Working Area was the central Baltic Sea from Farö Deep to the Southern Gotland Basin encirceled by the south bound latitude 54.188, west bound longitude of 12.081, north bound latitude of 58.001 and in the east bound by longitude 20.652.
The distribution and cycling of manganese (Mn) species across the redox boundary in the central Baltic Sea was studied by a team of researchers from the IOW and WHOI with the aim to interrogate possible links between Mn and the nitrogen (N), oxygen (O), and iodine (I) cycles, taking into account the role of Mn(III)-ligand complexes and reactive Mn oxide particles. The role of reactive Mn species in controlling the redox state of stratified waters, using novel in situ instrumentation, high resolution water sampling, and targeted solid-phase characterization was done by normal CTD and pump CTD casts. Profiles of reactive oxygen species (ROS), showed slight variation throughout the day tentatively suggesting other sources than light as a reason. Seven pump CTD casts (EMB_2 to EMB_8) were the first measured in the Baltic Sea.
About the Data:
The upper pycnocline coincided with a temperature drop of approx. 10 °C from near 15 °C to around 5 °C. The temperature was stable until the second pycnocline from where it rose to approx. 7 °C and stayed stable to close to the seafloor
Oxygen profiles resemble each other even though the concentrations are different
below the first pycnocline.
At stations go27, TF271, go23 and TF260 the concentration decreased to either the detection limit (stations TF271 and go23) or around 20 μmol L- 1 (stations go and TF260). Below the pycnocline several oxygen peaks occurred with concentrations up to 40 μmol L- 1 and an oxygen saturation reaching 10 % at stations. From a depth of 113 m- Oxygen was no longer detectable at any of the stations. Nutrient data from the upper layer are lacking because they were not interesting for redox processes. Ammonium only increased below 100m depth, nitrate was extremely variable between 50m and 140m experiencing maxima of 6µmol L-1. Finally nitrite had up to 0.4 µmol L-1 around 50m depth and many tiny peaks throughout the redoxzone. The detailed structure visible in the data is unique and will generate a much better understanding of microbial processes and trace metal concentrations.