ISSN 0097-8078, Water Resources, 2016, Vol. 43, No. 1, pp. 33–41. © Pleiades Publishing, Ltd., 2016. Original Russian Text © V.A. Chechko, V.Yu. Topchaya, B.V. Chubarenko, V.A. Pilipchuk, 2016, published in Vodnye Resursy, 2016, Vol. 43, No. 1, pp. 37–46. 33 INTRODUCTION Suspended matter (SM), an important geochemi- cal and ecological characteristic of the state of any aquatic ecosystem, has a considerable effect on water properties. The knowledge of SM dynamics makes it possible to identify the directions of propagation of passive material of anthropogenic genesis and to answer the questions regarding the current sedimenta- tion process [1, 8, 16–18, 20, 22, 32, 34]. The general regularities of the quantitative distribution of SM and its material and granulometric composition in Kalin- ingrad Bay have been studied in detail [2, 3, 25, 26]. As shown in [14, 24, 28, 31, 37], the key factors that determine the space and time variations of SM are wind and wave roiling of bottom sediments, river run- off, biological production, abrasion–erosion pro- cesses, and surging. The directions of transport and the zones of precipitation of polluted particulate mat- ter [4] and the major sources of anthropogenic roiling [30, 39] were determined. It is worth mentioning, however, that the studies were carried out in spring and autumn (ice-free) peri- ods, though the bay is a freezing water body with a mean duration of freeze-up period of 117 and its max- imal duration of 140 days [9]. Considering that ice cover protects the water mass from wind–wave impact for several months and in a natural manner changes the values of other factors, we come to an obvious con- clusion that the seasonal variations of the quantitative characteristics, material composition, and SM dynamics in the bay cannot be assessed reliably unless the freeze-up period is taken into account. Moreover, studying the snow cover on the ice of the bay enables the studying of the least known SM source—eolian process. In this study, the results of field measurements are analyzed to reveal the regularities of SM distribution and composition under freeze-up conditions and to identify the main factors underlying these regularities; an attempt is also made to estimate the eolian material entering the bay water area in winter. THE OBJECT AND METHODS OF STUDY Kaliningrad Bay is the official name of the Russian part of Vistula Lagoon—a major shallow (its maximal depth is 5.2, and mean depth is 2.7 m) basin of lagoon type in the Baltic Sea. Vistula Lagoon is situated in the southeastern part of the Baltic Sea (Fig. 1). This is a transboundary water body with a water area of 838 km 2 , of which 570 km 2 is the Russian part (Kali- ningrad Bay). The lagoon is separated from the sea by a sand spit, and water exchange with the sea takes place through the navigable Baltic Strait. The eastern part of the lagoon receives the Pregel R., the most abundant river in the lagoon basin, which shows low velocities of surface currents (on the average, 6–7 cm/s at its mouth) and supplies ~82% of SM delivered into the lagoon by total river runoff [9, 25, 27]. Kaliningrad Bay is an object of active economic development. The Kaliningrad Sea Canal (KSC) with year-round navigation and port complexes and oil ter- minals on its banks passes along its northern shore; fishery and sand and gravel extraction are carried out in the bay water area; the recreation significance of the bay has also increased in the recent years. No doubt, Distribution and Composition of Suspended Matter in Water and Snow Cover in Kaliningrad Bay V. A. Chechko, V. Yu. Topchaya, B. V. Chubarenko, and V. A. Pilipchuk Atlantic Branch, Shirshov Institute of Oceanology, Russian Academy of Sciences, prosp. Mira 1, Kaliningrad, 236022 Russia E-mail: che-chko@mail.ru Received July 31, 2014 Abstract—Field data, collected by the authors during winter expedition studies in Kaliningrad Bay, are ana- lyzed. Notwithstanding the presence of ice cover, considerable advective processes are shown to be taking place in the bay. Seawater enters the bay, spreading in the bottom horizon all over the water area. Suspended sediment concentration in under-ice period is on the average three times less than that in the ice-free period. The space and time variations of its quantitative and qualitative composition under ice are mostly governed by two factors—the effect of the sea and river runoff. The values of vertical fluxed of eolian material to the bay surface in winter vary from 0.5 to 2.9 with the average of 1.7 mg m –2 day –1 . Keywords: ice cover, water salinity, suspended sediments, sedimentation, eolian material DOI: 10.1134/S009780781601005X WATER RESOURCES AND THE REGIME OF WATER BODIES