Starting in autumn 2015, our research group investigates oxygen and pH profiles in the sea surface microlayer at the interface between the atmosphere and seawater. For this purpose, an aquarium tank has been filled with 800L of seawater at the Terramare in Wilhelmshaven. For profiling, we use microsensors developed by Unisense. Profile measurement of the water column are performed in 50µm steps by using a computer-operated motor unit, i.e. the microsensors enable profiling of the surface microlayer in very high resolution. The aquarium has been additionally equipped with white light lamps and UV light as well as a wave generator to allow simulation of naturally-occurring abiotic factors and to study their impact on the biology of the surface layer.
In a first approach in November, Christian and Janina tested for the sensitivity and precision of the microsensors to establish a general protocol for the calibration and measurement procedure. First measurements between seawater (including organisms) and sterile-filtered seawater (without organisms) revealed differences in oxygen profiles for the upper few centimeters of the water column. Furthermore, the microsensors were used in a first incubation set-up, comparing oxygen consumption and production in the surface layer and subsurface water. During this experiment, samples were taken to determine cell numbers and diversity of the microbial community of the surface layer.