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Black Sea

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Title: Black Sea  
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Black Sea

Black Sea
Type Sea
Primary inflows Danube, Dnieper, Rioni, Southern Bug, Kızılırmak, Dniester
Primary outflows Bosphorus
Basin countries Turkey
Max. length 1,175 km (730 mi)
Surface area 436,402 km2 (168,500 sq mi)
Average depth 1,253 m (4,111 ft)
Max. depth 2,212 m (7,257 ft)
Water volume 547,000 km3 (131,200 cu mi)
Islands 10+
The Black Sea in Georgia
Photo of the Black Sea near Gagra, Abkhazia, Russian Empire taken in 1915

The Black Sea is a sea in Southeastern Europe. It is bounded by Europe, Anatolia and the Caucasus, and drains through the Mediterranean into the Atlantic Ocean, via the Aegean Seas and various straits. The Bosphorus Strait connects it to the Sea of Marmara, and the Strait of the Dardanelles connects that sea to the Aegean Sea region of the Mediterranean. These waters separate eastern Europe and western Asia. The Black Sea is also connected to the Sea of Azov by the Strait of Kerch.

The Black Sea has an area of 436,400 km2 (168,500 sq mi) (not including the Sea of Azov),[1] a maximum depth of 2,212 m (7,257 ft),[2] and a volume of 547,000 km3 (131,000 cu mi).[3] The Black Sea forms in an east-west trending elliptical depression which lies between Romania, Russia, Turkey, and Ukraine.[4] It is constrained by the Pontic Mountains to the south and by the Caucasus Mountains to the east, and features a wide shelf to the northwest. The longest east-west extent is about 1,175 km (730 mi).

Important cities along the coast include Batumi, Burgas, Constanța, Giresun, Hopa, Istanbul, Kerch, Mangalia, Năvodari, Novorossiysk, Odessa, Ordu, Poti, Rize, Samsun, Sevastopol, Sochi, Sukhumi, Trabzon, Varna, Yalta and Zonguldak.

The Black Sea has a positive water balance; that is, a net outflow of water 300 km3 (72 cu mi) per year through the Bosphorus and the Dardanelles into the Aegean Sea. Mediterranean water flows into the Black Sea as part of a two-way hydrological exchange. The Black Sea outflow is cooler and less saline, and floats over the warm, more saline Mediterranean inflow – as a result of differences in density caused by differences in salinity – leading to a significant anoxic layer well below the surface waters. The Black Sea also receives river water from large Eurasian fluvial systems to the north of the Sea, of which the Don, Dnieper and Danube are the most significant.

In the past, the water level has varied significantly. Due to these variations in the water level in the basin, the surrounding shelf and associated aprons have sometimes been land. At certain critical water levels it is possible for connections with surrounding water bodies to become established. It is through the most active of these connective routes, the Turkish Straits, that the Black Sea joins the world ocean. When this hydrological link is not present, the Black Sea is an endorheic basin, operating independently of the global ocean system. Currently the Black Sea water level is relatively high, thus water is being exchanged with the Mediterranean. The Turkish Straits connect the Black Sea with the Aegean Sea, and comprise the Bosphorus, the Sea of Marmara and the Dardanelles.


  • Extent 1
  • Population 2
  • Name 3
    • Modern names 3.1
    • Historical names 3.2
  • Geology and bathymetry 4
  • Hydrology 5
  • Hydrochemistry 6
  • Ecology 7
    • Phytoplankton 7.1
    • Endemic animal species 7.2
    • Ecological effects of pollution 7.3
  • Climate 8
  • History 9
    • Mediterranean connection during the Holocene 9.1
      • Deluge hypothesis 9.1.1
    • Recorded history 9.2
    • Archaeology 9.3
  • Modern use 10
    • Commercial and civic use 10.1
      • Navigation 10.1.1
        • Ports and ferry terminals
        • Merchant fleet and traffic
      • Fishing 10.1.2
      • Hydrocarbons exploration 10.1.3
      • Holiday resorts and spas 10.1.4
    • Modern military use 10.2
      • International and military use of the Straits 10.2.1
      • 2008 South Ossetia War 10.2.2
      • 2014 Crimean crisis 10.2.3
  • Trans-sea cooperation 11
  • See also 12
  • Notes 13
  • References 14
  • Bibliography 15
  • External links 16



  • Space Monitoring of the Black Sea Coastline and Waters
  • Pictures of the Black sea coast all along the Crimean peninsula
  • China: China wants to build a "Black Sea" highway Agriculture in the Black Sea Region (BS-AGRO.COM)
  • Black Sea Environmental Internet Node
  • Black Sea Organization for Integration and Sustainable Development
  • Black Sea-Mediterranean Corridor during the last 30 ky: UNESCO IGCP 521 WG12

External links

  • Stella Ghervas, "Odessa et les confins de l'Europe: un éclairage historique", in Stella Ghervas et François Rosset (ed), Lieux d'Europe. Mythes et limites, Paris, Editions de la Maison des sciences de l'homme, 2008. ISBN 978-2-7351-1182-4
  • Charles King, The Black Sea: A History, 2004, ISBN 0-19-924161-9
  • William Ryan and Walter Pitman, Noah's Flood, 1999, ISBN 0-684-85920-3
  • Neal Ascherson, Black Sea (Vintage 1996), ISBN 0-09-959371-8
  • Özhan Öztürk. Karadeniz: Ansiklopedik Sözlük (Black Sea: Encyclopedic Dictionary). 2 Cilt (2 Volumes). Heyamola Publishing. Istanbul.2005 ISBN 975-6121-00-9.
  • Rüdiger Schmitt, "Considerations on the Name of the Black Sea", in: Hellas und der griechische Osten (Saarbrücken 1996), pp. 219–224
  • West, Stephanie (2003). ‘The Most Marvellous of All Seas’: the Greek Encounter with the Euxine 50 (2). Greece & Rome. pp. 151–167. 
  • Petko Dimitrov, Dimitar Dimitrov (2004. ISBN 954-579-335-X, 91p.). THE BLACK SEA, THE FLOOD AND THE ANCIENT MYTHS. Varna. 
  • Dimitrov, D (2010). Geology and Non-traditional resources of the Black Sea. LAP Lambert Academic Publishing. p. 244.  


  1. ^ Surface Area—"Black Sea Geography". University of Delaware College of Marine Studies. 2003. Retrieved April 3, 2014. 
  2. ^ Maximum Depth—"Europa – Gateway of the European Union Website". Environment and Enlargement – The Black Sea: Facts and Figures. 
  3. ^ "Unexpected changes in the oxic/anoxic interface in the Black Sea". Nature Publishing Group. March 30, 1989. Retrieved December 2, 2006. 
  4. ^  
  5. ^ "Limits of Oceans and Seas, 3rd edition". International Hydrographic Organization. 1953. Retrieved February 7, 2010. 
  6. ^ "Turkish Statistical Institute". Retrieved 2014-01-14. 
  7. ^ "Turkish Statistical Institute". Retrieved 2014-01-14. 
  8. ^ This place is located on the Crimean Peninsula, most of which is the subject of a territorial dispute between Russia and Ukraine. According to the political division of Russia, located on the peninsula are the federal subjects of the Russian Federation (the Republic of Crimea and the federal city of Sevastopol). According to the administrative-territorial division of Ukraine, located on the peninsula are the Ukrainian divisions (the Autonomous Republic of Crimea and the city with special status of Sevastopol).
  9. ^ "Turkish Statistical Institute". Retrieved 2014-01-14. 
  10. ^ "Cele mai mari orase din Romania". Retrieved 2014-01-14. 
  11. ^ "Turkish Statistical Institute". Retrieved 2014-01-14. 
  12. ^ Özhan Öztürk (2005). Karadeniz Ansiklopedik Sözlük. İstanbul: Heyamola Yayınları. pp. 617–620. 
  13. ^ Gibbon, Edward. The History of the Decline and Fall of the Roman Empire. Everyman's Library, 1910; reprinted 1993. ISBN 0-679-42308-7. Passim.
  14. ^ McKenzie, DP (1970). "Plate tectonics of the Mediterranean region". Nature 226 (5242): 239–43.  
  15. ^ McClusky, S., S. Balassanian, et al. (2000). "Global Positioning System constraints on plate kinematics and dynamics in the eastern Mediterranean and Caucasus".  
  16. ^ a b Shillington, Donna J.; White, Nicky; Minshull, Timothy A.; Edwards, Glyn R.H.; Jones, Stephen M.; Edwards, Rosemary A.; Scott, Caroline L. (2008). "Cenozoic evolution of the eastern Black Sea: A test of depth-dependent stretching models". Earth and Planetary Science Letters 265 (3–4): 360–378.  
  17. ^ Nikishin, A (2003). "The Black Sea basin: tectonic history and Neogene–Quaternary rapid subsidence modelling". Sedimentary Geology 156: 149–168.  
  18. ^ Remote Sensing of the European Seas. 2008. p. 17.  
  19. ^ Prothero, G.W. (1920). Anatolia. London: H.M. Stationery Office. 
  20. ^ "Agriculture in the Black Sea Region". Retrieved 2014-01-14. 
  21. ^ a b c d e f g Descriptive Physical Oceanography. Talley, Pickard, Emery, Swift.
  22. ^ "Meromictic". Retrieved 2014-01-14. 
  23. ^ "Exploring Ancient Mysteries: A Black Sea Journey". Retrieved 2014-01-14. 
  24. ^ a b Korotaev, G. (2003). "Seasonal, interannual, and mesoscale variability of the Black Sea upper layer circulation derived from altimeter data". Journal of Geophysical Research 108.  
  25. ^ Black Sea Becomes Turquoise Retrieved 2 December 2006.
  26. ^ Schuiling, Roelof Dirk; Cathcart, Richard B.; Badescu, Viorel; Isvoranu, Dragos; Pelinovsky, Efim (2006). "Asteroid impact in the Black Sea. Death by drowning or asphyxiation?". Natural Hazards 40 (2): 327–338.  
  27. ^
  28. ^ a b c d Oguz, T., H. W. Ducklow, et al. (1999). "A physical-biochemical model of plankton productivity and nitrogen cycling in the Black Sea". Deep Sea Research Part I: 46 (4): 597–636.  
  29. ^ a b c Oguz, T. and A. Merico (2006). "Factors controlling the summer Emiliania huxleyi bloom in the Black Sea: A modeling study". Journal of Marine Systems 59 (3–4): 173–188.  
  30. ^ Friedrich, J., C. Dinkel, et al. (2002). "Benthic Nutrient Cycling and Diagenetic Pathways in the North-western Black Sea". Estuarine, Coastal and Shelf Science 54 (3): 369–383.  
  31. ^ Eker, E., L. Georgieva, et al. (1999). "Phytoplankton distribution in the western and eastern Black Sea in spring and autumn 1995". ICES Journal of Marine Science 56: 15–22.  
  32. ^ a b Eker-Develi, E (2003). "Distribution of phytoplankton in the southern Black Sea in summer 1996, spring and autumn 1998". Journal of Marine Systems 39 (3–4): 203–211.  
  33. ^ Krakhmalny, A. F. (1994). "Dinophyta of the Black Sea (Brief history of investigations and species diversity)." Algologiya 4: 99–107.
  34. ^ a b Gomez, F. and L. Boicenco (2004). "An annotated checklist of dinoflagellates in the Black Sea".  
  35. ^ Uysal, Z (2006). "Vertical distribution of marine cyanobacteria Synechococcus spp. in the Black, Marmara, Aegean, and eastern Mediterranean seas". Deep Sea Research Part II: Topical Studies in Oceanography 53 (17–19): 1976–1987.  
  36. ^ Humborg, Christoph; Ittekkot, Venugopalan; Cociasu, Adriana; Bodungen, Bodo v. (1997). "Effect of Danube River dam on Black Sea biogeochemistry and ecosystem structure". Nature 386 (6623): 385–388.  
  37. ^ Sburlea, A., L. Boicenco, et al. (2006). "Aspects of eutrophication as a chemical pollution with implications on marine biota at the Romanian Black Sea shore". Chemicals as Intentional and Accidental Global Environmental Threats. NATO Security through Science Series: 357–360.  
  38. ^ Gregoire, M., C. Raick, et al. (2008). "Numerical modeling of the central Black Sea ecosystem functioning during the eutrophication phase". Progress in Oceanography 76 (3): 286–333.  
  39. ^ Colin Woodard (11 February 2001). Ocean's end: travels through endangered seas. Basic Books. pp. 1–28.  
  40. ^ Lancelot, C (2002). "Modelling the Danube-influenced North-western Continental Shelf of the Black Sea. II: Ecosystem Response to Changes in Nutrient Delivery by the Danube River after its Damming in 1972". Estuarine, Coastal and Shelf Science 54 (3): 473–499.  
  41. ^ Woodard, Colin, "The Black Sea's Cautionary Tale," Congressional Quarterly Global Researcher, October 2007, pp. 244–245
  42. ^ Hurrell, J. W. (1995). "Decadal Trends in the North Atlantic Oscillation: Regional Temperatures and Precipitation". Science 269 (5224): 676–679.  
  43. ^ Lamy, F., Arz, H. W., Bond, G. C., Barh, A. and Pätzold, J. (2006). "Multicentennial-scale hydrological changes in the Black Sea and northern Red Sea during the Holocene and the Arctic/North Atlantic Oscillation". Paleoceanography 21.  
  44. ^ "Spatial and temporal analysis of annual rainfall variations in Turkey".  
  45. ^ Cullen, H. M., A. Kaplan, et al. (2002). "Impact of the North Atlantic Oscillation on Middle Eastern climate and streamflow". Climatic Change 55 (3): 315–338.  
  46. ^ Ozsoy, E. and U. Unluata (1997). "Oceanography of the Black Sea: A review of some recent results". Earth-Science Reviews 42 (4): 231–272.  
  47. ^ Brody, L. R., Nestor, M.J.R. (1980). Regional Forecasting Aids for the Mediterranean Basin. Handbook for Forecasters in the Mediterranean, Naval Research Laboratory. Part 2.
  48. ^ William Ryan and Walter Pitman (1998). Noah's Flood: The New Scientific Discoveries About the Event That Changed History. New York:  
  49. ^ David Nicolle (1989). The Venetian Empire 1200-1670.  
  50. ^ Bruce McGowan. Economic Life in Ottoman Europe: Taxation, Trade and the Struggle for Land, 1600-1800, Studies in Modern Capitalism. p. 134.  
  51. ^ "Black Sea Security". NATO Advanced Research Workshop. NATO. 2010. Retrieved 2010. 
  52. ^ a b "Черное море признано одним из самых неблагоприятных мест для моряков".  
  53. ^
  54. ^ "Bulgarian Sea Resorts". Retrieved 2007-02-02. 
  55. ^ "Montreaux and The Bosphorus Problem" (in Türkçe). 
  56. ^ "Montreaux Convention and Turkey (pdf)" (PDF). 


  1. ^ a b Abkhazia has been a de facto independent republic since 1992, although remains a de jure autonomous republic of Georgia.


See also

Trans-sea cooperation

2014 Crimean crisis

2008 South Ossetia War

The 1936 Montreux Convention governs the passage of vessels between the Black and the Mediterranean Seas and the presence of military vessels belonging to non-littoral states in the Black Sea waters.[56]

Ukrainian Navy artillery boat U170 in the Bay of Sevastopol

The 1936 Montreux Convention provides for a free passage of civilian ships between the international waters of the Black and the Mediterranean Seas. However, a single country (Turkey) has a complete control over the straits connecting the two seas. The 1982 amendments to the Montreux Convention allow Turkey to close the Straits at its discretion in both wartime and peacetime.[55]

International and military use of the Straits

Modern military use

In the years following the end of the Cold War, the popularity of the Black Sea as a tourist destination steadily increased. Tourism at Black Sea resorts became one of the region's growth industries.[54] The following is a list of well-known Black Sea resorts:

Yalta, Crimea
Ordzhonikidze health resort in Sochi, Russia
Amasra, Turkey, is located on a small island in the Black Sea
Black Sea coast with subtropical flora in Gagra, Abkhazia
Cities of the Black Sea

Holiday resorts and spas

Since the 1980s, the Soviet Union started offshore drilling for petroleum in the sea's western portion (adjoining Ukraine's coast). The independent Ukraine continued and intensified that effort within its Exclusive Economic Zone, inviting major international oil companies for exploration. Discovery of the new, massive oilfields in the area stimulated an influx of foreign investments. It also provoked a short-term peaceful territorial dispute with Romania which was resolved in 2011 by an international court redefining the Exclusive Economic Zones between the two countries.

Hydrocarbons exploration

Anchovy: the Turkish commercial fishing fleet catches around 300.000 tons per year on average, and fishery carried out mainly in winter and the highest portion of the stock is exploited between November and December.[53]


According to the International Transport Workers' Federation 2013 study, there were around 2,400 commercial vessels operating in the Black Sea.[52]

Merchant fleet and traffic

According to the International Transport Workers' Federation 2013 study, there were at least 30 operating merchant seaports in the Black Sea (including at least 12 in Ukraine).[52]

Ports and ferry terminals


According to NATO, the Black sea is a strategic corridor that provides smuggling channels for moving legal and illegal goods including drugs, radioactive materials, and counterfeit goods that can be used to finance terrorism.[51]

Commercial and civic use

Modern use

Perhaps the most promising areas in deepwater archaeology are the quest for submerged prehistoric settlements in the continental shelf and for ancient shipwrecks in the anoxic zone, which are expected to be exceptionally well preserved due to the absence of oxygen. This concentration of historical powers, combined with the preservative qualities of the deep anoxic waters of the Black Sea, has attracted increased interest from marine archaeologists who have begun to discover a large number of ancient ships and organic remains in a high state of preservation.

Ancient trade routes in the region are currently being extensively studied by scientists, as the Black Sea was sailed by Poles, Tatars, Ottomans, and Russians.


The Black Sea was a significant naval theatre of World War I and saw both naval and land battles during World War II.

The Black Sea became an Ottoman Navy lake within five years of Genoa losing the Crimea in 1479, after which the only Western merchant vessels to sail its waters were those of Venice's old rival Ragusa. This restriction was gradually changed by the Russian Navy from 1783 until the relaxation of export controls in 1789 because of the French Revolution.[49][50]

Ivan Aivazovsky. Black Sea Fleet in the Bay of Theodosia, just before the Crimean War.

The steppes to the north of the Black Sea have been suggested as the original homeland (Urheimat) of the speakers of the Proto-Indo-European language, (PIE) the progenitor of the Indo-European language family, by some scholars such as Marija Gimbutas; others move the heartland further east towards the Caspian Sea, yet others to Anatolia. Numerous ancient ports, some older than the Egyptian pyramids, line the Black Sea's coasts.

The oldest processed gold in the world, arguably left by Georgia), marked for the Greeks the edge of the known world.

The Black Sea was a busy waterway on the crossroads of the ancient world: the Balkans to the west, the Eurasian steppes to the north, Caucasus and Central Asia to the east, Asia Minor and Mesopotamia to the south, and Greece to the south-west.

A medieval map of the Black Sea by Diogo Homem.

Recorded history

In 1997, William Ryan and Walter Pitman from Columbia University published a hypothesis according to which a massive flood through the Bosphorus occurred in ancient times. They claim that the Black and Caspian Seas were vast freshwater lakes, but then about 5600 BC, the Mediterranean spilled over a rocky sill at the Bosphorus, creating the current communication between the Black and Mediterranean Seas. Subsequent work has been done both to support and to discredit this hypothesis, and archaeologists still debate it. Ryan and Pitman associate this catastrophe with ancient flood myths.[48]

Deluge hypothesis

In the aftermath of the last glacial period, water levels in the Black Sea and the Aegean Sea rose independently until they were high enough to exchange water. The exact timeline of this development is still subject to debate. One possibility is that the Black Sea filled first, with excess fresh water flowing over the Bosphorus sill and eventually into the Mediterranean Sea. There are also catastrophic scenarios, such as the "Black Sea deluge theory" put forward by William Ryan, Walter Pitman and Petko Dimitrov.

There is also evidence that water levels in the Black Sea were considerably lower at some point during the post-glacial period. Thus, for example, archaeologists found fresh-water snail shells and man-made structures in roughly 100 m (330 ft) of water off the Black Sea coast of modern Turkey. Therefore it is agreed that the Black Sea had been a landlocked freshwater lake (at least in upper layers) during the last glaciation and for some time after.

The Black Sea is connected to the World Ocean by a chain of two shallow straits, the Dardanelles and the Bosphorus. The Dardanelles is 55 m (180 ft) deep and the Bosphorus is as shallow as 36 m (118 ft). By comparison, at the height of the last ice age, sea levels were more than 100 m (330 ft) lower than they are now.

Map of the Dardanelles
The Bosphorus, taken from the International Space Station

Mediterranean connection during the Holocene


The relative strength of these systems also limits the amount of cold air arriving from northern regions during winter.[46] Other influencing factors include the regional topography, as depressions and storms systems arriving from the Mediterranean are funneled through the low land around the Bosphorus, Pontic and Caucasus mountain ranges acting as wave guides, limiting the speed and paths of cyclones passing through the region[47]

Short-term climatic variation in the Black Sea region is significantly influenced by the operation of the North Atlantic Oscillation, the climatic mechanisms resulting from the interaction between the north Atlantic and mid-latitude air masses.[42] While the exact mechanisms causing the North Atlantic Oscillation remain unclear,[43] it is thought the climate conditions established in western Europe mediate the heat and precipitation fluxes reaching Central Europe and Eurasia, regulating the formation of winter cyclones, which are largely responsible for regional precipitation inputs[44] and influence Mediterranean Sea Surface Temperatures (SST's).[45]

The ice on the Gulf of Odessa


Pollution reduction and regulation efforts have led to a partial recovery of the Black Sea ecosystem during the 1990s, and an EU monitoring exercise, 'EROS21', revealed decreased N and P values, relative to the 1989 peak.[40] Recently, scientists have noted signs of ecological recovery, in part due to the construction of new sewage treatment plants in Slovakia, Hungary, Romania, and Bulgaria in connection with membership in the European Union. Mnemiopsis leidyi populations have been checked with the arrival of another alien species which feeds on them.[41]

The decline in macrophytes was further compounded by overfishing during the 1970s, while the invasive ctenophore Mnemiopsis reduced the biomass of copepods and other zooplankton in the late 1980s. Additionally, an alien species—the warty comb jelly (Mnemiopsis leidyi)—was able to establish itself in the basin, exploding from a few individuals to an estimated biomass of one billion metric tons.[39] The change in species composition in Black Sea waters also has consequences for hydrochemistry, as Ca-producing coccolithophores influence salinity and pH, although these ramifications have yet to be fully quantified. In central Black Sea waters, Si levels were also significantly reduced, due to a decrease in the flux of Si associated with advection across isopycnal surfaces. This phenomenon demonstrates the potential for localised alterations in Black Sea nutrient input to have basin-wide effects.

Since the 1960s, rapid industrial expansion along the Black Sea coast line and the construction of a major dam has significantly increased annual variability in the N:P:Si ratio in the basin. In coastal areas, the biological effect of these changes has been an increase in the frequency of monospecific phytoplankton blooms, with diatom bloom frequency increasing by a factor of 2.5 and non-diatom bloom frequency increasing by a factor of 6. The non-diatoms, such as the prymnesiophytes Emiliania huxleyi (coccolithophore), Chromulina sp., and the Euglenophyte Eutreptia lanowii are able to out-compete diatom species because of the limited availability of Si, a necessary constituent of diatom frustules.[36] As a consequence of these blooms, benthic macrophyte populations were deprived of light, while anoxia caused mass mortality in marine animals.[37][38]

Ecological effects of pollution

Is another native fish that is also found in the Caspian Sea. It preys upon Zebra mussels. Like the mussels and common carp it has become invasive when introduced to other environments, like the Great Lakes.
The Common Carp's native range extends to The Black Sea along with the Caspian Sea and Aral Sea. Like the Zebra mussel the Common Carp is an invasive species when introduced to other habitats.
The Black Sea along with the Caspian Sea is part of the Zebra mussel's native range. The mussel has been accidentally introduced around the world and become an invasive species where it has been introduced.

Endemic animal species

Cyanobacteria are a phylum of picoplanktonic (plankton ranging in size from 0.2 to 2.0 µm) bacteria that obtain their energy via photosynthesis, and are present throughout the world's oceans. They exhibit a range of morphologiies, including filamentous colonies and biofilms. In the Black Sea, several species are present, and as an example, Synechococcus spp. can be found throughout the photic zone, although concentration decreases with increasing depth. Other factors which exert an influence on distribution include nutrient availability, predation and salinity.[35]
Coccolithophores are a type of motile, autotrophic phytoplankton that produce CaCO3 plates, known as coccoliths, as part of their life cycle. In the Black Sea, the main period of coccolithophore growth occurs after the bulk of the dinoflagellate growth has taken place. In May, the dinoflagellates move below the seasonal thermocline, into deeper waters, where more nutrients are available. This permits coccolithophores to utilise the nutrients in the upper waters, and by the end of May, with favourable light and temperature conditions, growth rates reach their highest. The major bloom forming species is Emiliania huxleyi, which is also responsible for the release of dimethyl sulfide into the atmosphere. Overall, coccolithophore diversity is low in the Black Sea, and although recent sediments are dominated by E. huxleyi, Braarudosphaera bigelowii, Holocene sediments have also been shown to contain Helicopondosphaera and Discolithina species.
The Black Sea is populated by many species of marine diatom, which commonly exist as colonies of unicellular, non-motile auto- and heterotrophic algae. The life-cycle of most diatoms can be described as 'boom and bust' and the Black Sea is no exception, with diatom blooms occurring in surface waters throughout the year, most reliably during March.[28] In simple terms, the phase of rapid population growth in diatoms is caused by the in-wash of silicon-bearing terrestrial sediments, and when the supply of silicon is exhausted, the diatoms begin to sink out of the photic zone and produce resting cysts. Additional factors such as predation by zooplankton and ammonium-based regenerated production also have a role to play in the annual diatom cycle.[28][29] Typically, Proboscia alata blooms during spring and Pseudosolenia calcar-avis blooms during the autumn.[32]
Annual dinoflagellate distribution is defined by an extended bloom period in subsurface waters during the late spring and summer. In November, subsurface plankton production is combined with surface production, due to vertical mixing of water masses and nutrients such as endemic dinoflagellate species in the Black Sea.[34]

The main phytoplankton groups present in the Black Sea are dinoflagellates, diatoms, coccolithophores and cyanobacteria. Generally, the annual cycle of phytoplankton development comprises significant diatom and dinoflagellate-dominated spring production, followed by a weaker mixed assemblage of community development below the seasonal thermocline during summer months and a surface-intensified autumn production.[29][31] This pattern of productivity is also augmented by an Emiliania huxleyi bloom during the late spring and summer months.

Phytoplankton blooms and plumes of sediment form the bright blue swirls that ring the Black Sea in this 2004 image.


[30] Day length and [29] During winter, strong wind promotes convective overturning and upwelling of nutrients, while high summer temperatures result in a marked vertical stratification and a warm, shallow mixed layer.

The Black Sea supports an active and dynamic marine ecosystem, dominated by species suited to the brackish, nutrient-rich, conditions. As with all marine food webs, the Black Sea features a range of trophic groups, with autotrophic algae, including diatoms and dinoflagellates, acting as primary producers. The fluvial systems draining Eurasia and central Europe introduce large volumes of sediment and dissolved nutrients into the Black Sea, but distribution of these nutrients is controlled by the degree of physiochemical stratification, which is, in turn, dictated by seasonal physiographic development.[28]

The port of Poti, Georgia


There have been isolated reports of flares on the Black Sea occurring during thunderstorms, possibly caused by lighting igniting combustible gas seeping up from the lake depths. [27]

Modelling shows the release of the hydrogen sulphide clouds in the event of an asteroid impact into the Black Sea would pose a threat to health—or even life—for people living on the Black Sea coast.[26]

Organic matter, including sapropels. Scientists have reported an annual phytoplankton bloom that can be seen in many NASA images of the region.[25] As a result of these characteristics the Black Sea has gained interest from the field of marine archaeology as ancient shipwrecks in excellent states of preservation have been discovered, such as the Byzantine wreck Sinop D, located in the anoxic layer off the coast of Sinop, Turkey.


Below the pycnocline is the Deep Water mass, where salinity increases to 22.3 psu and temperatures rise to around 8.9°C.[21] The hydrochemical environment shifts from oxygenated to anoxic, as bacterial decomposition of sunken biomass utilizes all of the free oxygen. Weak geothermal heating and long residence time create a very thick convective bottom layer.[24]

Beneath the surface waters—from about 50–100 meters—there exists a halocline that stops at the Cold Intermediate Layer (CIL). This layer is composed of cool, salty surface waters, which are the result of localized atmospheric cooling and decreased fluvial input during the winter months. It is the remnant of the winter surface mixed layer.[21] The base of the CIL is marked by a major pycnocline at about 100–200 m (330–660 feet) and this density disparity is the major mechanism for isolation of the deep water.

Outside of the Rim Current, numerous quasi-permanent coastal eddies are formed as a result of upwelling around the coastal apron and ‘wind curl’ mechanisms. The intra-annual strength of these features is controlled by seasonal atmospheric and fluvial variations. During the spring, the Batumi eddy forms in the southeastern corner of the sea.[24]

Mean surface circulation is cyclonic and waters around the perimeter of the Black Sea circulate in a basin-wide shelfbreak eddies in the summer and autumn. Mesoscale activity in the peripheral flow becomes more pronounced during these warmer seasons and is subject to interannual variability .

Because of the narrowness and shallowness of the Bosphorus and Dardanelles (their respective depths are only 33 and 70 meters), inflow and outflow current speeds are high and there is significant vertical shear. This allows for turbulent mixing of the two layers.[21] Surface water leaves the Black Sea with a salinity of 17 psu and reaches the Mediterranean with a salinity of 34 psu. Likewise, inflow of the Mediterranean with salinity 38.5 psu experiences a decrease to about 34 psu.[21]

The Black Sea only experiences water transfer with the Mediterranean Sea, so all inflow and outflow occurs in the Bosphorus and Dardanelles. Inflow from the Mediterranean has a higher salinity and density than the outflow, creating the classical estuarine circulation. This means that inflow of dense water from Mediterranean occurs at the bottom of the basin while outflow of fresher Black Sea surface-water into the Marmara Sea occurs near the surface. Fresher surface water is the product of the fluvial inputs, and this makes the Black Sea a positive sea. The net input of freshwater creates an outflow volume about twice that of the inflow. Evaporation and precipitation are roughly equal at about 300 km3/year.[21]

The Black Sea is a marginal sea [21] and is the world’s largest body of water with a meromictic basin.[22] The deep waters do not mix with the upper layers of water that receive oxygen from the atmosphere. As a result, over 90% of the deeper Black Sea volume is anoxic water.[23] The Black Sea’s circulation patterns are primarily controlled by basin topography and fluvial inputs, which result in a strongly stratified vertical structure. Because of the extreme stratification, it is classified as a salt wedge estuary.

This SeaWiFS view reveals the colourful interplay of currents on the sea’s surface.


The area surrounding the Black Sea is commonly referred to as the Black Sea Region. Its northern part lies within the Chernozem belt (black soil belt) which goes from eastern Croatia (Slavonia), along the Danube (northern Serbia, northern Bulgaria (Danubian Plain) and southern Romania (Wallachian Plain)) to northeast Ukraine and further across the Central Black Earth Region and southern Russia into Siberia.[20]

The littoral zone of the Black Sea is often referred to as the Pontic littoral or Pontic zone.[19]

The modern basin is divided into two sub-basins by a convexity extending south from the Euxine abyssal plain in the centre of the Black Sea reaches a maximum depth of 2,212 metres (7,257.22 feet) just south of Yalta on the Crimean Peninsula.[18]

The ongoing collision between the Eurasian and African plates and westward escape of the Anatolian block along the North Anatolian Fault and East Anatolian Faults dictates the current tectonic regime,[16] which features enhanced subsidence in the Black Sea basin and significant volcanic activity in the Anatolian region.[17] It is these geological mechanisms which, in the long term, have caused the periodic isolations of the Black Sea from the rest of the global ocean system.

The geological origins of the basin can be traced back to two distinct relict back-arc basins which were initiated by the splitting of an Albian volcanic arc and the subduction of both the Paleo- and Neo-Tethys Oceans, but the timings of these events remain controversial.[14][15] Since its initiation, compressional tectonic environments led to subsidence in the basin, interspersed with extensional phases resulting in large-scale volcanism and numerous orogenies, causing the uplift of the Greater Caucasus, Pontides, Southern Crimean Peninsula and Balkanides mountain ranges.[16]

The bay of Sudak, Crimea

Geology and bathymetry

English-language writers of the 18th century often used the name "Euxine Sea" ( or ) to refer to the Black Sea. Edward Gibbon, for instance, calls the sea by this name throughout The History of the Decline and Fall of the Roman Empire.[13]

A map of Asia dating to 1570, entitled "Asiae Nova Descriptio", from Abraham Ortelius's Theatrum Orbis Terrarum, labels the sea Mar Maggior ("Great Sea", cf. Latin mare major).

It is also possible that the name Axinos arose by popular etymology from a Scythian word axšaina- "unlit", "dark"; the designation "Black Sea" may thus date from Antiquity.

Strabo (7.3.6) thinks that the Black Sea was called "inhospitable" before Greek colonization because it was difficult to navigate, and because its shores were inhabited by savage tribes. The name was changed to "hospitable" after the Milesians had colonized the southern shoreline, the Pontus, making it part of Greek civilization.

Strabo's Geographica (1.2.10) reports that in antiquity, the Black Sea was often just called "the Sea" (ho pontos). For the most part, Graeco-Roman tradition refers to the Black Sea as the "Hospitable sea", Euxinos Pontos (Εὔξεινος Πόντος). This is a euphemism replacing an earlier "Inhospitable Sea", Pontos Axinos, first attested in Pindar (c. 475 BC).

Historical names

The Black Sea is one of four seas named in English after common color terms—the others being the Red Sea, the White Sea and the Yellow Sea.

  • Greek: Euxinos Pontos (Eύξεινος Πόντος)

In Greece, the historical name "Euxine Sea", which holds a different meaning (see below), is still widely used:

Such names have not yet been shown conclusively to predate the 12th century, but there are indications that they may be considerably older.

  • Abkhaz: Amshyn Eikʷa (Амшын Еиқәа)
  • Adyghe: Khy Shʼutsʼ (Хы ШӀуцӀ)
  • Bulgarian: Cherno more (Черно море, IPA: )
  • (შავი ზღვა) Shavi zghva
  • Laz: Ucha zuğa (უჩა ზუღა), or simply Zuğa "Sea"
  • Romanian: Marea Neagră (pronounced  ( ))
  • Russian: Chornoye morye (Чёрное мо́рe, IPA: 
  • Turkish: Karadeniz (IPA: )
  • Ukrainian: Chorne more (Чорне море, IPA: )
  • Kalmyk Mongolian: Khar Tengis (Хар Тэнгис or Black Sea)

Current names of the sea are usually equivalents of the English name "Black Sea", including these given in the countries bordering the sea:[12]

Modern names

The estuary of the Veleka in the Black Sea. Longshore drift has deposited sediment along the shoreline which has led to the formation of a spit, Sinemorets, Bulgaria
Sunset on the Black Sea at Laspi, Crimea


Most populous urban areas along the Black Sea coastline


Rank City Country Region/County Population (urban)


1 Istanbul Turkey Istanbul 13,624,240[6]
2 Odessa Ukraine Odessa 1,003,705
3 Samsun Turkey Samsun 535,401[7]
4 Varna Bulgaria Varna 474,076
5 Sevastopol Russia/Ukraine[8] national-level municipality on the Crimean Peninsula 379,200
6 Sochi Russia Krasnodar Krai 343,334
7 Trabzon Turkey Trabzon 305,231[9]
8 Constanța Romania Constanța 283,872[10]
9 Novorossiysk Russia Krasnodar Krai 241,952
10 Burgas Bulgaria Burgas 223,902[11]


In the Kertch Strait. A line joining Cape Takil and Cape Panaghia (45°02'N).
On the Southwest. The Northeastern limit of the Sea of Marmara [A line joining Cape Rumili with Cape Anatoli (41°13'N)].


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