Temporal and spatial variability of the suspended particulate matter in the Gdansk Deep and Eastern Gotland Basin

The work was carried out in the south-eastern part of the Baltic Sea on the meridional section along the Russian–Polish border during 2015–2018 using the CTD-sounding. The suspended particulate matter samples were taken with the use of ultrafiltration of sea water (0.4 micron filters). The research was focused on identifying the temporal and spatial variability of suspended particulate matter distribution after a series of inflows of the North Sea waters in 2014–2016. The vertical structure of the suspended particulate matter distribution in the south-eastern Baltic, both on a seasonal and interannual scale, contains the main features common for all marine basins, namely increased concentrations of SPM at the sea surface and bottom and an intermediate layer of minimum concentrations located at a depth of 50–70 m. Seasonal fluctuations in the SPM concentration are very significant and are mainly due to the seasonal variation of bioproduction in the surface layer of the sea and the flow of rivers. The confirmation of the barrier role of density boundaries (thermocline and halocline) in sedimentation and geochemical processes has not been obtained.