University of Koblenz-Landau (Germany), Institute for Environmental Sciences

Optical oxygen microsensors OXR50 from PyroScience were used to investigate potential horizontal variations in the oxygen gradient over the redoxcline of a small meromictic lake.

8 needle-type oxygen microsensors (OXR50) were attached to a rod with a distance of 10 cm between the sensors. A thermistor logger was applied right next to each of the FireSting oxygen sensors to compensate the measured oxygen values for temperature effects later on. The rod with the sensors was mounted on the stern of a boat, submersed vertically into the water. The oxygen sensors were connected via 2 FireSting oxygen meters (4-channel versions, FSO2-4) with a laptop. The laptop provided power supply and data acquistion for the FireSting oxygen meters, enabling on board inspection and data logging of the measured oxygen data. Figure 1 shows the oxygen sensors and thermistor loggers attached to the rod and connected via the 2 FireSting to a laptop. This setup enabled us to measure continuous depth profiles of dissolved oxygen, while we drove with constant speed along transects across the lake. The oxygen saturation measured on 29th of September 2011 for a depth range of 0.7 - 1.3 m along the East-West axis of the lake Waldsee (Germany) is shown in Figure 2.

These measurements were conducted as a part of the project entitled “RedoxFlux” at the University of Koblenz-Landau (Germany), which dealt with biogeochemical fluxes and transformations at pelagic redoxclines in lakes.

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