November 3–11, 2015, 81^st cruise of R/V Professor Vodyanitskiy took place. The expedition was attended by employees of Federal State Budget Scientific Institution "Marine Hydrophysical Institute of the Russian Academy of Sciences" (FSBSI MHI), Federal State Budget Scientific Institution "P.P. Shirshov Institute of Oceanology of RAS" (IO RAS) and Federal State Budget Scientific Institution "Institute of Marine Biological Research of RAS (FSBSI IMBR).

Scientists of the three scientific research institutes of RAS carried out complex monitoring of the western part of the Black Sea within the economic zone of Russia.

Aims of the expedition were as follows

• climate monitoring of the active layer of the Black Sea on the Chersonesus-Bosphorus stack;
• study of the water transformation of cold intermediate layer (CIL) in the autumn period;
• study of hydrological, hydrochemical and biogeochemical properties of sea water in the autumn season of 2015 on the Chersonesus-Bosphorus age stack and in the area of the western cyclonic eddy;
• obtaining experimental data on the vertical distribution of the velocity of currents in the studied areas;
• study of the spatial-temporal variability of the turbidity field (suspended matter concentration) in the studied areas;
• polarographic and geochemical studies;
• sedimentation trap rise monitored on November 17, 2013 by German R/V MARIA S. MERIAN;
• bottom sediment trap installation;
• study of hydrometeorological conditions in the western part of the Black Sea;
• study of the processes of biotic self-purification of the Black Sea water column with respect to pollutants of nuclear and non-nuclear nature;
• study of the effect of hydrophysical and hydrochemical characteristics on the spatial distribution of chlorophyll a, the indicators of the solar energy absorption efficiency by the optically active components of the water column and the quantum yield of the primary processes of photosynthesis.

In 81th of R/V Professor Vodyanitskiy the following scope of works on 17 stations was carried out:

• 53 soundings by hydrologic CTD-probe Sea-Bird’s 911 plus with a cassette of bathometers;
• 17 soundings by acoustic Doppler ADCP Workhorse Monitor 300 kHz current meter;
• 793 analyzes of water samples, including 95 – for dissolved oxygen, 101 – for hydrogen sulfide, 82 measurements each for pH, alkalinity, TCO₂ and pCO₂, 92 measurements of ammonium content, 74 measurements of nitrite content, 29 measurements per suspended substance;
• 74 samples of sea water were collected and frozen for subsequent analysis of nutrients (phosphates, silicates, nitrates);
• 1 vertical column bottom profiling;
• 18 soundings using the Sigma 1 measuring complex in the depth range from 90 to 300 m to collect experimental data on the fine structure and microstructure of the current velocity, temperature and conductivity fields;
• measurements at all stations of hydrometeorological parameters (wind speed and direction, temperature of the atmosphere and water, relative air humidity, atmospheric pressure), cloudiness and wave characteristics (visually);
• 3 measurements of wave characteristics using a sea buoy with an accelerometer sensor;
• 13 measurements of the Secchi disk visibility depth and the sea color on the Forel-Ule color scale;
• water column sounding by a spectral meter of the light attenuation index at all oceanographic stations;
• 5 bottom sampling by means of Okean samplers;
• 3 bottom soil sampling using a multicopper;
• lifting and installing a deepwater sedimentation trap;
• research of atmospheric aerosols (counting concentration, granulometric composition);
• water sampling to determine the content of oil hydrocarbons and phytoplankton pigments, to study microbial processes and the concentration of methane in the water column and bottom sediments;
• 240 measurements of the bioluminescence field by the “Salpa” complex;
• sampling to determine chlorophyll a concentration, light absorption spectra of suspended matter, light absorption spectra of dissolved organic matter, picoplankton abundance indicators, distribution profile of cesium man-made radionuclides (¹³⁷Cs) and strontium (⁹⁰Sr) in the water column of the Black Sea; mercury pollution of sea water; polonium activity (²¹⁰Po).