MEPS 261:75-83 (2003)  -  doi:10.3354/meps261075

ABSTRACT: This paper presents a new non-invasive technique for measuring sediment O₂ uptake that, in its concept, differs fundamentally from other methods used to date. In almost all natural aquatic environments, the vertical transport of O₂ through the water column toward the sediment surface is facilitated by turbulent motion. The new technique relies on measuring 2 parameters simultaneously and at the same point in the water above the sediment: the fluctuating vertical velocity using an acoustic Doppler velocimeter and the fluctuating O₂ concentration using an O₂ microelectrode. From these 2 parameters, which typically are measured 10 to 50 cm above the sediment surface for a period of 10 to 20 min and at a frequency of 15 to 25 Hz, the vertical flux of O₂ toward the sediment surface is derived. Based on measurements performed under actual field conditions and comparisons with in situ flux-chamber measurements, we believe that this new technique is the optimal approach for determining O₂ uptake by sediments. The technique is superior to conventional methods as measurements are done under true in situ conditions, i.e. without any disturbance of the sediment and under the natural hydrodynamic conditions. Furthermore, this technique can be used for bio-irrigated or highly permeable sediments, such as sands, where traditional methods often fail. While this paper only focuses on O₂ uptake by sediments, the technique can also be applied to other solutes that can be measured at a sufficiently high temporal resolution.

KEY WORDS: Oxygen uptake · Sediment · Eddy-correlation measurements