1.2
Eddy Covariance measurements of CO2 exchange during monsoon and winter conditions over Heron Reef, southern Great Barrier Reef, Australia
Hamish A. McGowan, The University of Queensland, Brisbane, Queensland, Australia; and M. C. MacKellar
Coral reefs cover approximately 2.8 to 6.0 x 105 km2 of the Earth's tropical and subtropical oceans and are among the most biologically diverse and economically important ecosystems on the planet. However relatively little information exists on the role of coral reefs in air-sea CO2 exchange. It was thought that coral reefs were sinks of CO2 because precipitation of CaCO3 results in sequestering of carbon. However, the associated change in pH results in a release of CO2 which has been estimated to be equal to 0.4 to 1.4% of anthropogenic CO2 emissions. While these values are not great they need to be confirmed through direct measurement so that the role of coral reefs in carbon budgets can be accurately quantified.
In this paper we present results from the first in-situ Eddy Covariance measurements of air-sea CO2 exchange conducted over the 344,400 km2 Great Barrier Reef, Australia. Measurements were made in June 2009 (austral winter) and February 2010 (austral summer) using pontoon mounted eddy covariance systems at Heron Reef (23°26.577S, 151°26.577E) in the Capricorn Bunker Group of the southern Great Barrier Reef. Results show that during summer under monsoonal conditions the shallow reef flat was found to be a net source of CO2, particularly at night while the shallow and deep lagoons of Heron Reef were net sinks. Concurrent measurements of CO2 exchange over the shallow reef flat and ocean adjacent to Heron Reef found the ocean to be a CO2 sink. During winter net CO2 sequestration was found to be significantly greater than in summer. A simple CO2 budget based on these results is presented indicating that reefs such as Heron Reef in the southern Great Barrier Reef act as CO2 sinks.
Session 1, Air-Sea Flux Estimation and Parameterization: 1. Observations
Monday, 27 September 2010, 10:30 AM-12:00 PM, Capitol AB
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