Aquatic Eddy covariance system for ecological and environmental research

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Water flow delivers dissolved gases such as oxygen, nutrients, and chemical signals to and from aquatic organisms and bottom sediments, as well as imparting forces on them.  An understanding of how oxygen is produced by aquatic plants, consumed in sediments by biogeochemical processes, or delivered from surface waters are vital and essential questions to ask about aquatic ecosystems. Moreover, such understanding can provide an indication of the health of aquatic environments and help to evaluate the effectiveness of control strategies.  Funds are requested for the purchases of an Eddy Covariance System to measure the oxygen flux in underwater habitats in lakes, rivers, and oceans.  The ability to measure the flux of oxygen under turbulent conditions in the field represents a significant improvement over traditional techniques involving laboratory incubations or field chambers, which are invasive and cannot be applied at large spatial scales or to complex shapes.  The eddy covariance system combines a specially designed 25 ?m diameter oxygen sensor and fast-response amplifier with a fast-response acoustic Doppler velocimeter.  The system works by making rapid (e.g., 64 Hz) and simultaneous measurements of water velocity (in three dimensions) and dissolved oxygen concentration in the same sampling volume.  These measurements can be decomposed into average and fluctuating components and the average of the product of the fluctuation components (u'c') provides the net turbulent flux.  The ability to measure oxygen flux in situ will represents a significant advance in our ability to determine the causes of low oxygen levels in lakes, the health of endangered freshwater mussel species, as well as the productivity of aquatic vegetation. This information will also lead to advances in the development of bio-physical and mathematical models of aquatic environments.