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Abstract

Microprofiles of oxygen and oxygenic photosynthesis were measured in a photosynthetically active sediment by an oxygen microelectrode. The di&.tsion coefficient of oxygen in the uppermost 1 mm of the sediment was determined in poisoned sediment by microelectrode measurement of changes in the oxygen profile during nonsteady state conditions. The experimentally obtained data were inserted into computer models to calculate the vertical profile of the oxygen consumption rate. The calculations showed that the rate of oxygen consumption was highest at the oxic-anoxic boundary where sulfide was oxidized and in the lowest part of the photic zone. Computer models were also used to obtain more accurate profiles of oxygen production. The oxygen profiles calculated by the computer were very close to those obtained experimentally both during the steady state developed under light and during the transient conditions developed at the onset of darkness.

Surfing in and on microbial mats: Oxygen-related behavior of a terminal Ediacaran bilaterian animal

“…Empirical measurements show that dissolved [O 2 ] in modern cyanobacterial mats can reach 4-8 PAL during the day, but it drops to essentially 0 PAL during the night, when a sulfidic environment develops (Canfield and des Marais, 1993;Wieland and Kühl, 2006;Gingras et al, 2011). These remarkable redox dynamics are also confirmed by the observation of [O 2 ] bubbles in cyanobacterial mats during the day (Bosak et al, 2010), which indicate [O 2 ] > 5 PAL, and by diffusion-reaction models parameterized with O 2 production and consumption rates as measured in modern microbial mats (Revsbech et al, 1986). Thus, although cyanobacterial mats can provide sufficient O 2 to support millimeter-sized mobile animals during the day, they are a challenging microenvironment for any animals that need even a moderate amount of O 2 throughout the light-dark cycle.…”

E-DATA: A Comprehensive Field Campaign to Investigate Evaporation Enhanced by Advection in the Hyper-Arid Altiplano

“…To study this link is motivated by the fact that the ecological description of these ecosystems indicates that the trophic chain is supported by benthic primary production (BPP) that occurs in the sediments of the saline lake [45][46][47]. BPP occurs in a thin active layer at the top of the sediments [25,48,49], and it is due to the photosynthesis of benthonic species such as benthic diatoms and cyanobacteria [6,50].…”

Monitoring microbial sulfate reduction in porous media using multipurpose electrodes

“…[36] Despite these limitations, the Ag/Ag 2 S electrode has for a long time offered the only reasonable solution to estimate sulfide at high spatial resolution at the aerobic and anaerobic interface in aquatic sediments and biofilms, where distinct gradients of chemical and physical parameters exist [Revsbech et al, 1986;Kühl and Jørgensen, 1992]. Electrode-based electrochemical determination of sulfide in aqueous system has a lower determination limit of a few ppb and an upper limit of hundreds of ppm, depending on the methods and electrodes [Lawrence et al, 2000].…”