PDFFirst Paragraph
The eddy correlation technique has been used for 60 years in atmospheric boundary layer research to measure land-air exchanges of different constituents (e.g., Swinbank, 1951). Only recently, the technique has also been applied to the benthic boundary layer by Berg et al. (2003), who determined sediment-water fluxes of dissolved O2 and validated their findings against in situ chamber measurements. It is technically challenging to measure the key eddy correlation variables at a point near the sediment-water interface and at the high frequency required to fully resolve turbulent eddies. However, if feasible, the reward is high in that major limitations inherently linked to other flux methods, such as lab measurements in sediment cores and deployments of in situ chambers, can be bypassed. Specifically, eddy correlation measurements integrate over a larger area (Berg et al., 2007) and are done under true in situ conditions with no disturbances of sediment, light, and bottom boundary layer flow. The latter is particularly important for permeable sediments, where current and wave-driven porewater flushing can significantly alter biogeochemical cycling (Huettel et al., 1998; Jahnke et al., 2000; Reimers et al., 2004). As methodological bias is minimized, this technique can significantly improve monitoring at the seafloor.