Photobiology of endolithic microorganisms in living coral skeletons: 1. Pigmentation, spectral reflectance and variable chlorophyll fluorescence analysis of endoliths in the massive corals Cyphastrea serailia, Porites lutea and Goniastrea australensis |
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Authors: | P J Ralph A W D Larkum and M Kühl |
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Institution: | (1) Institute for Water and Environmental Resource Management, Department of Environmental Sciences, University of Technology, Sydney, Broadway, 2007 Sydney, NSW, Australia;(2) School of Biological Sciences, University of Sydney, 2006 Sydney, NSW, Australia;(3) Marine Biological Laboratory, Institute of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsing?r, Denmark |
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Abstract: | We used microscopy, reflectance spectroscopy, pigment analysis, and photosynthesis-irradiance curves measured with variable
fluorescence techniques to characterise the endolithic communities of phototrophic microorganisms in the skeleton of three
massive corals from a shallow reef flat. Microscopic observations and reflectance spectra showed the presence of up to four
distinct bands of photosynthetic microorganisms at different depths within the coral skeleton. Endolithic communities closer
to the coral surface exhibited higher photosynthetic electron transport rates and a green zone dominated by Ostreobium quekettii nearest the surface had the greatest chlorophyll pigment concentration. However, Ostreobium was also present and photosynthetically active in the colourless band between the coral tissue and the green band. The spectral
properties and pigment density of the endolithic bands were also found to closely correlate to photosynthetic rates as assessed
by fluorometry. All endolithic communities were extremely shade-adapted, and photosynthesis was saturated at irradiances <7 μmol
photons m−2s−1. |
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