Spatial distribution of the Black Sea copepod, Calanus euxinus, estimated using multi-frequency acoustic backscatter

The copepod Calanus euxinus is a key prey species for fish in the Black Sea. To estimate the distribution and biomass of the late developmental stages of this species in July 2013, we analysed multi-frequency (38, 120, and 200 kHz) echo-sounder data from a fisheries survey of the Black Sea. The dependence of acoustic backscatter on frequency, i.e. the frequency response, was estimated for daytime scattering layers, which were confirmed by net catches to be dense, post-copepodite-stage (C4) aggregations of C. euxinus with prosome lengths greater than 2 mm. The high-resolution acoustic observations revealed that the nighttime, shallow distribution was bounded by the lower portion of the thermocline and that the daytime, deep distribution was bounded by oxygen. The dense and isolated aggregations were observed in seawater with a specific density, σT, of between 15.2 and 15.9 kg m−3. These results show that fisheries acoustic surveys, typically targeting only commercially exploited fish species, may also provide information on the lower trophic levels and thereby serve as an ecosystem-monitoring tool.

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Temporal variability of the microbial food web (viruses to ciliates) under the influence of the Black Sea Water inflow (N. Aegean, E. Mediterranean)

Mediterranean Marine Science ◽

10.12681/mms.1041 ◽

2014 ◽

Vol 15 (4) ◽

pp. 769 ◽

Cited By ~ 9

Author(s):

A. GIANNAKOUROU ◽

A. TSIOLA ◽

M. KANELLOPOULOU ◽

I. MAGIOPOULOS ◽

I. SIOKOU ◽

...

Keyword(s):

Food Web ◽

Black Sea ◽

Bacterial Production ◽

Heterotrophic Bacteria ◽

Sea Water ◽

Phytoplankton Bloom ◽

Aegean Sea ◽

Trophic Levels ◽

Microbial Food Web ◽

The Black Sea

Τhe entire pelagic microbial food web was studied during the winter-spring period in the frontal area of the North Aegean Sea. Abundance of viruses, heterotrophic bacteria, cyanobacteria, auto- and hetero-trophic flagellates, and ciliates, as well as bacterial production, were measured at three stations (MD1, MD2, MD3) situated along a N-S transect between the area directly influenced by the inflowing Black Sea water and the area covered by the Levantine water. Samples were collected in December 2009, and January, March, April, and May 2011. Station MD1 exhibited the highest values of abundance and integrated biomass of all microbial groups and bacterial production during all months, and MD3 the lowest. Bacteria dominated the total integrated biomass at all stations and months, followed by cyanobacteria, auto-, hetero-trophic flagellates and ciliates. On a temporal scale, the microbial food web was less important in March as all microbial parameters at all stations showed the lowest values. After the phytoplankton bloom in March, the heterotrophic part of the microbial food web (mainly) strongly increased, though the intensity of the phenomenon was diminished from North to South. Pico-sized plankton was found to be heterotrophic whereas nanoplankton was autotrophic. It seems that the influence of the Black Sea water on station MD1, permanent throughout the study period of early winter to late spring, was reflected in all microbial populations studied, and produced a more productive pelagic food web system, with potential consequences for the upper trophic levels.

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Structure of Rapana venosa (Gastropoda, Muricidae) population of Sevastopol bays (the Black Sea)

Marine Biological Journal ◽

10.21072/mbj.2016.01.3.02 ◽

2016 ◽

Vol 1 (3) ◽

pp. 14-21 ◽

Cited By ~ 2

Author(s):

I. P. Bondarev

Keyword(s):

Black Sea ◽

Structural Parameters ◽

Stable Condition ◽

Current Status ◽

The Black Sea ◽

Ecosystem Monitoring ◽

Rapana Venosa ◽

Local Populations ◽

Key Factor ◽

Feeding Resources

Predatory invasive gastropod species Rapana venosa has become an important element of the Black Sea benthic ecosystem. Systematic monitoring of its populations is an important part of benthic ecosystem monitoring in the Black Sea. In this study the population of R. venosa has been investigated at four bays in Sevastopol (Golubaya, Kazach’ya, Kruglaya and Streletskaya) during summer 2015. The main characteristics of R. venosa local populations were determined and compared. Size, weight, sex and age structure of Rapana local populations were studied and compared between these four sites. Current status and possible development of Rapana populations in four bays based on this analysis were accessed. It was found out, that Rapana population in the Kruglaya Bay is in the most stable condition with the most balanced structural parameters. Local populations of R. venosa in other bays are (quasi)stable to varying degrees. Local diet and feeding resources were found to be the key factor influencing the structure and parameters of Rapana populations in Sevastopol bays.

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

10.5194/os-2020-106 ◽

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]

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Annual and Seasonal Variation in Artemia Population in Relation to Water Quality Parameters in Lake Galgas in Crimea, Russia

Asian Journal of Environment & Ecology ◽

10.9734/ajee/2019/v11i230134 ◽

2019 ◽

pp. 1-9

Author(s):

Rudneva Irina Ivanovna ◽

Shaida Valentin Grigor’evich ◽

Sherba Anton Viktorovich ◽

Zav’vyalov Andrei Veniaminovich

Keyword(s):

Oxygen Concentration ◽

Black Sea ◽

Developmental Stages ◽

Quality Parameters ◽

The Black Sea ◽

Hatching Rate ◽

Northern Coast ◽

Hydrochemical Characteristics ◽

Local Climate ◽

Artemia Population

Aim: To study seasonal changes of hydrological parameters of the water and Artemia population status in the hypersaline Galgas Lake in the period of 2017-2019. Study Area and Duration: The study was carried out in the Crimea, a peninsula on the northern coast of the Black Sea in Eastern Europe in 2017-2019. Methodology: Water (brine) and Artemia samples were collected monthly from the lake located at the coastal line of the Black Sea. The parameters namely temperature, pH, salinity, Eh, and oxygen concentration of were determined in the water. Artemia population including the developmental stages and the cysts hatching rate of the cysts were measured in different seasons in the study period. The differences in hydrochemical characteristics of the study area in different years and seasons were observed. Results: The results showed that the hydrochemical characteristics of the study area varied with the climate peculiarities. In summer months 2017, the lake was dried out. In the hot period, the temperature of the air and water was above +30°C, the pH ranged insignificantly, and the oxygen concentration was low. Artemia cysts were found throughout the year, however the nauplii were mostly available during spring and autumn seasons, while the adults were found in spring and summer months. Conclusion: The study concluded that the changes of the water parameters depended on season and especially on air temperature. The changes of Artemia population were different in examined years and depended on the water characteristics and especially on temperature and oxygen concentration. The obtained results could be helpful for the local climate changes consequences studies and their influence on aquatic biota.

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Evaluating trophic cascades as drivers of regime shifts in different ocean ecosystems

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2013.0265 ◽

2015 ◽

Vol 370 (1659) ◽

pp. 20130265 ◽

Cited By ~ 28

Author(s):

Andrew J. Pershing ◽

Katherine E. Mills ◽

Nicholas R. Record ◽

Karen Stamieszkin ◽

Katharine V. Wurtzell ◽

...

Keyword(s):

Baltic Sea ◽

Black Sea ◽

Trophic Cascade ◽

Regime Shifts ◽

Trophic Levels ◽

The Black Sea ◽

Top Down ◽

Scotian Shelf ◽

Bottom Up ◽

Ocean Ecosystems

In ecosystems that are strongly structured by predation, reducing top predator abundance can alter several lower trophic levels—a process known as a trophic cascade. A persistent trophic cascade also fits the definition of a regime shift. Such ‘trophic cascade regime shifts' have been reported in a few pelagic marine systems—notably the Black Sea, Baltic Sea and eastern Scotian Shelf—raising the question of how common this phenomenon is in the marine environment. We provide a general methodology for distinguishing top-down and bottom-up effects and apply this methodology to time series from these three ecosystems. We found evidence for top-down forcing in the Black Sea due primarily to gelatinous zooplankton. Changes in the Baltic Sea are primarily bottom-up, strongly structured by salinity, but top-down forcing related to changes in cod abundance also shapes the ecosystem. Changes in the eastern Scotian Shelf that were originally attributed to declines in groundfish are better explained by changes in stratification. Our review suggests that trophic cascade regime shifts are rare in open ocean ecosystems and that their likelihood increases as the residence time of water in the system increases. Our work challenges the assumption that negative correlation between consecutive trophic levels implies top-down forcing.

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Phytoplankton Growth Rate and Microzooplankton Grazing under Conditions of Climatic Changes and Anthropogenic Pollution in the Coastal Waters of the Black Sea (Sevastopol Region)

Water ◽

10.3390/w13223230 ◽

2021 ◽

Vol 13 (22) ◽

pp. 3230

Author(s):

Lyudmyla Stelmakh ◽

Nelya Kovrigina

Keyword(s):

Growth Rate ◽

Black Sea ◽

Coastal Waters ◽

Phytoplankton Biomass ◽

Trophic Levels ◽

The Black Sea ◽

Anthropogenic Pressure ◽

Diatom Species ◽

Nutrition Quality ◽

Microzooplankton Grazing

In the coastal waters of the Black Sea near Sevastopol, a gradual temperature elevation and an increase in anthropogenic pressure since the early 2000s have caused significant structural and functional changes in phytoplankton. Currently, there is a significant decrease in the contribution of small diatom species (Skeletonema sp. and Chaetoceros socialis H.S.Lauder as well as coccolithophorids Emiliania huxleyi (Lohmann) W.W.Hay and H.P.Mohler) to the total phytoplankton biomass in these waters. Previously these species caused regular weak blooms. In the warm periods (from May to October), during which the main phytoplankton biomass is formed, large diatom species Pseudosolenia calcar-avis (Schultze) B.G.Sundström, 1986, Proboscia alata (Brightwell) Sundström and dinoflagellates predominate. Therefore, the maximum values of the phytoplankton community’s specific growth rate are about two times lower than in the preceding periods and do not exceed 1.10–1.40 day−1. There was also a decrease observed in the microzooplankton grazing rate, which, during the year, was no higher than 0.70–1.20 day−1. This is primarily conditioned by the increased role of large algae in phytoplankton, which means a decline in nutrition quality for microzooplankton. As a result of the joint influence of nutrition quality and water pollution, the relative share of net primary production consumed by microzooplankton in the warm periods of the year averaged only 32%, which is two times lower than the average values generally accepted for marine ecosystems. This means that the transfer of matter and energy from phytoplankton to higher trophic levels is significantly decreased.

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