title: Photosynthetic response to globally increasing CO2 of co-occurring temperate seagrass species.
abstract: Photosynthesis of most seagrass species seems to be limited by present concentrations of dissolved inorganic carbon (DIC). Therefore, the ongoing increase in atmospheric CO2 could enhance seagrass photosynthesis and internal O2 supply, and potentially change species competition through differential responses to increasing CO2 availability among species. We used short-term photosynthetic responses of nine seagrass species from the south-west of Australia to test species-specific responses to enhanced CO2 and changes in HCO3 (-) . Net photosynthesis of all species except Zostera polychlamys were limited at pre-industrial compared to saturating CO2 levels at light saturation, suggesting that enhanced CO2 availability will enhance seagrass performance. Seven out of the nine species were efficient HCO3 (-) users through acidification of diffusive boundary layers, production of extracellular carbonic anhydrase, or uptake and internal conversion of HCO3 (-) . Species responded differently to near saturating CO2 implying that increasing atmospheric CO2 may change competition among seagrass species if co-occurring in mixed beds. Increasing CO2 availability also enhanced internal aeration in the one species assessed. We expect that future increases in atmospheric CO2 will have the strongest impact on seagrass recruits and sparsely vegetated beds, because densely vegetated seagrass beds are most often limited by light and not by inorganic carbon.
authors.affiliation: Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd floor, 2100, Copenhagen, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Borum
authors.affiliation: Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd floor, 2100, Copenhagen, Denmark.|Institute of Advanced Studies, The University of Western Australia, Crawley, 6009, WA, Australia.|School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia.
authors.forename: Ole
authors.initials: O
authors.lastname: Pedersen
authors.affiliation: School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Kotula
authors.affiliation: School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia.|Oceans Institute, The University of Western Australia, Crawley, 6009, WA, Australia.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Fraser
authors.affiliation: School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia.|Oceans Institute, The University of Western Australia, Crawley, 6009, WA, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Statton
authors.affiliation: School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Colmer
authors.affiliation: School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia.|Oceans Institute, The University of Western Australia, Crawley, 6009, WA, Australia.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Kendrick
mesh_terms: D035961:Alismatales / Q000378:metabolism* / Q000502:physiology; D059001:Aquatic Organisms / Q000378:metabolism / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D057231:Climate Change; D031321:Hydrocharitaceae / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D019684:Magnoliopsida / Q000378:metabolism* / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D014904:Western Australia; D035962:Zosteraceae / Q000378:metabolism* / Q000502:physiology
chemical_list: D002734:Chlorophyll; D002245:Carbon Dioxide; D010100:Oxygen
keywords: bicarbonate utilization; increasing atmospheric CO2; internal aeration; net photosynthesis