Eddy covariance


Roughly a third of the global carbon mineralization and nutrient cycling in the ocean occurs on the continental margins, but available in-situ measurements of these processes are remarkably few, leaving their dynamics and controls are not well understood. This deficiency reduces the accuracy of local and global carbon budgets. We develop, test and deploy Eddy Covariance instruments, a technique that permits non-invasive oxygen flux measurements at the seafloor. Oxygen fluxes measured across the sediment-water interface are the main proxy for assessing carbon cycling rates in sediments and are used widely in carbon budget estimates. Eddy Covariance measurements do not interfere with the flow and light regime at the site for which the flux is determined, allowing more reliable flux measurements in shallow, energetic coastal environments. Further goals are to enhance the accessibility of the Eddy Covariance Instrument to users, and to further develop this technique to allow long-term deployments in monitoring programs.

There are several reasons why the benthic oxygen flux is a good measure for assessing carbon cycling rates in sediments: Oxygen is thermodynamically the most favorable electron acceptor in reactions consuming organic matter, and its consumption thus reflects the mineralization of organic carbon where anaerobic mineralization products are fully oxidized within the seabed. Oxygen also is presently the only electron acceptor that can be measured at the high temporal and spatial resolutions necessary to follow all rapid changes in sediment-water fluxes. Because changes in benthic oxygen fluxes occur on temporal and spatial scales covering several orders of magnitude, determination of representative oxygen fluxes is a challenging task with invasive techniques.