Science - March 17, 2005

Aquarium coral is not always healthy

Coral is becoming increasingly popular as an exhibit in zoos. But this fascinating organism is not always kept in the best of conditions behind glass. Wageningen fish experts are coming to the aid of public aquariums, together with colleagues from Germany, Israel and Italy.

‘The coral on display for the public does not always look very attractive, and they often do not grow well,’ says Dr Ronald Osinga, project leader of the European project Coralzoo, that starts this year in May. The aim of the project is to compile good protocols for growing and maintaining hard corals in aquariums. These are the corals that form reefs.

What is it that aquariums are doing wrong? Osinga, who will take up a postdoc position in the Fish Culture and Fisheries group, points out a few possible problems: ‘Insufficient light and food are the main problems. Only making light available is not enough for growing coral, and many corals consume plankton much more actively than was previously assumed. In addition, the quality of the light is also important; it is very difficult to imitate sunlight in large public aquariums.’

The mineral composition of the water is also a matter of concern. The concentrations of calcium are often too low, whereas coral requires this to build. ‘Water quality problems are also the result of the imbalance in the biochemical processes in aquariums. There are far more animals per litre of water in an aquarium than in the sea. This leads to big fluctuations in nutrients and waste products, are corals are very sensitive to these changes.’

The Wageningen sub-department of Food and Bio-process Engineering and the Fish Culture and Fisheries group will collaborate with the public aquariums in Burgers Zoo and Blijdorp Zoo in the Netherlands, and with zoos in other European countries. Given the threatened position of marine coral reefs it is important to be able to reproduce corals in captivity so that the genetic diversity of corals can be preserved. / HB

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