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Marine Ecology Progress Series

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MEPS 361:139-150 (2008)  -  DOI:

Seasonal variation in the photo-physiology of homogeneous and heterogeneous Symbiodinium consortia in two scleractinian corals

K. E. Ulstrup1,2,4,*, R. Hill1, M. J. H. van Oppen2, A. W. D. Larkum3, P. J. Ralph1

1Institute for Water & Environmental Resource Management, Department of Environmental Science, University of Technology, Sydney, PO Box 123, Broadway, New South Wales 2007, Australia
2Australian Institute of Marine Science, PMB No. 3, Townsville MC, Queensland 4810, Australia
3School of Biological Sciences (A08), University of Sydney, New South Wales 2006, Australia
4Present address: Marine Biological Laboratory, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark

ABSTRACT: Seasonal variation in the composition of the algal endosymbiont community and photo-physiology was determined in the corals Pocillopora damicornis, which show high local fidelity to one symbiont type (Symbiodinium C1), and Acropora valida, with a mixed Symbiodinium symbiont community, comprising members of both clades A and C. The relative abundances of Symbiodinium types varied over time. A significant decline in symbiont densities in both coral species during the summer of 2005 coincided with a NOAA ‘hotspot’ warning for Heron Island. This also coincided with a relative increase in the presence and dominance of clade A in A. valida, particularly in sun-adapted surfaces. The effective quantum yield of Photosystem II (ΦPSII) suggested that sun-adapted surfaces of P. damicornis are more sensitive than shade-adapted surfaces to combined effects of higher temperature and irradiance in summer. Xanthophyll cycling was greater in P. damicornis than A. valida, irrespective of branch position and sampling time; this may be a mechanism by which P. damicornis compensates for its fidelity to Symbiodinium C1. Furthermore, xanthophyll de-epoxidation in P. damicornis symbionts was greater in sun-adapted than shade-adapted surfaces, correlating with non-photochemical quenching (NPQRLC). No variation was found in A. valida, indicating that resident symbiont communities may not have been physiologically compromised, perhaps as a result of changes in the composition of the Symbiodinium community consortia.

KEY WORDS: Fast fluorescence kinetics · ITS1 rDNA · LSU rDNA · Symbiodinium · Symbiont density

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Cite this article as: Ulstrup KE, Hill R, van Oppen MJH, Larkum AWD, Ralph PJ (2008) Seasonal variation in the photo-physiology of homogeneous and heterogeneous Symbiodinium consortia in two scleractinian corals. Mar Ecol Prog Ser 361:139-150.

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