scholarly journals Spatio-temporal variations of lateral and atmospheric carbon fluxes from the Danube Delta

2020 ◽  
Author(s):  
Marie-Sophie Maier ◽  
Cristian R. Teodoru ◽  
Bernhard Wehrli
Keyword(s):  
Surface Area ◽  
Black Sea ◽  
Carbon Emissions ◽  
Danube River ◽  
The Black Sea ◽  
Danube Delta ◽  
Carbon Turnover ◽  
Carbon Yield ◽  
River Deltas ◽  
Net Export

Abstract. River deltas with their mosaic of ponds, channels and seasonally inundated areas act as the last continental hotspots of carbon turnover along the land-ocean aquatic continuum. There is increasing evidence for the important role of riparian wetlands in the transformation and emission of terrestrial carbon to the atmosphere. The considerable spatial heterogeneity of river deltas, however, forms a major obstacle for quantifying carbon emissions and their seasonality. While river reaches crossing the delta can serve as reference systems, delta lakes are often dominated by aquatic production and channels act as collection systems for carbon exported from adjacent wetlands. In order to quantify carbon turnover and emissions in the complex mosaic of the Danube Delta, we conducted monthly field campaigns over two years at 19 sites spanning river reaches, channels and lakes. Here we report greenhouse gas fluxes (CO2 and CH4) from the freshwater systems of the Danube Delta and present the first seasonally resolved estimates of its freshwater carbon emissions to the atmosphere. Furthermore, we quantify the lateral carbon transport of the Danube River to the Black Sea. We estimate the delta’s CO2 and CH4 emissions to be 65 GgC yr−1, of which about 8 % are released as CH4. The median CO2 fluxes from river branches, channels and lakes are 25, 93 and 5.8 mmol m−2 yr−1, respectively. Median total CH4 fluxes amount to 0.42, 2.0 and 1.5 mmol m−2 yr−1. While lakes do have the potential to act as CO2 sinks in summer, they are generally the largest emitters of CH4. Small channels showed the largest range in emissions including a CO2 and CH4 hotspot sustained by adjacent wetlands. The channels thereby contribute disproportionately to the delta’s emissions considering their limited surface area. In terms of lateral export, we estimate the net export of the Danube Delta to the Black Sea to about 160 GgC yr−1, which only marginally increases the carbon load from the upstream river catchment (8490 GgC yr−1) by about 2 %. While this contribution of the delta seems small, deltaic carbon yield (45.6 gC m−2 yr−1, net export load/surface area) is about 4-fold higher than the riverine carbon yield from the catchment (10.6 gC m−2 yr−1).

scholarly journals Spatio-temporal variations in lateral and atmospheric carbon fluxes from the Danube Delta

2021 ◽  
Vol 18 (4) ◽  
pp. 1417-1437
Author(s):  
Marie-Sophie Maier ◽  
Cristian R. Teodoru ◽  
Bernhard Wehrli
Keyword(s):  
Organic Carbon ◽  
Surface Area ◽  
Black Sea ◽  
Carbon Emissions ◽  
Danube River ◽  
The Black Sea ◽  
Danube Delta ◽  
Carbon Turnover ◽  
Carbon Yield ◽  
River Deltas

Abstract. River deltas, with their mosaic of ponds, channels and seasonally inundated areas, act as the last continental hot spots of carbon turnover along the land–ocean aquatic continuum. There is increasing evidence for the important role of riparian wetlands in the transformation and emission of terrestrial carbon to the atmosphere. The considerable spatial heterogeneity of river deltas, however, forms a major obstacle for quantifying carbon emissions and their seasonality. The water chemistry in the river reaches is defined by the upstream catchment, whereas delta lakes and channels are dominated by local processes such as aquatic primary production, respiration or lateral exchange with the wetlands. In order to quantify carbon turnover and emissions in the complex mosaic of the Danube Delta, we conducted monthly field campaigns over 2 years at 19 sites spanning river reaches, channels and lakes. Here we report on the greenhouse gas fluxes (CO2 and CH4) from the freshwater systems of the Danube Delta and present the first seasonally resolved estimates of its freshwater carbon emissions to the atmosphere. Furthermore, we quantify the lateral carbon transport of the Danube River to the Black Sea. We estimate the delta's CO2 and CH4 emissions to be 65 GgC yr−1 (30–120 GgC yr−1, a range calculated using 25 to 75 percentiles of observed fluxes), of which about 8 % are released as CH4. The median CO2 fluxes from river branches, channels and lakes are 25, 93 and 5.8 mmol m−2 d−1, respectively. Median total CH4 fluxes amount to 0.42, 2.0 and 1.5 mmol m−2 d−1. While lakes do have the potential to act as CO2 sinks in summer, they are generally the largest emitters of CH4. Small channels showed the largest range in emissions, including a CO2 and CH4 hot spot sustained by adjacent wetlands. Thereby, the channels contribute disproportionately to the delta's emissions, considering their limited surface area. In terms of lateral export, we estimate the net total export (the sum of dissolved inorganic carbon, DIC, dissolved organic carbon, DOC, and particulate organic carbon, POC) from the Danube Delta to the Black Sea to be about 160 ± 280 GgC yr−1, which only marginally increases the carbon load from the upstream river catchment (8490 ± 240 GgC yr−1) by about 2 %. While this contribution from the delta seems small, deltaic carbon yield (45.6 gC m−2 yr−1; net export load/surface area) is about 4 times higher than the riverine carbon yield from the catchment (10.6 gC m−2 yr−1).

scholarly journals Sedimentary microplastic concentrations from the Romanian Danube River to the Black Sea

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iulian Pojar ◽  
Adrian Stănică ◽  
Friederike Stock ◽  
Christian Kochleus ◽  
Michael Schultz ◽  
...  
Keyword(s):  
Black Sea ◽  
Danube River ◽  
The Black Sea ◽  
Danube Delta ◽  
Black Sea Coast ◽  
River Danube ◽  
Terrestrial Environments ◽  
Ultimate Fate ◽  
First Time ◽  
Sea Coast

AbstractA multitude of recent studies have detailed microplastic concentrations in aquatic and terrestrial environments, although questions remain over their ultimate fate. At present, few studies have detailed microplastic characteristics and abundance along a freshwater–marine interface, and considerable uncertainties remain over the modelled contribution of terrestrial and riverine microplastic to the world’s oceans. In this article, for the first time, we detail sedimentary microplastic concentrations along a River–Sea transect from the lower reaches of a major continental river, the River Danube, through the Danube Delta, the Black Sea coast to the Romanian and Bulgarian inner shelf of the Black Sea. Our results indicate that isolated areas of the Danube Delta are still relatively pristine, with few microplastic particles in some of the sediments sampled.

scholarly journals Danube Delta: Water Management on the Sulina Channel in the Frame of Environmental Sustainability

2021 ◽  
Author(s):  
Igor Cretescu ◽  
Zsofia Kovacs ◽  
Liliana Lazar ◽  
Adrian Burada ◽  
Madalina Sbarcea ◽  
...  
Keyword(s):  
Black Sea ◽  
Environmental Sustainability ◽  
Treatment Plant ◽  
Seasonal Fluctuation ◽  
Biosphere Reserve ◽  
Danube River ◽  
The Black Sea ◽  
Danube Delta ◽  
Limit Value ◽  
Two Factors

The Danube Delta is the newest land formed by both transporting sediments brought by Danube River, which flows into the Black Sea and by traversing an inland region where water spreads and deposits sediments. Diurnal tidal action is low (only 8–9 cm), therefore the sediments would wash out into the water body faster than the river deposits it. However, a seasonal fluctuation of water level of 20 cm was observed in the Black Sea, contributing to alluvial landscape evolution in the Danube Delta. The Danube Delta is a very low flat plain, lying 0.52 m above Mean Black Sea Level with a general gradient of 0.006 m/km and only 20% of the delta area is below zero level. The main control on deposition, which is a combination of river, wind-generated waves, and tidal processes, depends on the strength of each one. The other two factors that play a major role are landscape position and the grain size distribution of the source sediment entering the delta from the river. The Danube Delta is a natural protected area in the South-Eastern part of Romania, declared a Biosphere Reserve through the UNESCO “Man and Biosphere” Programme. Water is a determining factor for all the human settlements in the Biosphere Reserve, the whole Danube Delta being structured by the three branches of the Danube (Chilia, Sulina and Sfantu Gheorghe (Saint George)). Our case study is focused on the Sulina branch, also named Sulina Channel, which offers the shortest distance between the Black Sea (trough Sulina Port) and Tulcea (the most important city of the Danube Delta from economic, social and cultural points of view) for both fluvial and marine ships. The improvement of water resources management is the main topic of this chapter, in terms of water quality indicators, which will be presented in twenty-nine monitoring points, starting since a few years ago and updated to nowadays. During the study period, significant exceedances of the limit value were detected in case of nitrate-N (3.9–4.6 mg/L) at the confluence (CEATAL 2) with the Saint George branch and in the Sulina Channel after the Wastewaters Treatment Plant (WWTP) discharge area, as well as near two settlements, namely Gorgova and Maliuc. The higher concentrations of Nitrogen-based nutrients were caused by the leakage from the old sewage systems (where these exist) and the diffuse loads.

The Pliocene deposits of the Black Sea Shelf east of the Danube River Delta

2020 ◽  
pp. SP505-2019-102
Author(s):  
Petro F. Gozhik ◽  
Valery E. Rokitsky
Keyword(s):  
Black Sea ◽  
River Delta ◽  
Danube River ◽  
Core Material ◽  
The Black Sea ◽  
Danube Delta ◽  
The Danube River ◽  
Continental Deposits ◽  
Circular Current ◽  
The One

AbstractThis paper provides analysis of the published materials on the occurrences of the Dacian and Cimmerian molluscs in the Danube River valley as well as the results of Pliocene sediments study based on core material of the boreholes drilled at the Black Sea Shelf east of the Danube River Delta.In the early Pontian time, the Dacian Basin was a large sub-basin of Paratethys which, due to an abrupt drop in sea level, separated into the Euxinian, Dacian and Caspian basins. At the end of the Bosphorus time, the discharge of the Dacian Basin waters into the Euxinian Basin formed a wide valley from the Galati-Reni region to the east through the Galati gateway. During the Cimmerian transgression, a vast bay existed on the site of the modern Danube Delta, from which mutual migrations of the Dacian and Cimmerian molluscs took place along the runoff valley. The cessation of runoff occurred during the regressive phase of the Late Cimmerian. The rhythmically bedded thick strata originated during the existence of the runoff valley. These strata were identified as the Pridanubian Formation (Suite). The cryptogenic form of Tulotoma Tulotoma (=Viviparus) ovidii nasonis (Bogachev) is characteristic of the lower and middle parts of the suite. The presence of the Dacian and Cimmerian molluscs in this suite became the basis for the correlation of sediments of the Dacian and Cimmerian regional stages. The Duabian molluscs were registered in the Cimmerian deposits of the Transcaucasus (the Duabian layers), Priazovye and the Kerch–Taman region. The migration of these molluscs took place during the regressive phases due to the circular current in the Euxinian Basin similar to the one existing in the Black Sea today.The Pliocene formation contains marine and continental deposits of the Lower and Upper Pliocene, which are represented by the Pridanubian Formation (Lower and Upper), Cimmerian deposits (non-subdivided Lower and Middle Cimmerian), Lower Kujalnician deposits, Upper Poration deposits, complex of red-coloured palaeosols (the Upper Miocene–Lower Pliocene non-subdivided).The formation of the Pliocene sediments on the Black Sea Shelf, east of the Danube Delta, was controlled by the inter-basin connectivity of the Eastern Paratethys.

scholarly journals Anthropogenic impact on the shores and the bottom of the Jebriyan bay in the Northwestern part of the Black Sea

2021 ◽  
Vol 30 (4) ◽  
pp. 729-740
Author(s):  
Yuriy D. Shuisky ◽  
Galina V. Vykhovanetz ◽  
Ludmila V. Organ ◽  
Mukete Theophilus N. Moto
Keyword(s):  
Black Sea ◽  
Anthropogenic Impact ◽  
Danube River ◽  
Nature Management ◽  
The Black Sea ◽  
Northwestern Part ◽  
Northern Coast ◽  
Danube Delta ◽  
Average Depth ◽  
The Impact

The Jebriyan Bay is located in the northern part of the Kiliya Danube Delta, at a junction of the delta cone and the indigenous coast. This is a zone of very high anthropogenic impact on the Danube Biosphere Reserve. The two opposite shores of this bay are fundamentally different. Along the northern shore, the Northwest coastal sand sediment flows discharge from the Cape of the Great Fontanne to the Jebriyan Bay. That is why the northern coast of the bay is made up of sandy forms of coastal topography (marine accumulative terrace and spit). The southern coast is deltaic; composed of a mixture of muddy, siltstone and sandy sediments. The area of the bay is limited to isobaths –11 m and is about 80 km2. The bottom of the bay has a gentle relief, made up of smooth outlines, with an average depth of 6.2 m. The shape of the transverse profile of the underwater slope is mostly convex. The natural system of the bay was affected by fishing, recreation, shipping and industrial sand production on coastal accumulative landforms. Coastal fishing uses a system of fixed bottom seines and small motorized floating equipment. Recreational facilities are designed to serve about 350 thousand people during the warm period each year. The impact of shipping was expressed in the construction and operation of the seaport of Ust-Dunaysk, together with suitable canal and the technical canal between the sea and the branch of the delta breakthrough the system of the large Ochakov branch. The ladle port had an area of about 1.5 km2, a maximal depth of 16 m, and an average depth of 13.7 m. The trough was connected to the Ochakov branch of the Danube Delta by a technical canal with a depth of 4 m. Vessels could enter the harbor of Ust-Danube through an access navigation channel with a depth of 11–12 m and a bottom width of 125 m. The port was used for the transshipment of large containers, general forest cargo from ocean vessels (displacement of 60–100 thousand tons) on regular sea lines from the countries of Southeast Asia to the Black Sea, to the Danube and further to the countries of Central Europe and to the ports of the North and the Baltic Seas. But it was unfortunate that the port construction site did not last as expected. Between 1980–2010 the harbor and approach canal of Ust-Dunaysk were filled with Danube river sediments. The example of Jebriyan Bay has shown that when executing any type of sustainable nature management project, it is very important to take into account the natural milieu.

scholarly journals MONITOX international network for monitoring of environmental toxicants and risk assessment in the Black Sea basin: research and interdisciplinary cooperation dimensions

2021 ◽  
Author(s):  
Antoaneta Ene ◽  
◽  
Elena Zubcov ◽  
Thomas Spanos ◽  
Oleg Bogdevich ◽  
...  
Keyword(s):  
Black Sea ◽  
Temporal Distribution ◽  
Interdisciplinary Studies ◽  
Danube River ◽  
The Black Sea ◽  
Toxic Substances ◽  
Environmental Toxicants ◽  
Danube Delta ◽  
Republic Of Moldova ◽  
Sea Coast

The paper presents the main tackled issues and results concerning the monitoring of the toxic substances (TOXs) in the network established in the frame of BSB27 MONITOX project, implemented by «Dunarea de Jos» University of Galati, Romania (Leader Partner) in partnership with Institute of Zoology, Republic of Moldova, International Hellenic University (IHU), Greece, Institute of Geology and Seismology, Republic of Moldova (IGS), and “Danube Delta” National Institute for Research and Development, Tulcea, Romania. Maps of pollution of water, sediments, soils and biota with TOXs built using ArcGIS and Q-GIS highlight their levels and spatial-temporal distribution in the target zones in the three countries: Danube River (Lower sector), Prut and Dniester Rivers, Danube Delta, Black Sea coast, Nestos River and delta and Northern Aegean Sea coast. The strategy designed and results of the interdisciplinary studies performed in the period 2018-2021 on a large range of toxic pollutants in the Black Sea Basin (including NE part of Greece) are emphasized, as well as the assessment of toxicants’ impact upon human health using a health risk calculator developed as ICT tool.

scholarly journals The Black Sea Trout, Salmo labrax Pallas, 1814 (Pisces: Salmonidae) in Romanian Waters

2020 ◽  
Vol 77 (2) ◽  
pp. 9
Author(s):  
Călin LAȚIU ◽  
Daniel COCAN ◽  
Paul UIUIU ◽  
Andrada IHUȚ ◽  
Sabin Alexandru NICULA ◽  
...  
Keyword(s):  
Black Sea ◽  
The Black Sea ◽  
Danube Delta ◽  
Meristic Characters ◽  
Sea Trout ◽  
Research Fields ◽  
New Information ◽  
Rivers And Lakes ◽  
Recorded Data ◽  
New Hypothesis

The review assembles chronological data on Black Sea trout (Salmo labrax) from Romanian waters and brings up-to-date information related to the distribution of the species. The information used dates from 1909 to 2020 and includes books, articles, digital databases, field observations, and notes from different research fields such as ichthyology, biogeography, genetics, aquaculture, conservation, and ecology. Global distribution, migration, meristic characters, and aquaculture of the species were analyzed based on the recorded data from the specialty literature. New information related to a possible population of Salmo labrax inside the Carpathian Arch was discussed. In Romanian waters the species is found in the Black Sea, Danube, Danube Delta but the current paper proposes a new hypothesis, namely that resident populations can be found in rivers and lakes adjacent to the Carpathian Arch. The highest migration point of the Black Sea trout in the Danube was recorded near Corabia locality, Olt County, (43°46′25″N- 24°30′12″E). In the Danube Delta, it was caught in all the three branches (Sulina, Sf. Gheorghe and Chilia), and lagoonary complexes such as Razim-Sinoe. Sexually matured females were caught especially in Spring Season while unmatured specimens were caught in all seasons. Even if the species is protected under Romanian legislation, fishermen and anglers should report its presence when caught accidentally.

scholarly journals Consorts of gastropod Rapana venosa (Valenciennes, 1846) in the Northern Black Sea. Part I: Porifera, Cnidaria, Bryozoa, Chordata

2017 ◽  
Vol 2 (2) ◽  
pp. 20-33 ◽  
Author(s):  
I. P. Bondarev ◽  
N. K. Revkov
Keyword(s):  
Surface Area ◽  
Coastal Zone ◽  
Black Sea ◽  
The Black Sea ◽  
Bottom Fauna ◽  
Depth Range ◽  
Shell Surface ◽  
Rapana Venosa ◽  
The Core ◽  
Rapa Whelk

Gastropod mollusk-invader Rapana venosa (Valenciennes, 1846) in the 1940s took a free ecological niche terminal predator in benthic communities of the Black Sea shelf and has become an important element of the ecosystem. The ability of rapa whelk to have a devastating impact on the biocenosis filter feeders determines the necessity of constant monitoring of this species populations’ state. The study of rapa whelk showed that the ecological role of this species is not limited to predation. Fairly large shell R. venosa is a solid substrate for alga, attached and restrictedly movable (sedentary) benthic animal organisms, among which mobile free-living forms sometimes find shelter. The aim of the work is to describe specific complex of epibiotic organisms formed on rapa-whelk shells, which is regarded as a consortium, where of R. venosa is the core. To study the consort community of R. venosa a sampling was made in 7 regions of the northern part of the Black Sea: 1 – Mamaia beach, Romania, 2 – the north-western part of the Black Sea (NWBS), Crimean sector, 3 – Sevastopol, 4 – Alupka, 5 – Yalta – Alushta, 6 – Karadag, 7 – the Kerch Strait. The sampling in the coastal zone (less then 15 m depth) was carried out by SCUBA and snorkel diving, deeper (up to 40 m) was used “Ocean-50”grab corer was used. Totally of 856 specimens of R. venosa were collected and analyzed. The main bulk of the material in the amount of 750 specimens of R. venosa was sampled in the coastal zone in Sevastopol vicinity (south-western Crimea) at the depth range of 1.5–10.0 m. The collection of the rapa whelk specimens was carried out totally and each specimen was placed in a separate plastic bag indicating the collection area, depth and biotope. Along with the mollusks sampling, visual observations and photographic fixation of hydrobionts in situ were carried out. Based on the research results the taxonomic list of rapa whelk epibiotic organisms was extended and for the first time the taxonomic composition of the mobile forms permanently or temporarily present in the R. venosa consortium was given. The first part of the investigation provides a list of rapa whelk epibionts taxa relating to four (Porifera, Cnidaria, Bryozoa, Chordata) of the seven detected Phyla with indication of sampling depths and bottom type and comments on the frequency of occurrence, the quantity and of their interaction with the consortium core. Phylum Porifera is represented by 1, Bryozoa – 3 Cnidaria – 2 and Chordata – 4 species. The drilling sponge Pione vastifica was found in all the investigated areas, except region 2 (NWBS), with a frequency of 20 to 90 % and the shell surface area damage was up to 100 % (average 30–35 %). Not numerous representatives of Cnidaria were found singly in the region 3 (Actinia equina) and in the region 5 (Diadumene lineata). Bryozoans are the most common group of animal-consorts of rapa whelk present in all the areas of our research. The frequency of their occurrence ranged from 10 to 100 %, the covering area of the shell surface was from 0 to 85 %. More than 90 % of the total surface area of rapana shell cover with bryozoans and their occurrence is in Cryptosula pallasiana. The second bryozoans’ species on development indices is Conopeum seurati, which was found in areas 3, 6 and 7, where the occurrence was up to 30 % and the coverage was up to 25 %. The other 3 species of bryozoans (Schizomavella auriculata, Bowerbankia imbricata, Hippothoa sp.) were found rarely. Representatives of Chordata – 2 species of ascidians (Botryllus schlosseri, Ciona intestinalis) and 3 species of fish (Diplecogaster bimaculata, Parablennius tentacularis, Scorpaena porcus) were recorded singly in regions 2, 3, 5. For the four Phyla of animal organisms considered the consorts list of R. venosa of the sandy bottom biotopes (10 species) is twice more numerous than that of the rocky eco-form (5 species). The organisms studied are of a different degree and nature of relations with the core consortium from commensalism to parasitism. Generalized information on periphyton and total coverage of rapa whelk shells with epibiotic complex is given. The results of the work show that in the Black Sea R. venosa has become an important element of the ecosystem, increasing biological diversity of the bottom fauna due to the formation of its own consortium complexes of epibiontic organisms.

scholarly journals Modern state of the reproductive potential of Black Sea sprat Sprattus sprattus phalericus (Risso, 1826) (Pisces: Clupeidae) in Crimean region and conditions for its formation

2019 ◽  
Vol 4 (4) ◽  
pp. 3-14
Author(s):  
G. V. Zuyev
Keyword(s):  
Black Sea ◽  
Average Length ◽  
Reproductive Potential ◽  
Danube River ◽  
The Black Sea ◽  
Total Catch ◽  
Sprattus Sprattus ◽  
The Absolute ◽  
Individual Fecundity

Black Sea sprat Sprattus sprattus phalericus (Risso, 1826) is one of the abundant species of fish in the Sea of Azov – Black Sea basin. Due to its large number sprat plays an extremely important role in the ecosystem of the sea, being an intermediate link between zooplankton and representatives of the highest trophic level – large predatory fish, dolphins, and birds. At the same time sprat is one of the important commercial fish in all the Black Sea countries, steadily being on the second place of catch volume in recent decades (after anchovy). The total catch reaches 100 thousand tons. Turkey and Ukraine are the main producing countries. Monitoring and forecast of biological state of sprat population with rising fishing intensity and climate changes are urgent tasks. The research subject of this article is the long-term (2000–2016) dynamics of biological (qualitative) parameters determining the population fecundity of Black Sea sprat in Crimean region, the current state of reproductive potential, and the conditions for its formation. The article is based on the results of own research. Parameters determining the population fecundity – the length-age structure of the spawning part population, the absolute individual fecundity, and the sex structure population (ratio between females and males) – were studied. In the long-term plan (in 2011–2016 compared with 2000–2004) the average length of spawning females decreased by 1.22 times (from 7.36 to 6.03 cm). It was accompanied by a decrease in the absolute individual fecundity by 2.39 times (from 13 625 to 5690 eggs). The numerical ratio between females and males decreased by 1.23 times (from 1.95 to 1.59). Simultaneously the sprat stock in the northern part of the Black Sea was reduced by more than 2.5 times (from > 500 thousand tons to < 200 thousand tons). As a result, the population fecundity of sprat in Crimean region decreased by more than 7 times (2.39 × 1.23 × 2.5). The conditions of sprat fishing in the northern part of the Black Sea (from the mouth of the Danube River to the Kerch Strait) were studied. They showed 2-fold decrease (from 251.9 thousand tons in 2000–2004 to 129.1 thousand tons in 2011–2016) in the total catch and more than 2.3-fold decrease (from 50.4 to 21.4 thousand tons) in average annual catch in this region. On the contrary, in the Crimean shelf the total catch at that time increased by 1.2 times (from 76.9 to 92.2 thousand tons), and its average annual value remained constant (15.4 thousand tons). While reducing the stock by 2.5 times, this means that the fishing pressure on the Crimean population increased 2.5 times. This fact suggests considering the factor of fishing as the main cause of its degradation. Validity of this version is confirmed by the fact of conjugacy (inverse connection) of interannual fluctuations between the catch and the length-age parameters of sprat in Crimean region in 2003–2013 previously found: catches over 15–16 thousand tons were accompanied by a next year decrease in the fish average length. Regulation of fishing is a necessary condition for preventing further degradation, for restoring and maintaining sustainable state of sprat population in Crimean region and its reproductive potential. The negative impact of natural (climatic and trophic) factors on the state of the population should be recognized as a secondary one. Local overfishing indicates indirectly the structuring of the commercial stock of Black Sea sprat, its division into a number of geographical aggregations (stock units), i. e. the presence of intraspecific differentiation.

Late Miocene sediment delivery from the axial drainage system of the East Carpathian foreland basin to the Black Sea

Geology ◽  
2020 ◽  
Vol 48 (8) ◽  
pp. 761-765 ◽  
Author(s):  
Arjan de Leeuw ◽  
Stephen J. Vincent ◽  
Anton Matoshko ◽  
Andrei Matoshko ◽  
Marius Stoica ◽  
...  
Keyword(s):  
Black Sea ◽  
Late Miocene ◽  
Drainage System ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Danube River ◽  
The Black Sea ◽  
Foreland Basins ◽  
Continental Scale ◽  
Slab Breakoff

Abstract We describe a late Miocene to early Pliocene axial drainage system in the East Carpathian foreland, which was an important sediment supplier to the Black Sea and the Dacian Basin. Its existence explains the striking progradation of the northwest Black Sea shelf prior to the onset of sediment supply from the continental-scale Danube River in the late Pliocene to Pleistocene. This axial drainage system evolved due to the diachronous along-strike evolution of the Carpathians and their foreland; continental collision, overfilling, slab breakoff, and subsequent exhumation of the foreland occurred earlier in the West Carpathians than in the East Carpathians. After overfilling of the western foreland, excess sediment was transferred along the basin axis, giving rise to a 300-km-wide by 800-km-long, southeast-prograding river-shelf-slope system with a sediment flux of ∼12 × 103 km3/m.y. Such late-stage axial sediment systems often develop in foreland basins, in particular, where orogenesis is diachronous along strike. Substantial lateral sediment transport thus needs to be taken into account, even though evidence of these axial systems is often eroded following slab breakoff and inversion of their foreland basins.

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