title: IMAGING OF OXYGEN DYNAMICS WITHIN THE ENDOLITHIC ALGAL COMMUNITY OF THE MASSIVE CORAL PORITES LOBATA(1).
abstract: We used transparent planar oxygen optodes and a luminescence lifetime imaging system to map (at a pixel resolution of <200 μm) the two-dimensional distribution of O2 within the skeleton of a Porites lobata colony. The O2 distribution was closely correlated to the distribution of the predominant endolithic microalga, Ostreobium quekettii Bornet et Flahault that formed a distinct green band inside the skeleton. Oxygen production followed the outline of the Ostreobium band, and photosynthetic O2 production was detected at only 0.2 μmol photons m(-2)  · s(-1) , while saturation occurred at ∼37 μmol photons m(-2)  · s(-1) . Oxygen levels varied from ∼60% to 0% air saturation in the illuminated section of the coral skeleton in comparison to the darkened section. The O2 production within the Ostreobium band was lower in the region below the upward facing surface of the coral and elevated on the sides. Oxygen consumption in darkness was also greatest within the Ostreobium zone, as well as in the white skeleton zone immediately below the corallites. The rate of O2 depletion was not constant within zones and between zones, showing pronounced heterogeneity in endolithic respiration. When the coral was placed in darkness after a period of illumination, O2 levels declined by 50% within 20 min and approached steady-state after 40-50 min in darkness. Our study demonstrates the use of an important new tool in endolith photobiology and presents the first data of spatially resolved O2 concentration and its correlation to the physical structures and specific zones responsible for O2 production and consumption within the coral skeleton.
authors.affiliation: Marine Biological Laboratory, Department of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, DenmarkPCO AG, Research & Development, Donaupark 11, D-93309 Kelheim, GermanySchool of Biological Sciences, University of Sydney, Sydney, New South Wales, AustraliaInstitute for Water and Environmental Resource Management, University of Technology, Sydney, PO Box 123, Broadway 2007, New South Wales, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Kühl
authors.affiliation: Marine Biological Laboratory, Department of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, DenmarkPCO AG, Research & Development, Donaupark 11, D-93309 Kelheim, GermanySchool of Biological Sciences, University of Sydney, Sydney, New South Wales, AustraliaInstitute for Water and Environmental Resource Management, University of Technology, Sydney, PO Box 123, Broadway 2007, New South Wales, Australia.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Holst
authors.affiliation: Marine Biological Laboratory, Department of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, DenmarkPCO AG, Research & Development, Donaupark 11, D-93309 Kelheim, GermanySchool of Biological Sciences, University of Sydney, Sydney, New South Wales, AustraliaInstitute for Water and Environmental Resource Management, University of Technology, Sydney, PO Box 123, Broadway 2007, New South Wales, Australia.
authors.forename: Anthony W D
authors.initials: AW
authors.lastname: Larkum
authors.affiliation: Marine Biological Laboratory, Department of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, DenmarkPCO AG, Research & Development, Donaupark 11, D-93309 Kelheim, GermanySchool of Biological Sciences, University of Sydney, Sydney, New South Wales, AustraliaInstitute for Water and Environmental Resource Management, University of Technology, Sydney, PO Box 123, Broadway 2007, New South Wales, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Ralph
keywords: Ostreobium quekettii; endolithic; imaging; microenvironment; optode; oxygen