In this work, IBSS materials on seawater bioluminescence intensity changes in the Atlantic sector of the Antarctic Ocean (the Weddell Sea area) with an interval of almost 20 years are presented. Data were obtained using a single instrument, the hydrobiophysical system Salpa‐M, in the area of 50–63°S, 62–49°W in March 2002 (183 soundings at 45 stations during cruise 7 on RV Gorizont) and in February 2020 (122 soundings at 18 stations during cruise 79 on RV Academic Mstislav Keldysh). The bioluminescence studies were coupled with the simultaneous measurement of temperature, electrical conductivity, and photosynthetically active radiation, and they were compared with the data from processing plankton samples. Over the past 20 years, as a consequence of the appearance of a large number of gelatinous organisms and the resulting changes in the structure of the plankton community, the bioluminescence of Antarctic waters in the euphotic layer of this region has decreased almost two‐fold, currently being in the range 8.4 × 10−12 to 104.42 × 10−12 W·cm−2·L−1.
Vertical distribution of ctenophores near the boundary of oxygen-depleted waters of the Black Sea redoxcline was studied by use of video observations with real-time water sampling, horizontal MultiNet towing, and soundings using bathyphotometers with simultaneous vertical plankton net sampling. The results of the study showed for the first time that the daytime accumulation of ctenophores above the upper boundary of the suboxic zone changes the biophysical properties of the medium, causing an increase in the daytime intensity of bioluminescence near the redoxcline.The dynamics of this glow is in antiphase to that in the surface layers, where it is associated with the bioluminescence of phytoplankton. Therefore, in the deep-sea areas, two types of bioluminescence peaks differ in the light generation sources: the nighttime glow of phytoplankton in surface layers and the daytime glow of zooplankton in layers of oxygen-depleted waters at the redoxcline. The discovery of this new phenomenon allows the use of bioluminescent methods for the rapid assessment of the depth of the daytime zooplankton layers for the subsequent hauls of plankton nets. This significantly expands the possibilities of studying the structure and functioning of the pelagic ecosystem of the Black Sea and other marine basins with a redoxcline.
In the second half of the XX century, Black Sea ecosystem has undergone significant changes: a number of storm winds and upwellings decreased, precipitation abundance increased, coastal waters salinity decreased, temperature increased; moreover, ctenophores invaded. As a result, in the late 1980s, Black Sea pelagic ecosystem abruptly got restructured. This research is based on the studies performed in 1965–1966 and 2007–2012 near Sevastopol (Western Crimea) using the remote sensing data. Analysis of satellite data over the past 20 years showed the presence of positive dynamics in surface water temperature in Sevastopol water area. In the mid-1960s, the annual bioluminescence was characterized by seasonal peaks of dinophytes luminescence. In recent years, this rhythm has changed due to ctenophores invasion. The increase in Mnemiopsis leidyi abundance leads to a decrease in bioluminescence of luminous microalgae being consumed by these ctenophores. Due to Beroe ovata invasion and reproduction, M. leidyi biomass decreased; as a result, bioluminescence increased.
Global warming, which certainly covered the Black Sea, caused serious structural and functional changes in the pelagic community, effecting marine bioluminescence, which is an expressive indicator of the environment state. A large number of intensely luminescent warm-water ctenophores-invaders appeared in the surface layer, which increased the total plankton luminescence. Their contribution to the total luminosity of the coastal waters has been poorly studied so far. In practical terms, it resulted in changing of unmasking luminosity of any moving objects in the water column. On the other hand, developing of more sensitive methods for monitoring changes in the marine environment state has become possible.
In January 2022, during scientific cruise 87 on the RV Academic Mstislav Keldysh in the Atlantic sector of the Southern Ocean, three hydrobiophysical cross‐sections were performed in the Bransfield Strait. Bioluminescent signals were measured in a layer of 0–200 m at each of the 24 stations located at three sites. For the first time, a new hydrobiological system ‘Salpa MA +’ was used, which made it possible to obtain novel data in the photic layer of the studied water area. Bioluminescence studies were accompanied by simultaneous measurements of background indicators: temperature, electrical conductivity, photosynthetically active radiation, and they were compared with the data from plankton samples processing. Bioluminescent potential was registered at almost all the stations. The maximum level of bioluminescence was registered in the area of the archipelago of the South Shetland Islands, where the maximum accumulation of Salpa thompsoni, Foxton 1861 was noted. The purpose of this work is to identify the main factors and patterns affecting the intensity of the bioluminescence field in the region under study.
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