Effect of elevated CO2 on the community metabolism of an experimental coral reef

The effect of elevated pCO2 on the metabolism of a coral reef community dominated by macroalgae has been investigated utilizing the large 2650 m3 coral reef mesocosm at the Biosphere‐2 facility near Tucson, Arizona. The carbonate chemistry of the water was manipulated to simulate present‐day and a doubled CO2 future condition. Each experiment consisted of a 1–2 month preconditioning period followed by a 7–9 day observational period. The pCO2 was 404 ± 63 μatm during the present‐day pCO2 experiment and 658 ± 59 μatm during the elevated pCO2 experiment. Nutrient levels were low and typical of natural reefs waters (NO3− 0.5–0.9 μM, NH4+ 0.4 μM, PO43− 0.07–0.09 μM). The temperature and salinity of the water were held constant at 26.5 ± 0.2°C and 34.4 ± 0.2 ppt. Photosynthetically available irradiance was 10 ± 2 during the present‐day experiment and 7.4 ± 0.5 mol photons m−2 d−1 during the elevated pCO2 experiment. The primary producer biomass in the mesocosm was dominated by four species of macroalgae; Haptilon cubense, Amphiroa fragillisima, Gelidiopsis intricata and Chondria dasyphylla. Algal biomass was 10.4 mol C m−2 during the present‐day and 8.7 mol C m−2 and during the elevated pCO2 experiments. As previously observed, the increase in pCO2 resulted in a decrease in calcification from 0.041 ± 0.007 to 0.006 ± 0.003 mol CaCO3 m−2 d−1. Net community production (NCP) and dark respiration did not change in response to elevated pCO2. Light respiration measured by a new radiocarbon isotope dilution method exceeded dark respiration by a factor of 1.2 ± 0.3 to 2.1 ± 0.4 on a daily basis and by 2.2 ± 0.6 to 3.9 ± 0.8 on an hourly basis. The 1.8‐fold increase with increasing pCO2 indicates that the enhanced respiration in the light was not due to photorespiration. Gross production (GPP) computed as the sum of NCP plus daily respiration (light + dark) increased significantly (0.24 ± 0.03 vs. 0.32 ± 0.04 mol C m−2 d−1). However, the conventional calculation of GPP based on the assumption that respiration in the light proceeds at the same rate as the dark underestimated the true rate of GPP by 41–100% and completely missed the increased rate of carbon cycling due to elevated pCO2. We conclude that under natural, undisturbed, nutrient‐limited conditions elevated CO2 depresses calcification, stimulates the rate of turnover of organic carbon, particularly in the light, but has no effect on net organic production. The hypothesis that an increase pCO2 would produce an increase in net production that would counterbalance the effect of decreasing saturation state on calcification is not supported by these data.

[1]  K. Asada,et al.  Influence of enhanced CO2 on growth and photosynthesis of the red algaeGracilaria sp. andG. chilensis , 1993, Journal of Applied Phycology.

[2]  A. Kaplan,et al.  Photosynthesis and the intracellular inorganic carbon pool in the bluegreen alga Anabaena variabilis: Response to external CO2 concentration , 1980, Planta.

[3]  R. Furbank,et al.  On the nature of the oxygen uptake in the light by Chondrus crispus. Effects of inhibitors, temperature and light intensity , 2004, Photosynthesis Research.

[4]  J. Raven,et al.  Exogenous inorganic carbon sources for photosynthesis in seawater by members of the Fucales and the Laminariales (Phaeophyta): ecological and taxonomic implications , 2004, Oecologia.

[5]  J. Jaubert,et al.  Primary production, respiration, and calcification of a coral reef mesocosm under increased CO2 partial pressure , 2002 .

[6]  C. Langdon,et al.  Production‐respiration relationships at different timescales within the Biosphere 2 coral reef biome , 2001 .

[7]  C. Langdon,et al.  Dependence of calcification on light and carbonate ion concentration for the hermatypic coral Porites compressa , 2001 .

[8]  C. Sweeney,et al.  Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef , 2000 .

[9]  J. Jaubert,et al.  CO2 partial pressure controls the calcification rate of a coral community , 2000 .

[10]  M. Bender,et al.  Net and gross production in the Ross Sea as determined by incubation experiments and dissolved O2 studies , 2000 .

[11]  E. Hochberg,et al.  The Biosphere 2 coral reef biome , 1999 .

[12]  Langdon,et al.  Geochemical consequences of increased atmospheric carbon dioxide on coral reefs , 1999, Science.

[13]  Denis Allemand,et al.  Photosynthesis and Calcification at Cellular, Organismal and Community Levels in Coral Reefs: A Review on Interactions and Control by Carbonate Chemistry , 1999 .

[14]  J. Gattuso,et al.  CARBON AND CARBONATE METABOLISM IN COASTAL AQUATIC ECOSYSTEMS , 1998 .

[15]  J. Gattuso,et al.  Contribution of soft-bottoms to the community metabolism (primary production and calcification) of a barrier reef flat (Moorea, French Polynesia) , 1998 .

[16]  Robert W. Buddemeier,et al.  Effect of calcium carbonate saturation of seawater on coral calcification , 1998 .

[17]  J. Gattuso,et al.  PRIMARY PRODUCTION, CALCIFICATION, AND AIR‐SEA CO2 FLUXES OF A MACROALGAL‐DOMINATED CORAL REEF COMMUNITY (MOOREA, FRENCH POLYNESIA) 1 , 1997 .

[18]  J. Houghton,et al.  Climate change 1995: the science of climate change. , 1996 .

[19]  Michael Kühl,et al.  Microenvironment and photosynthesis of zooxanthellae in scleractinian corals studied with microsensors for O2, pH and light , 1995 .

[20]  K. Asada,et al.  Calcification in the articulated coralline alga Corallina pilulifera, with special reference to the effect of elevated CO2 concentration , 1993 .

[21]  R. Wanninkhof.  Relationship between wind speed and gas exchange over the ocean , 1992 .

[22]  B. Osborne,et al.  Using Isotopes to Measure Gas Exchange , 1992 .

[23]  C. Osmond,et al.  INORGANIC CARBON LIMITATION OF PHOTOSYNTHESIS IN ULVA ROTUNDATA (CHLOROPHYTA) 1 , 1991 .

[24]  S. Maberly.  EXOGENOUS SOURCES OF INORGANIC CARBON FOR PHOTOSYNTHESIS BY MARINE MACROALGAE 1 , 1990 .

[25]  T. Kana.  Light-dependent oxygen cycling measured by an oxygen-18 isotope dilution technique , 1990 .

[26]  P. Falkowski,et al.  Respiratory losses in the light in a marine diatom: Measurements by short-term mass spectrometry. [Thalassiosira weisflogii] , 1989 .

[27]  C. Langdon,et al.  Rates of respiration in the light measured in marine phytoplankton using an 18O isotope-labelling technique , 1989 .

[28]  D. Turpin,et al.  Mitochondrial Respiration Can Support NO(3) and NO(2) Reduction during Photosynthesis : Interactions between Photosynthesis, Respiration, and N Assimilation in the N-Limited Green Alga Selenastrum minutum. , 1989, Plant physiology.

[29]  D. Turpin,et al.  Ammonium Assimilation Requires Mitochondrial Respiration in the Light : A Study with the Green Alga Selenastrum minutum. , 1988, Plant physiology.

[30]  K. Johnson,et al.  A comparison of four methods for determining planktonic community production1 , 1987 .

[31]  M. Bender,et al.  Production, respiration and the isotope geochemistry of O2 in the upper water column , 1987 .

[32]  B. Jähne,et al.  On the parameters influencing air‐water gas exchange , 1987 .

[33]  H. Fock,et al.  Effect of Photon Fluence Rate on Oxygen Evolution and Uptake by Chlamydomonas reinhardtii Suspensions Grown in Ambient and CO(2)-Enriched Air. , 1986, Plant physiology.

[34]  P. Buat-Ménard.  The role of air-sea exchange in geochemical cycling , 1986 .

[35]  L. Merlivat,et al.  Air-Sea Gas Exchange Rates: Introduction and Synthesis , 1986 .

[36]  R. Carpenter,et al.  Relationships between primary production and ii radiance in coral reef algal communities1 , 1985 .

[37]  D. Kinsey.  Metabolism, calcification and carbon production. I. System level studies , 1985 .

[38]  Bruce B. Benson,et al.  The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere1 , 1984 .

[39]  J. R. Coleman,et al.  Measurement of photorespiration in algae. , 1982, Plant physiology.

[40]  S. V. Smith.  The Houtman Abrolhos Islands: Carbon metabolism of coral reefs at high latitude1 , 1981 .

[41]  M. Borowitzka.  Photosynthesis and calcification in the articulated coralline red algae Amphiroa anceps and A. foliacea , 1981 .

[42]  A. Kaplan,et al.  Internal Inorganic Carbon Pool of Chlamydomonas reinhardtii: EVIDENCE FOR A CARBON DIOXIDE-CONCENTRATING MECHANISM. , 1980, Plant physiology.

[43]  M. Borowitzka,et al.  Calcification in the Green Alga Halimeda III. THE SOURCES OF INORGANIC CARBON FOR PHOTOSYNTHESIS AND CALCIFICATION AND A MODEL OF THE MECHANISM OF CALCIFICATION , 1976 .

[44]  A. Larkum,et al.  Calcification in the Green Alga Halimeda , 1976 .

[45]  D. Graham,et al.  The Effect of Light on the Tricarboxylic Acid Cycle in Green Leaves: II. Intermediary Metabolism and the Location of Control Points. , 1974, Plant physiology.

[46]  C. Osmond,et al.  The Effect of Light on the Tricarboxylic Acid Cycle in Green Leaves: III. A Comparison between Some C(3) and C(4) Plants. , 1974, Plant physiology.

[47]  Stephen V. Smith,et al.  ORGANIC CARBON PRODUCTION ON THE WINDWARD REEF FLAT OF ENIWETOK ATOLL1 , 1973 .

[48]  M. Gibbs,et al.  Effect of Light on the Tricarboxylic Acid Cycle in Scenedesmus. , 1965, Plant physiology.

[49]  B. Copeland,et al.  USE OF A CLEAR PLASTIC DOME TO MEASURE GASEOUS DIFFUSION RATES IN NATURAL WATERS , 1964 .

[50]  H. Odum,et al.  Trophic Structure and Productivity of a Windward Coral Reef Community on Eniwetok Atoll , 1955 .