Coral Reef Primary Production and Calcification: Quantitative Analysis of Sensitivity to Environmental Forcing using a Control Volume Approach

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The oceans are currently experiencing both warming and acidification due to the effects of increasing atmospheric CO2 levels, with surface ocean pH expected to drop by at least 0.3 pH units by the year 2100. Coral reefs are especially vulnerable to both factors. In this research, scientists from Stanford University will focus on the effects of acidification, combining novel methods and approaches from the fields of engineering, physical oceanography, and marine biogeochemistry to develop a quantitative understanding of the flow of carbon throughout the physical environment and varied communities of a healthy coral reef. During four field seasons at Heron Island Marine Station, located on the Great Barrier Reef, they will make the first simultaneous and in situ measurements of Net Community Production/Respiration and Net Community Calcification/Dissolution on a large intact coral reef tract by determining water column inorganic carbon system properties along the boundaries of a 3-dimensional control volume (CV). The overall goals of the proposed research are to: 1) Quantify how energy flows between a coral reef and the open ocean, and within different reef environments, by direct, in situ measurements of carbon system fluxes; 2) Describe diurnal, seasonal, and interannual variability in primary production and calcification and their dependency on flow regime and carbonate saturation state; and 3) Develop predictive assessments regarding the interactive response of coral reef systems to ongoing perturbations of global climate and the carbon cycle. To achieve these goals, the PIs will install an array of current meters, wave gauges, and thermistors to determine the hydrodynamic regime within the control volume at a spatial scale of 10 cm and time scale of seconds. Then, using the Reynolds Transport Theorem and water column carbon chemistry data, they will calculate net fluxes through each of the four CV faces and the surface boundary, and thereby determine net carbon fluxes between the benthic community and the overlying water.Broader impacts includes student mentoring, international collaboration, and outreach efforts. Stanford University conducts an overseas study program in Australia that will permit 3 to 5 undergraduate students to participate in this project for their honors thesis. Scientists from developing nations, such as Indonesia, Papua New Guinea, or other western Pacific nations, will also gain experience in geochemical monitoring of the coastal ocean. The PIs will also work with museum experts to develop a museum exhibit on ocean acidification and coral reefs.