Features of the distribution of hydrological, chemical and biological characteristics in the waters of the Central-East Atlantic in the autumn of 2022 (cruise 63 of the R/V «Akademik Ioffe»)

Abstract

The goal of the work : to determine the water structure in the Central part of East Atlantic and to identify the features of the distribution of hydrological, chemical and biological characteristics of the upper layer in the autumn period Materials and methods: the data presented in the work were obtained on the 63rd cruise of the R/V «Akademik Ioffe» (September 29, 2022–December 8, 2022). During the expedition, hydrological and chemical (temperature, salinity, pH, dissolved oxygen, phosphates, nitrites, nitrates and silicates) characteristics were measured from the surface to the bottom, as well as biological (number, biomass and species diversity of phytoplankton), taken with chemical samples on depths of 0, 10, 20 and 50 m. Chemical analysis was carried out in the ship’s laboratory, according to certified methods for sea and fresh waters. Phytoplankton samples were thickenedusing a reverse filtration funnel through track (nuclear) membranes and fixed with Lugol’s solution to a final concentration of 5%. To study the species diversity, abundance and biomass of plankton microalgae, samples were processed by direct microscopy of algae in a living and thickened drop (V = 0.01 ml), as well as in a counting chamber (V = 0.5 ml) using an Olympus CX43 light microscope (magnification 10×20, 10×40). Identification of taxonomic groups and species composition of microalgae, calculations of the abundance and biomass of phytoplankton, as well as the Sörensen-Czekanowski floristic similarity coefficient according to the adoption of the methods of the « IBSS RAS» were carried out. The practical significance of the research : assessment of the production stock in a poorly studied region of the Central Eastern Caucasus, identification of mechanisms for influencing production processes, assessment of the variability of the water structure against the background of climate change.