Sediment-water exchange of O2 is a key parameter in biogeochemical studies of marine systems. The first phase of this project will improve the ability to measure O2 through further development of the eddy correlation technique. This development will enhance both the accessibility of the technique to users in general and the potential for long-term deployment of the eddy correlation technique in observatory systems like ORION and NEON. In the second phase, the technique will be used to study the complex dynamic nature of transport, consumption, and production of O2 at the sediment-water interface. This technique is superior to traditional methods for many applications in marine systems as there is no disturbance of the sediment, it is conducted under natural hydrodynamic and light conditions, and it can be used specifically for highly permeable or vegetated sediments where traditional methods fail. The strong interest in this technique is currently hindered as the technique demands custom-made components and specialized programming of both sampling scheme and flux extraction algorithms. This project will develop the eddy correlation technology to a stage where the instrument can be built with off-the-shelf components. Furthermore, it includes production of user-friendly software for extracting fluxes from measured data and estimation of other key parameters such as the size of the sediment surface area that contributes to the O2 flux and turbulent properties related to the O2 transport in the benthic boundary layer. The Clark-type O2 sensor used in eddy correlation measurements today is inherently fragile and prohibits the use of the technique in observatory systems such as ORION and NEON. For that reason, a more robust optical O2 sensor will be tested. Study sites will include fine-grained cohesive and sandy permeable sediments
