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CORAL PHOTOBIOLOGY STUDIED WITH A NEW IMAGING PULSE AMPLITUDE MODULATED FLUOROMETER1
Article first published online: 28 FEB 2005
Journal of Phycology
Volume 41, Issue 2, pages 335–342, April 2005
How to Cite
Ralph, P. J., Schreiber, U., Gademann, R., Kühl, M. and Larkum, A. W. D. (2005), CORAL PHOTOBIOLOGY STUDIED WITH A NEW IMAGING PULSE AMPLITUDE MODULATED FLUOROMETER. Journal of Phycology, 41: 335–342. doi: 10.1111/j.1529-8817.2005.04034.x
1Received 19 March 2004. Accepted 22 June 2004.
- Issue published online: 8 MAR 2005
- Article first published online: 28 FEB 2005
A new high-resolution imaging fluorometer (Imaging-PAM) was used to identify heterogeneity of photosynthetic activity across the surface of corals. Three species were examined: Acropora nobilis Dana (branching), Goniastrea australiensis Edwards & Haime (massive), and Pavona decussata Dana (plate). Images of fluorescence parameters (F, Fm′, effective quantum yield, optimal quantum yield, electron transport rate, relative photosynthetic rate, and non-photochemical quenching) allowed heterogeneity to be detected in terms of position on colony and indicated that the photosynthetic activity of polyp and coenosarc tissues responded differently to changing light for all three species. The Imaging-PAM offers a special routine, with which images of PAR absorption (absorptivity) are obtained. In this way, for the first time it has become possible to derive images of the relative photosynthesis rate. Polyps had a lower PAR absorptivity than coenosarc tissue for A. nobilis and P. decussata, whereas G. australiensis showed the opposite pattern. Acropora nobilis showed heterogeneity along the longitudinal axis of the branch, which could be differentiated from the effect of variations in illumination across the rugose and curved surface. Diel changes were apparent and influenced the longitudinal heterogeneity along the A. nobilis branch. Images were also obtained showing the degree of photoinhibition caused by high-light stress across a coral surface at a hitherto unobtainable level of resolution.