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The effect of sediment-dwelling macrofauna on nitrifying bacteria was investigated by direct probing in their overlapping habitat, i.e., the upper few millimeters of freshwater sediments. Microsensors (O 2 , NH þ 4 , NO 2 3 , and diffusivity) were used at the sediment surface and inside animal burrows to record steady-state and dynamic distributions of(More)
Oxygen distribution and benthic mineralization rates were investigated in a permeable intertidal sand flat (permeability: 3.9 3 10 211 m 2) in a transect from the low toward the high waterline. At all stations, oxygen penetrated several millimeters to centimeters into the sediments during inundation because of pore-water advection. The wave-and(More)
From the Hå kon Mosby Mud Volcano (HMMV) on the southwest Barents Sea shelf, gas and fluids are expelled by active mud volcanism. We studied the mass transfer phenomena and microbial conversions in the surface layers using in situ microsensor measurements and on retrieved cores. The HMMV consists of three concentric habitats: a central area with gray mud, a(More)
Aerobic respiration plays an important role in the degradation of carbon and is typically estimated to account for 25% to 50% of carbon mineralization in coastal sediments. Two established methods have been used for the determination of areal oxygen consumption rates (OCR) in sediments, namely the dif-fusive oxygen uptake and the benthic-chamber total(More)
A new CO, microelectrode with a tip diameter of 10 pm and a response time (t,,) of-10 s is presented. The sensor allows CO, measurements with a detection limit of <3 PM. The microsensor was tested in experimental systems of increasing complexity. A diffusion-reaction simulation model was used to calculate CO, profiles in order to check the reliability of(More)
Sulfidic seeps with methane ebullition were observed at the low-water line of intertidal sand flats at a number of locations in the Wadden Sea. Bioturbating fauna was absent in the seep areas but abundant in the more central areas of the tidal flat. At one site, the vertical methane and sulfate distribution in pore water was determined along transects from(More)
Epilithic and endolithic biofilms were found to control the formation of stromatolites in karst-water creeks. We used microsensors to determine the influence of biological processes on chemical conditions within the microenvironment of crystal nucleation sites: the stromatolite surface. Phototrophic members of the biofilms consisted of mainly cyanobacteria(More)
Cyanobacteria and diatom mats are ubiquitous in hypersaline environments but have never been observed in the Dead Sea, one of the most hypersaline lakes on Earth. Here we report the discovery of phototrophic microbial mats at underwater freshwater seeps in the Dead Sea. These mats are either dominated by diatoms or unicellular cyanobacteria and are(More)
Microbial iron oxyhydroxides are common deposits in natural waters, recent sediments, and mine drainage systems. Along with these minerals, trace and rare earth elements (TREE) are being accumulated within the mineralizing microbial mats. TREE patterns are widely used to characterize minerals and rocks, and to elucidate their evolution and origin. However,(More)