PRIMARY PRODUCTION, CALCIFICATION, AND AIR‐SEA CO₂ FLUXES OF A MACROALGAL‐DOMINATED CORAL REEF COMMUNITY (MOOREA, FRENCH POLYNESIA)¹

Abstract

Community metabolism and air-sea carbon dioxide (COJ jluxes were investigated in July 1992 on a finging reef at Momea (Frach Polynesia). The benthic community was dominated by macroalgae (85 % substratum cover) and comprised of Phaeophyceae Padina tenuis (Bmy), Turbinaria ornata (Turner) J. Agardh, and Hydroclathrus clathratus Bmy (Howe); Chlorophyta Halimeda incrassata $ ovata J. Agardh (Howe); and Ventricaria ventricosa J. Agardh (Olsen et West), as well as several Rhodophyta (Actinotrichia fragilis Forskal (Bargesen) and several species of encrusting coralline algae). Algal biomass was 171 g dry weight-m-,. Community gross production pK), respiration (R), and net calcijication (G) were measured in an opentop enclosure. P and R were respectively 248 and 240 mmol (20,-m-,. &I, and there was a slight net dissolution of CaCO, (0.8 mmoEm-2.d-1). This site was a sink for atmospheric CO, (10 ? 4 mmol CO,.m-z*d-l), and the analysis of data j o m the literature suggests that this is a general feature of algaldominated reefs. Measurement of air-sea CO, Juxes in open water close to the enclosure demonstrated that changes in small-scale hydrodynamics can lead to misleading conclusions. Net CO, evasion to the atmosphere was measured on the fingzng reef due to changes I in the cuwent pattern that drove waterjom the barrier reef (a CO, source) to the study site. IGJ index words: cmal re& algal-dominated; calcijication; community metabolism; air-sea CO, jlux; pn'mary productionCoral reef ecosystems are dominated by photosynthetic and calcifylng organisms such as scleractinian corals and macroalgae. They are therefore well suited to investigating the effect of the metabolism of organic (photosynthesis and respiration) and inorganic (precipitation and dissolution of CaCO,) carbon of benthic communities on the seawater inorganic carbon system. These biological processes can induce large changes in the partial pressure of carbon dioxide (pCO,), which controls air-sea CO, fluxes.The chemistry of carbon dioxide (CO,) in natural water is quite complex because dissolved C 0 2 combines with water to generate bicarbonate (HCO,) and carbonate (COi-) ions. The concentrations of those three species of inorganic carbon are controlled by equilibrium constants that depend on temperature, salinity, and pressure. Production and degradation of 1 mole of organic matter by photosynthesis and respiration respectively decreases and increases dissolved inorganic carbon (DIC) (DIC = [CO,] + [HCO;] + [COq-1) by approximately 1 mole: 729

High‐resolution carbon budgets on a Palau back‐reef modulated by interactions between hydrodynamics and reef metabolism

“…Coral reef metabolism-Canonically, coral reef metabolism refers to the balance between inorganic and organic carbon cycling processes on reefs, a concept that incorporates both calcification and dissolution by skeleton-building organisms, as well as photosynthesis by local primary producers and respiration by all reef dwellers (Gattuso 1999). NEC rates were determined in this study based on the alkalinity anomaly technique, developed and validated by Smith and Key (1975), Gattuso et al (1999), Yates and Halley (2006), Silverman et al (2007Silverman et al ( , 2012, Shamberger et al (2011), andShaw et al (2012).…”

“…NEC rates were determined in this study based on the alkalinity anomaly technique, developed and validated by Smith and Key (1975), Gattuso et al (1999), Yates and Halley (2006), Silverman et al (2007Silverman et al ( , 2012, Shamberger et al (2011), andShaw et al (2012). For every mole of CaCO 3 precipitated, TA decreases by 2 moles and DIC is reduced by 1 mole (Gattuso et al 1999). We calculate NCC (mmol m 22 h 21 ), air-sea CO 2 flux (F CO 2 ; mmol m 22 h 21 ) and NCP (mmol m 22 h 21 ) via the following equations:…”

“…Laboratory studies provide valuable species-specific information, but can potentially miss synergistic abiotic forcings and ecological factors. Shore-based mesocosms (Jokiel et al 2008;Andersson et al 2009) and ''chamber''-type in situ mesocosms on reefs and benthic enclosures (e.g., the Submersible Habitat for Analyzing Reef Quality) using pumps to simulate water flow (Gattuso et al 1997;Yates and Halley 2006) provide quantitative estimates for reef metabolism on the time scale of hours, yet lack natural water circulation and movement of nutrients, carbon, and organisms.…”

“…However, both Eulerian (Atkinson and Bilger 1992; Gattuso et al 1993Gattuso et al , 1996 and Lagrangian (Barnes and Lazar 1993;Frankignoulle et al 1996) studies rely heavily on the assumption that the water column above the benthic community is fully mixed. Often in waters deeper than 3 m, the water column is sheared, so fluxes estimated from gradual changes in concentration using integration over the full depth of the environment can be erroneous.…”

Morphological characterisation of reef types in Torres Strait and an assessment of their carbonate production

“…Brock et al, 2006;Gattuso et al, 1997;Yates and Halley, 2003), although empirical studies suggest calcification is reducing as a result of increase in sea surface temperature and partial pressure of CO 2 (Silverman et al, 2009). Kinsey and Hopley (1991) derived generalized gross production rates (G values) for intra-reef geomorphic zones in the GBR based on a combination of 3 absolute modes defined by Kinsey (1979).…”