Abstract
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.
Highlights
Harmful algal blooms are dangerous natural processes which are difficult to be predicted or prevented
The abovementioned features provide for the high efficiency of marine water area remote sensing when solving various thematic tasks related with coastal water area pollution detection, including to study and monitor microalgae blooming [9,10]
Up-to-date scientific publications on the topic of this paper shows that the problem of satellite data application for monitoring and studying harmful algal blooms (HAB) can have different formulations
Summary
Harmful algal blooms are dangerous natural processes which are difficult to be predicted or prevented. Satellite monitoring methods have a wide range of capabilities to study marine water areas which include wide coverage; efficiency; capability to work in any hard-to-reach areas of seas and oceans; obtaining data of various spatial and temporal resolution in different electromagnetic wave spectral regions; a wide range of registered parameters of water environment; and high reliability of obtained data [6]. The efficiency of these methods is largely increased when combining them with sea truth and modeling results [7,8]. The abovementioned features provide for the high efficiency of marine water area remote sensing when solving various thematic tasks related with coastal water area pollution detection, including to study and monitor microalgae blooming [9,10]
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