title: Enhanced photoprotection pathways in symbiotic dinoflagellates of shallow-water corals and other cnidarians.
abstract: Photoinhibition, exacerbated by elevated temperatures, underlies coral bleaching, but sensitivity to photosynthetic loss differs among various phylotypes of Symbiodinium, their dinoflagellate symbionts. Symbiodinium is a common symbiont in many cnidarian species including corals, jellyfish, anemones, and giant clams. Here, we provide evidence that most members of clade A Symbiodinium, but not clades B-D or F, exhibit enhanced capabilities for alternative photosynthetic electron-transport pathways including cyclic electron transport (CET). Unlike other clades, clade A Symbiodinium also undergo pronounced light-induced dissociation of antenna complexes from photosystem II (PSII) reaction centers. We propose these attributes promote survival of most cnidarians with clade A symbionts at high light intensities and confer resistance to bleaching conditions that conspicuously impact deeper dwelling corals that harbor non-clade A Symbiodinium.
authors.affiliation: Odum School of Ecology and Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: Jennifer McCabe
authors.initials: JM
authors.lastname: Reynolds
authors.forename: Brigitte U
authors.initials: BU
authors.lastname: Bruns
authors.forename: William K
authors.initials: WK
authors.lastname: Fitt
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Schmidt