[Coral-List] [SPAM] Re: coral bleaching: response to Goreau

[Charles Delbeek]

There are a couple of points in this discussion that I feel the need 
to address:

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.

Aloha!


J. Charles Delbeek M.Sc.

Aquarium Biologist III
Waikiki Aquarium,
University of Hawaii
2777 Kalakaua Ave.
Honolulu, HI, USA 96815
www.waquarium.org

808-923-9741 ext. 0 VOICE
808-923-1771 FAX