803 ISSN 0001-4370, Oceanology, 2019, Vol. 59, No. 5, pp. 803–805. © Pleiades Publishing, Inc., 2019. Russian Text © The Author(s), 2019, published in Okeanologiya, 2019, Vol. 59, No. 5. Complex Studies in the 44th Cruise of R/V Akademik Boris Petrov A. V. Krek a , V. T. Paka a , E. V. Krek a, *, E. E. Ezhova a , D. V. Dorokhov a , A. A. Kondrashov a , E. S. Bubnova a , E. P. Ponomarenko a , L. D. Bashirova a , and M. V. Kapustina a a Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia *e-mail: elenka_krek@mail.ru Received December 27, 2018; revised January 25, 2019; accepted February 5, 2019 Abstract—The 44th cruise of R/V Akademik Boris Petrov was carried out from October 5 to 30, 2018 in the Baltic Sea and Skagerrak Strait. The studies included investigation of the water column structure, bottom cur- rents, bottom sediments, and biological communities. Keywords: Baltic Sea, CTD sounding, side-scanning sonar, bottom sediments, plankton communities, benthos DOI: 10.1134/S0001437019050102 The complex studies in the Baltic Sea and Skagerrak Strait, according to the program for monitoring the spa- tio-temporal changes of the Baltic Sea ecosystem, works on the problem of dumped chemical munitions (CM) within the international project DAIMON, as well as introduction of advanced methods for measur- ing the structure and dynamics of water, including a thin bottom layer (October 5–30, 2018) have been car- ried out during the 44th cruise of R/V Akademik Boris Petrov (Fig. 1). Kaliningrad was the port of departure and entrance for the vessel. The hydrophysical research included installation of two long-term bottom stations equipped with measur- ers of currents Aanderaa RCM9 prepared within the project DAIMON in the areas of CW dumping in the Skagerrak Strait and in the Bornholm Deep. The detailed analysis of the water column structure from the surface to the bottom was performed over the long transect (Fig. 1) along the route of the inflows of the North Sea waters (a total of 378 soundings) and on 12 key sections. Work on the transects was carried out during continuous operation of the vessel according to a new technique developed at the Atlantic Branch of the Institute of Oceanology, Russian Academy of Sci- ences, using Sea&Sun CTD-48Mc, with representa- tives of the Sea&Sun in the cruise. The studies on the key stations were complex. The water sampling with the “Rosette” system was accompanied by measure- ments by an Idronaut 316 multi-parametric probe and acoustic profiling of current velocity by the RDI ADCP Workhorse instrument provided by the Atlant- NIRO, which also sent its representative to the cruise. In addition to the development of a new technique for measuring along transects, inclinometric current measurers developed and constructed at the Atlantic Branch of the Institute of Oceanology, Russian Acad- emy of Sciences, were successfully tested in the cruise. These inexpensive and easy-to-use instruments are designed to study the temporal variability and spatial structure of currents in a thin near-bottom layer, inac- cessible to most standard recorders and profilographs. Successful tests were performed both under the condi- tions of predicted minimum current velocities (less than 5 cm/s) and in the conditions of fast density cur- rent in the inflow channel towards the Gotland Deep, which intensified during the storm up to 45 cm/s. The geoacoustic studies included areal survey by a Teledyne Benthos C3D side-scanning sonar (SSS) on the acoustic polygons (Fig. 1) and echo-sounding (Simrad EA400SP) on the polygons and passing tacks. A total of 425 km of continuous SSS survey and 663 km of echo sounding profiling have been performed. The geological works were aimed on sampling of surface sediments using a Van Veen grab (44 samples) for interpretation of the sonar data and sampling of the cores of bottom sediments using a gravity corer of large diameter (one core) and a sealed Niemisto Corer (10 cores) for further study of paleoclimatic and sedi- mentation conditions in the basins of the Baltic Sea, including those under the influence of North Sea inflows and atmospheric circulation over the North- East Atlantic Ocean. The hydrobiological works included the sampling of phyto-, zoo-, and ichthyoplankton, macro- and meio- benthos, as well as water for analysis of the concentra- tion of the forms of nitrogen, phosphorus, and silicon. Water sampling for hydrochemistry and phytoplank- ton was performed at predetermined horizons with 5- or 10-l Niskin bottles installed in the Hydrobios MWS 12 Slimline hydrological complex. The samples of benthos were collected with a Van Veen grab (63 samples of macrozoobenthos and 35 samples of INFORMATION