scholarly journals Seasonal variation of the sound-scattering zooplankton vertical distribution in the oxygen-deficient waters of the NE Black Sea

Ocean Science ◽  
2021 ◽  
Vol 17 (4) ◽  
pp. 953-974
Author(s):  
Alexander G. Ostrovskii ◽  
Elena G. Arashkevich ◽  
Vladimir A. Solovyev ◽  
Dmitry A. Shvoev
Keyword(s):  
Vertical Distribution ◽  
Black Sea ◽  
Acoustic Backscatter ◽  
Sound Scattering ◽  
Hypoxic Zone ◽  
Acoustic Beams ◽  
Oxic Zone ◽  
Sound Scattering Layer ◽  
The Vertical Distribution ◽  
Temperature Depth

Abstract. At the northeastern Black Sea research site, observations from 2010–2020 allowed us to study the dynamics and evolution of the vertical distribution of mesozooplankton in oxygen-deficient conditions via analysis of sound-scattering layers associated with dominant zooplankton aggregations. The data were obtained with profiler mooring and zooplankton net sampling. The profiler was equipped with an acoustic Doppler current meter, a conductivity–temperature–depth probe, and fast sensors for the concentration of dissolved oxygen [O2]. The acoustic instrument conducted ultrasound (2 MHz) backscatter measurements at three angles while being carried by the profiler through the oxic zone. For the lower part of the oxycline and the hypoxic zone, the normalized data of three acoustic beams (directional acoustic backscatter ratios, R) indicated sound-scattering mesozooplankton aggregations, which were defined by zooplankton taxonomic and quantitative characteristics based on stratified net sampling at the mooring site. The time series of ∼ 14 000 R profiles as a function of [O2] at depths where [O2] < 200 µm were analyzed to determine month-to-month variations of the sound-scattering layers. From spring to early autumn, there were two sound-scattering maxima corresponding to (1) daytime aggregations, mainly formed by diel-vertical-migrating copepods Calanus euxinus and Pseudocalanus elongatus and chaetognaths Parasagitta setosa, usually at [O2] = 15–100 µm, and (2) a persistent monospecific layer of the diapausing fifth copepodite stages of C. euxinus in the suboxic zone at 3 µm < [O2] < 10 µm. From late autumn to early winter, no persistent deep sound-scattering layer was observed. At the end of winter, the acoustic backscatter was basically uniform in the lower part of the oxycline and the hypoxic zone. The assessment of the seasonal variability of the sound-scattering mesozooplankton layers is important for understanding biogeochemical processes in oxygen-deficient waters.

scholarly journals Annual cycle of sound-scattering mesoplankton in the oxycline and hypoxic zone in the northeastern Black Sea

2020 ◽  
Author(s):  
Alexander G. Ostrovskii ◽  
Vladimir A. Solovyev ◽  
Dmitry A. Shvoev
Keyword(s):  
Black Sea ◽  
Annual Cycle ◽  
Bottom Layer ◽  
Acoustic Backscatter ◽  
The Black Sea ◽  
Sound Scattering ◽  
Near Surface ◽  
Hypoxic Zone ◽  
Acoustic Beams ◽  
Temperature Depth

Abstract. To investigate the annual cycle of sound-scattering layers in the Black Sea, a moored profiler equipped with an acoustic Doppler current meter, a conductivity-temperature-depth probe, and fast sensors for dissolved oxygen [O2] was employed. Approximately 13,350 multiparameter profiles from the near-surface layer down to the near-bottom layer were obtained at intervals of 1–2 h from 2013–2020. The acoustic system allowed for observations of ultrasound backscattering at 3 angles at 2 MHz frequency. Combinations of the volume strength data of the 3 acoustic beams (directional acoustic backscatter ratios, R) were found to be a useful tool for visualizing acoustic backscatter patterns associated with mesoplankton in the oxycline and hypoxic zone. The time series of R as a function of [O2] at depths where [O2]

scholarly journals Effects of fluctuating hypoxia on benthic oxygen consumption in the Black Sea (Crimean shelf)

2015 ◽  
Vol 12 (16) ◽  
pp. 5075-5092 ◽  
Author(s):  
A. Lichtschlag ◽  
D. Donis ◽  
F. Janssen ◽  
G. L. Jessen ◽  
M. Holtappels ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Black Sea ◽  
The Black Sea ◽  
Minor Role ◽  
Hypoxic Conditions ◽  
Hypoxic Zone ◽  
Oxic Zone ◽  
A Minor ◽  
Oxygen Concentrations

Abstract. The outer western Crimean shelf of the Black Sea is a natural laboratory to investigate effects of stable oxic versus varying hypoxic conditions on seafloor biogeochemical processes and benthic community structure. Bottom-water oxygen concentrations ranged from normoxic (175 μmol O2 L−1) and hypoxic (< 63 μmol O2 L−1) or even anoxic/sulfidic conditions within a few kilometers' distance. Variations in oxygen concentrations between 160 and 10 μmol L−1 even occurred within hours close to the chemocline at 134 m water depth. Total oxygen uptake, including diffusive as well as fauna-mediated oxygen consumption, decreased from 15 mmol m−2 d−1 on average in the oxic zone, to 7 mmol m−2 d−1 on average in the hypoxic zone, correlating with changes in macrobenthos composition. Benthic diffusive oxygen uptake rates, comprising respiration of microorganisms and small meiofauna, were similar in oxic and hypoxic zones (on average 4.5 mmol m−2 d−1), but declined to 1.3 mmol m−2 d−1 in bottom waters with oxygen concentrations below 20 μmol L−1. Measurements and modeling of porewater profiles indicated that reoxidation of reduced compounds played only a minor role in diffusive oxygen uptake under the different oxygen conditions, leaving the major fraction to aerobic degradation of organic carbon. Remineralization efficiency decreased from nearly 100 % in the oxic zone, to 50 % in the oxic–hypoxic zone, to 10 % in the hypoxic–anoxic zone. Overall, the faunal remineralization rate was more important, but also more influenced by fluctuating oxygen concentrations, than microbial and geochemical oxidation processes.

The Role of Abiotic Environmental Factors in the Vertical Distribution of Macrozoobenthos at the Northeastern Black Sea Coast

2020 ◽  
Vol 47 (9) ◽  
pp. 1126-1141
Author(s):  
G. A. Kolyuchkina ◽  
V. L. Syomin ◽  
K. S. Grigorenko ◽  
A. B. Basin ◽  
I. V. Lyubimov
Keyword(s):  
Environmental Factors ◽  
Vertical Distribution ◽  
Black Sea ◽  
Black Sea Coast ◽  
The Vertical Distribution ◽  
Sea Coast ◽  
Abiotic Environmental Factors

Vertical distribution of the sound-scattering layer in the Amundsen Sea, Antarctica

Polar Science ◽  
2018 ◽  
Vol 15 ◽  
pp. 55-61 ◽  
Author(s):  
Hyungbeen Lee ◽  
Hyoung Sul La ◽  
Donhyug Kang ◽  
SangHoon Lee
Keyword(s):  
Vertical Distribution ◽  
Scattering Layer ◽  
Sound Scattering ◽  
Amundsen Sea ◽  
Sound Scattering Layer

scholarly journals ANALYSIS OF THE THERMOHALINE STRUCTURE IN THE ACTIVE LAYER OF THE MARINE ENVIRONMENT ACCORDING TO THE CALCULATED HYDROPHYSICAL CHARACTERISTICS BASED ON REMOTE MEASUREMENTS (ON THE EXAMPLE OF THE BLACK SEA)

2021 ◽  
Author(s):  
Andrii Sryberko ◽  
Keyword(s):  
Spatial Distribution ◽  
Vertical Distribution ◽  
Water Temperature ◽  
Active Layer ◽  
Black Sea ◽  
Marine Environment ◽  
The State ◽  
The Black Sea ◽  
Thermohaline Structure ◽  
The Vertical Distribution

Today, one of the priority scientific directions in marine sciences is the study of the spatial distribution of hydrophysical characteristics in the marine environment by remote measurements methods. To studying the spatio-temporal variability of water temperature and salinity in the active layer of the marine environment, it is necessary to use the data of their vertical and spatial distribution. Today there does not exist an easy way to get a in situ data for the analysis of the thermohaline structure in the marine environment. Indirect definitions of the vertical and spatial distribution of water temperature and salinity through the development of various methods for the calculation of thermohaline characteristics are used to date. Main purpose of this work is to study the thermohaline structure in the active layer of the Black Sea according to the calculated hydrophysical characteristics based on satellite and hydroacoustic data. The study of the vertical distribution of water temperature and salinity in the Black Sea was carried out in the deep-water part sea at standard levels (0, 10, 20, 25, 30, 50 meters) in the spring –autumn period. This area of research is represented by the highest number of measurements and is included in the Main Black Sea current zone. The calculations of thermohaline characteristics in the marine environment are based on the original methods of calculating the vertical distribution of water temperature, sound speed and salinity of water by satellite and hydroacoustic data. These methods were developed in the State Institute “Hydroacoustic Branch of Institute of Geophysics by S.I. Subbotin name of the National Academy of Sciences of Ukraine”. Mathematical and physical-statistical methods of calculation were used in the developed methods. For the efficiency of calculations an Automated Program Complex (APC) for calculating the vertical distribution of temperature and salinity fields in the marine environment by satellite and hydroacoustic data has been developed and tested on the example of the Black Sea. The initial data for the calculations using the APC are only daily satellite data of the sea surface temperature. Based on the results of calculations of the APC, maps of the vertical distribution of temperature and salinity of water on zonal and meridional sections in the Black Sea in the period of spring – autumn 2018 were developed. Analysis of the results of calculations of the vertical distribution of thermohaline characteristics made it possible to identify the main features in these distributions. The features of the spatial-temporal distribution of thermohaline parameters have been analysed. The confirmation of the state of the thermohaline regime inherent in the Black Sea in the warm season was obtained. The results of calculations of the vertical distribution of thermohaline characteristics in the Black Sea deep-water area on the basis of satellite and hydroacoustic data using the developed methods showed the possibility and expediency of their application in the layer 0-50 meters in the period May-October for a detailed analysis of the state of the thermohaline structure. The developed methods and principles of building an the APC for calculation of vertical distribution of temperature and salinity fields of water according to satellite and hydroacoustic data can be applied for analysis and monitoring of others water area of the World Ocean taking into account their hydrological conditions.

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