Using the vertical sounding method for recording bioluminescence in the antarctic sector of the Atlantic Ocean

Abstract

Bioluminescence is a significant element in the functioning of the pelagic community. The glow of marine aquatic organisms is a manifestation of their vital activity in the form of electromagnetic radiation in the visible area of the spectrum, the kinetic patterns of which are closely related to the mechanism generating their chemical reactions and metabolic processes. Global warming, which undoubtedly has affected the Antarctic sector of the Atlantic Ocean, caused serious structural and functional changes in the pelagic community with repercussion on marine bioluminescence, which is an expressive indicator of the state of the environment. The objective of the study was to demonstrate that the method of multiple vertical soundings by the hydro-biophysical complex Salpa-M, with the simultaneous capture of biophysical and hydrological parameters at one station, is effective enough in studying the structure and length of the glow fields of Antarctic waters. The idea of the sounding method is raising (or lowering) the Salpa-M bathyphotometer at a constant speed in a given layer (usually this is the upper productive one of 0-200 m or the photic layer of 0-100 m) in the vessel's drift. Planktonic bioluminescent substances, which make the main contribution to the formation of the bioluminescent potential of the pelagial, illuminate, as a rule, only when agitated; therefore, a bathyphotometer moving at a constant speed creates a standard level of mechanical agitation of bioluminescent bodies, which makes it possible to correctly compare the results of measurements of the vertical structure of the bioluminescence field carried out in different regions and under various weather conditions (rocking, wind drift, etc.). The paper presents materials and methods for studying the structural characteristics of bioluminescence obtained during the 79th Antarctic expedition onboard R/V Academician Mstislav Keldysh. The paper considers an important issue related to the change in the bioluminescence of seawater in the Atlantic sector of the Antarctic Ocean studied by the method of vertical sounding at different levels using a bioluminescent probe. This information is important for further understanding the global climate/anthropogenic impacts on the marine ecosystem. The paper presents a fairly large data set of the integral bioluminescent signal at different horizons. Primary data on bioluminescence intensity, temperature values, electrical conductivity and photosynthetically active radiation were obtained at 18 hydrographic stations in the studied water area of the Antarctic sector of the Atlantic Ocean. In the study of bioluminescence, the vertical variability of the glow in the upper productive layer was determined due to the peculiarities of the plankton distribution. As a result, it was found out that the glow of Antarctic waters in the photic layer of this area occurs within the range of 8,4^-12 W·cm^-2·l^-1 to 104,42^-12 W·cm^-2·l^-1. Bioluminescence peaks (up to 104^-12 W·cm^-2·l^-1) were recorded under the thermocline at a depth of 45 m in the zones of salp Salpa thompsoni Foxton, 1961  concentration near the hydrological front at a distance of about 6-7 miles on both sides of it. As a result, it was shown that thanks to the use of the method of vertical sounding in Antarctic waters, there is an express possibility to register the fields and structure of the accumulation of luminous organisms. Taking into account the practical significance of the study, the relevance of the study is not subject to doubt.

Keywords: bioluminescence intensity, Atlantic sector of Antarctica, euphotic zone, vertical sensing, plankton