[Mat]

Qualcosa su cui meditare

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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. ... 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