title: EFFECTS OF MODERATE HEAT STRESS AND DISSOLVED INORGANIC CARBON CONCENTRATION ON PHOTOSYNTHESIS AND RESPIRATION OF SYMBIODINIUM SP. (DINOPHYCEAE) IN CULTURE AND IN SYMBIOSIS(1).
abstract: The influence of temperature and inorganic carbon (Ci ) concentration on photosynthesis was examined in whole corals and samples of cultured symbiotic dinoflagellates (Symbiodinium sp.) using combined measurements from a membrane inlet mass spectrometer and chl a fluorometer. In whole corals, O2 production at 26°C was significantly limited at Ci concentrations below ambient seawater (∼2.2 mM). Further additions of Ci up to ∼10 mM caused no further stimulation of oxygenic photosynthesis. Following exposure to 30°C (2 d), net oxygen production decreased significantly in whole corals, as a result of reduced production of photosynthetically derived oxygen rather than increased host consumption. Whole corals maintained a rate of oxygen evolution around eight times lower than cultured Symbiodinium sp. at inorganic carbon concentrations <2 mM, but cultures displayed greater levels of photoinhibition following heat treatment (30°C, 2 d). Whole corals and cultured zooxanthellae differed considerably in their responses to Ci concentration and moderate heat stress, demonstrating that cultured Symbiodinium make an incongruous model for those in hospite. Reduced net oxygen evolution, in whole corals, under conditions of low Ci (<2 mM) has been interpreted in terms of possible sink limitation leading to increased nonphotochemical energy dissipation. The advantages of combined measurement of net gas exchange and fluorometry offered by this method are discussed.
authors.affiliation: Department of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, AustraliaARC Centre of Excellence in Plant Energy Biology, Molecular Plant Physiology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, AustraliaDepartment of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, Australia.
authors.forename: Lucy
authors.initials: L
authors.lastname: Buxton
authors.affiliation: Department of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, AustraliaARC Centre of Excellence in Plant Energy Biology, Molecular Plant Physiology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, AustraliaDepartment of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, Australia.
authors.forename: Murray
authors.initials: M
authors.lastname: Badger
authors.affiliation: Department of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, AustraliaARC Centre of Excellence in Plant Energy Biology, Molecular Plant Physiology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, AustraliaDepartment of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Ralph
keywords: Symbiodinium; carbon dioxide; coral; inorganic carbon; membrane inlet mass spectrometer; photosynthesis; temperature; zooxanthellae