In this paper, the causes of the anomalous harmful algal bloom which occurred in the fall of 2020 in Kamchatka have been detected and analyzed using a long-term time series of heterogeneous satellite and simulated data with respect to the sea surface height (HYCOM) and temperature (NOAA OISST), chlorophyll-a concentration (MODIS Ocean Color SMI), slick parameters (SENTINEL-1A/B), and suspended matter characteristics (SENTINEL-2A/B, C2RCC algorithm). It has been found that the harmful algal bloom was preceded by temperature anomalies (reaching 6 °C, exceeding the climatic norm by more than three standard deviation intervals) and intensive ocean level variability followed by the generation of vortices, mixing water masses and providing nutrients to the upper photic layer. The harmful algal bloom itself was manifested in an increase in the concentration of chlorophyll-a, its average monthly value for October 2020 (bloom peak) approached 15 mg/m3, exceeding the climatic norm almost four-fold for the region of interest (Avacha Gulf). The zones of accumulation of a large amount of biogenic surfactant films registered in radar satellite imagery correlate well with the local regions of the highest chlorophyll-a concentration. The harmful bloom was influenced by river runoff, which intensively brought mineral and biogenic suspensions into the marine environment (the concentration of total suspended matter within the plume of the Nalycheva River reached 10 mg/m3 and more in 2020), expanding food resources for microalgae.

In this paper, we describe the developed methods and technologies, as well as the created research prototype of a ground-space regional monitoring system that was used for comprehensive experimental research of anthropogenic impact on Russian Black sea coastal water areas. Changes in significant water environment parameters (generation of additional spectral components of surface waves; changes in marine surface roughness affecting normalized radar cross-section; turbidity field anomalies affecting spectral brightness variations in various bands of electromagnetic spectrum, etc.) registered in satellite imagery of water areas under anthropogenic impact were revealed. It has been established that these effects were predominantly caused by deep wastewater discharges. Zones of anthropogenic pollution propagations, as well as pipe breakages, have been revealed. The validation of the obtained satellite imagery processing results has been conducted based on sea truth data carried out using buoys, as well as from boats and hydrophysical platform.

The field of internal waves in the Black Sea is quite significant. The Black Sea shelf is of particular interest, but it has not been studied enough in some specific regions. For example, a narrow and steep shelf of Abkhazia has been poorly explored. Particularly unexplored are the actual parameters and causes of the generation of internal waves in this area. In this article, we have attempted to fill this gap by analyzing remote sensing data and in situ data. An analysis of a set of optical multispectral satellite images (Sentinel-2, Landsat-8) and a collection of sea-truth data of the shelf zone of Abkhazia was carried out to identify features of internal wave fields of this region. In situ data were acquired over 9 years using ADCP, CTD, and SVP probes and moored stations with point and line temperature sensors. It is shown that internal waves are widespread on the Abkhazian shelf. They appear as trains of short-period waves (as a rule, soliton-like). The quantitative parameters and features of internal waves are shown and analyzed. The form of manifestation and direction of internal wave trains’ travel depend on the mechanisms of their origin, among which are the transformations of inertial internal waves, generation by river plumes, and submesoscale structures. In general, the article is the most complete and relevant study of the field of internal waves on the shelf of Abkhazia.

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The results of space monitoring of an extreme ecological situation near Kamchatka Peninsula, which was responsible for a mass death of hydrobionts in autumn 2020, are presented. The analysis of long-term series of satellite data (>15 000 scenes) on sea surface temperature (from 1981 to 2020) and concentration of chlorophyll a (from 2000 to 2020) showed strong positive temperature anomalies (deviations from a climate norm 3–6°C) in the studied region in July–September 2020, which resulted in anomalous increase in the concentration of chlorophyll a (5–8 times higher than the background values) in the end of September–the beginning of October 2020. As a result, a significantly changed biogenic regime led to harmful bloom of algae (red tide), which caused death of hydrobionts both in Avacha Bay and coastal regions of the entire Kamchatka Peninsula.