LAUSR

Early diagenetic transformations of bottom sediments begin upon the sedimentation of dispersed sedimentary matter and involve diverse processes of sediment consolidation, decrease in its water content, transformations of its mineralogy and chemistry, and changes in its organic matter (OM), which controls the physicochemical processes (Strakhov, 1953). In the subarctic White Sea, sedimentation proceeds when the sea covered with ice for a long time, the water temperature is low, and the hydrodynamics is active and related to semidaily tidal oscillations of the sea level (Nevessky et al., 1977; White Sea System, 2012, 2013). Sedimentary matter is irregularly distributed over the seafloor surface: the annual average f luxes of sedimentary matter are at a maximum (2758 g m–2) in the frontal parts (Gorlo of the sea and the Solovetsky Islands) and at a minimum (51 g m–2) in the central part (Lisitzyn et al., 2014). In the central part of the sea, the annual average f luxes of sedimentary matter do not exceed 100 g m–2 (Lisitzyn et al., 2014), and sedimentary matter collected by sediment traps from the near-bottom layer is dominated by abiogenic components: quartz (29%), clay minerals (30%), feldspars and carbonates (15%), and 26% organic matter (Novigatsky et al., 2013). In the uppermost sediment layer, which is in contact with bottom water, biogeochemical processes with the participation of heterotrophs and autotrophs are the most intense (Savvichev et al., 2008). Reductive diagenetic processes, which start to operate in the outermost layer of pelitic muds in the central part of the White Sea (Gursky, 2005), reduce the concentrations of mobile forms of Fe and Mn with depth (Rozanov et al., 2006, 2009). Reduced sulfur species as derivatives of bacterial hydrogen sulfide are precipitated already in the upper layers of the sediments, and their contents increase with depth (Volkov et al., 2003; Rozanov et al., 2006).