would tend to
support this idea.
3) The role of dissolved nutrients - The Waikiki Aquarium has been
keeping, propagating and spawning stony corals, mainly Acropora,
Montipora etc since the late 1970s. We have never added any sort of
zooplankton or phytoplankton to our systems. We use a saltwater well
as a water source for the majority of our exhibit and they are
semi-open systems. The well is 80ft down in coral rock, the chemistry
of this water has been discussed in Atkinson et al. 1995, there is no
zooplankton or phytoplankton in this water. That is not to say that
there isn't any bacteria in the water, or that there could be
plankton being generated in the systems themselves. All I can say
with absolute certainty is that WE do not feed the corals. Yet, we
have observed the release of eggs, sperm and egg/sperm bundles in
corals such as Acropora, Sandalolitha, Montipora, Euphyllia and
Goniopora. What our water IS rich in is nitrogen, phoshporous, iron,
managense, carbon dioxide etc. ... so my feeling is that the
zooxanthellae and perhaps the coral tissue itself, is getting more
than enough of what they need from the water.
4) Increasing contact with the aquarium community - there is an
annual conference in North America called The Marine Aquarium
Conference of North America (MACNA), this year it will be held the
weekend of Sept 23rd in Houston, Texas. This annual conference is the
best place to meet with and observe what hobbyists are doing. There
have been several marine scientists who have spoken at this
conference such as Giselle Mueller-Parker, Daphne Fautin, Marlin
Atkinson, Charlie Veron, Robert Myers, Bob Richmond, Cindy Hunter ...
to name just a few. While there is some contact with hobbyists by the
scientific community there is certainly room for much more. I think
this sort of interaction will only increase for the simple fact that
many of the up and coming marine scientists today have started off by
keeping reef tanks as a hobby, and I am in fact seeing this already.
There are of course other such conferences in Europe held in Germany,
France, Belgium and The Netherlands. Next April there will be a
conference in The Netherlands dealing specifically with the captive
husbandry of corals in public aquariums, of which I am a member of
the steering committee ... we would dearly love to have a strong
representation from the scientific community especially in the field
of coral nutrition, effects of UV, coral colouration, coral
reproduction, etc etc. The days of marine scientists claiming it was
impossible to keep live coral while hobbyists in Europe and elsewhere
were already doing so, are thankfully behind us for the most part.
Finally, I think one needs to be cautious about making sweeping
generalizations about what corals need or don't need in terms of
feeding when it is becoming increasingly obvious that the corals have
various abilities to gather, use and process sources of nutrition
spread across the genera.
J. Charles Delbeek M.Sc.
Aquarium Biologist III
University of Hawaii
2777 Kalakaua Ave.
Honolulu, HI, USA 96815
808-923-9741 ext. 0 VOICE
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