Oxygen evolution in a hypersaline crust:in situ photosynthesis quantification by microelectrode profiling and use of planar optode spots in incubation chambers

Abstract

Net primary production and respiration were estimated in a hypersaline cyanobacterial mat colonizing a gypsum crust in the Eilat salterns, Israel. Two different approaches were used: in situ microprofiling with Clark-type O 2 sensors and application of optode sensor spots in incubation chambers. The net O2 release rates of the mat phototrophs was high, with a maximum of 3.4 nmol O2 cm-2min-1measured by microprofiling and 4.4 nmol O2 cm-2min -1determined in the incubation chambers. The upper 2 layers of the mat as well as the overlying water quickly became O2 saturated during the day. The respiration of the whole gypsum crust was also very intensive and corresponded to the O2 produced by photosynthesis on a diurnal basis, which prevented most of the evolved O2 from reaching the water. The results presented show that optode sensor spots are useful tools providing additional information about export and photosynthetic production rates of O2 in hypersaline microbial mats. © Inter-Research 2009.