MEPS 136:277-287 (1996)  -  doi:10.3354/meps136277

Respiration, the biochemical transfer of electrons along respiratory chains, provides energy for maintenance and growth. Measurements of the activity of the respiratory electron transport system (ETS) have been adapted for marine studies since the 1970s. In this paper, the application of ETS activity measurements to marine sediment samples is discussed and a review of literature data is presented. From a technical point of view, extraction efficiency of the respiratory units during homogenization is the main difficulty in applying the method to sediment. It has been recognized that time- and temperature-controlled ultrasonic disruption is the most efficient extractionmethod. The dilution of the homogenate is also of critical importance for efficient recovery of ETS activity. A new, accurate method using microtitration techniques is given for laboratory and shipboard applications. Published data show that ETS activity in marine surface sediments, expressed at 20*C, decreases strongly from coastal zones (mean: 186 ul O₂ h^-1 g^-1) to the shelf (38 ul O₂ h^-1 g^-1) and to deep sea areas (less than 5 ul O₂ h^-1 g^-1), with an inflexion in the gradient at the upper continental slope. However, at least in some cases, a slight increase can be noted down the slope, where continental margins are thought to receive important carbon fluxes. Within sediment, ETS decreases generally from the surface to deeper layers. For sediments from oligotrophic areas, the gradient is regular and ETS becomes undetectable deeper than 10 to 15 cm. However, in coastal zones, high subsurface activity levels are often found just below the oxic zone, and ETS activity is still present in deep (more than 30 cm), anoxic layers.

ETS activity in sediments