Dissolved oxygen variability in the southern Baltic Sea in 2013-2018

This paper discusses changes in the dissolved oxygen concentration (DOC) in the southern Baltic Sea. The oxygenation of the whole water column was estimated. Monthly mean DOCs, as well as a detailed description of the annual surface layer dissolved oxygen (DO) cycle, are presented. The DO cycle at the surface is characterized by two maxima in March/April and November, and by two minima in July/August and December. The DO decline time after the major Baltic inflow (MBI) in 2014 was estimated at about 10 months for the Bornholm Deep and Slupsk Furrow. Whereas the Bornholm Basin was relatively well oxygenated, low oxygen concentrations (<4 mg l(-1)) were measured in the deep layer of the Gdansk Deep throughout the inflow period. In addition, the cod spermatozoa activation layer together with the neutral egg buoyancy layer for the Bornholm Basin and Slupsk Furrow are discussed on the basis of the measured DOCs and the variability in hydrographic conditions. (C) 2020 Institute of Oceanology of the Polish Academy of Sciences. Production and hosting by Elsevier B.V.