The paper presents the results of a comparison of water turbidity and suspended particulate matter concentration (SPM) obtained from quasi-synchronous in situ and satellite remote-sensing data. Field measurements from a small boat were performed in April and May 2019, in the northeastern part of the Black Sea, in the mouth area of the Mzymta River. The measuring instruments and methods included a turbidity sensor mounted on a CTD (Conductivity, Temperature, Depth), probe, a portable turbidimeter, water sampling for further laboratory analysis and collecting meteorological information from boat and ground-based weather stations. Remote-sensing methods included turbidity and SPM estimation using the C2RCC (Case 2 Regional Coast Color) and Atmospheric correction for OLI ‘lite’ (ACOLITE) ACOLITE processors that were run on Landsat-8 Operational Land Imager (OLI) and Sentinel-2A/2B Multispectral Instrument (MSI) satellite data. The highest correlation between the satellite SPM and the water sampling SPM for the study area in conditions of spring flooding was achieved using C2RCC, but only for measurements undertaken almost synchronously with satellite imaging because of the high mobility of the Mzymta plume. Within the few hours when all the stations were completed, its boundary could shift considerably. The ACOLITE algorithms overestimated by 1.5 times the water sampling SPM in the low value range up to 15 g/m3. For SPM over 20–25 g/m3, a high correlation was observed both with the in situ measurements and the C2RCC results. It was demonstrated that quantitative turbidity and SPM values retrieved from Landsat-8 OLI and Sentinel-2A/2B MSI data can adequately reflect the real situation even using standard retrieval algorithms, not regional ones, provided the best suited algorithm is selected for the study region.

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The results of field experiments concurrent to satellite surveys conducted in the summer periods of 2014-2019 in the southeastern part of the Baltic Sea off Sambian Peninsula are presented. The main goal was to study coastal currents in a highly variable wind field and its impact on the transport of potential marine pollution. Southeast Baltic is, on the one hand, an area of active navigation, fishing, off-shore oil production, and, on the other hand, a rapidly developing recreation area. It is also an area of frequent massive blooming of harmful algae. Considering these facts, studying coastal currents and their impact on antropogenic and biogenic pollution propagation in the area is highly important. Our main research instrument was drifting Lagrangian buoys (mini-drifters) that are quite often used in oceanography today, Acoustic Doppler Current Profiler (ADCP) and CTD probe measuring temperature, conductivity (salinity) and pressure (depth) and in-situ turbidity and CHL-a In addition, we used satellite remote sensing data publicly available from European and American databases. Mainly, these were data obtained from Sentinel-2 (MSI), Landsat-8 (OLI/TIRS), Sentinel-3 (OLCI) and MODIS (Aqua/Terra) satellites. The experimental data allowed us to describe in detail the alongshore current structure and identify the areas most affected by marine pollution, among which are the most popular places of the region: the beaches of the Yantarniy settlement and Curonian Spit, a national nature reserve and a UNESCO World Heritage Site.

The results of field measurements of coastal currents using Lagrangian mini-drifters are presented. Drifter experiments were conducted concurrently with satellite imaging using Sentinel-2 MSI, Landsat-8 OLI and Sentinel-3 OLCI sensors. It is shown that the use of an inexpensive and simple to manufacture device, which is a mini-drifter, allows obtaining operational information about the parameters of coastal currents. In the experiments of April-May, 2019, in the northeastern part of the Black Sea, it was possible to estimate the velocity of coastal currents and determine the minimum distance that Black Sea Rim Current approached the coast. The trajectories of mini-drifters revealed the manifestations of inertial oscillations whose spatial characteristics are almost impossible to measure in any other way. The influence of the vortex structures detected in visible satellite images on the distribution of mini-drifters was estimated.

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