Coral life as probed by their fluorescence emission

Abstract

The fast fluorescence rise O-J-I-P (Strasser et al. 1995; Strasser and Strasser 1995) was used to monitor coral health trough the photosynthetic activity of their zooxanthellae. The advantage is that such type of measurements are non invasive and the sample is exposed to the experimental light only during a few seconds. We have provided coral with "quasi-natural" conditions : a sea water aquarium of 60 l with the polyps living on rocks close to the glass wall of the container. The temperature and salinity were kept constant, illumination was provided with three 18W reef aquarium neon, and one 18W blue neon lamps. Chlorophyll fluorescence was induced for 10 to 20 seconds every hour with a PEA-Instrument (Plant Efficiency Analyser built by Hansatech Instruments King¿s Lynn Norfolk, PE 30 4 NE, GB) during several months. Different species of Anthozoa are being studied. Two species of Actinodiscus, and one unidentified (probably Madracis) freshly collected from Bali (Indonesia) and St Lucia (Lesser Antilles) respectively. The signals are analysed according to the JIP-test. Most expressions show typical circadian rhythm. The extrema of the observed oscillations do not coincide with the moment when the ambient light of the aquarium was turned on or off. Long term experiments with light cycles will be reported.