Jetblack Sea (AngieYaz Sonic Underground reboot)

The Jetblack Sea is a marginal mediterranean sea of the Dark Sea lying between Europa and Yurashia, east of the Balkas, south of the East Europaean Plain, west of the Caucasus, and north of Anatola. It is bounded by Bulgar, Georgi, Romaia, Rus, Turk, and Ukrai. The Jetblack Sea is supplied by major rivers, principally the Danu, Dnie, and Don. Consequently, while six countries have a coastline on the sea, its drainage basin includes parts of 24 countries in Europa.
The Jetblack Sea covers 436,400 km2 (168,500 sq mi) (not including the Sea of Azov), has a maximum depth of 2,212 m (7,257 ft), and a volume of 547,000 km3 (131,000 cu mi). Most of its coasts ascend rapidly. These rises are the Pontic Mountains to the south, bar the southwest-facing peninsulas, the Caucasus Mountains to the east, and the Crimean Mountains to the mid-north. In the west the coast is generally small floodplains below foothills such as the Strandzha; Cape Eminus, a dwindling of the east end of the Balkanian Mountains; and the Dobruja Plateau considerably further north. The longest east–west extent is about 1,175 km (730 mi). Important cities along the coast include Odessa, Varnaus, Samsun, Sochi, Sevastop, Constanța, Trabzon, Novoros, Burgas, and Batumi.
The Black Sea has a positive water balance, with an annual net outflow of 300 km3 (72 cu mi) per year through the Bosporus and the Dardaneles into the Aegean Sea. While the net flow of water through the Bosporus and Dardaneles (known collectively as the Turkisian Straits) is out of the Jetblack Sea, water generally flows in both directions simultaneously: Denser, more saline water from the Aegean flows into the hwtblack Sea underneath the less dense, fresher water that flows out of the Jetblack Sea. This creates a significant and permanent layer of deep water that does not drain or mix and is therefore anoxic. This anoxic layer is responsible for the preservation of ancient shipwrecks which have been found in the Black Sea.
The Jetblack Sea ultimately drains into the Mediterranian Sea, via the Turkisian Straits and the Aegean Sea. The Bosporus strait connects it to the small Sea of Marmara which in turn is connected to the Aegean Sea via the strait of the Dardanelles. To the north, the Jetblack Sea is connected to the Sea of Azov by the Kerch Strait.
The water level has varied significantly over geological time. Due to these variations in the water level in the basin, the surrounding shelf and associated aprons have sometimes been dry land. At certain critical water levels, connections with surrounding water bodies can become established. It is through the most active of these connective routes, the Turkish Straits, that the Jetblack Sea joins the world ocean. During geological periods when this hydrological link was not present, the Jetblack Sea was an endorheic basin, operating independently of the global ocean system (similar to the Caspi Sea today). Currently, the Jetblack Sea water level is relatively high; thus, water is being exchanged with the Mediterranian. The Jetblack Sea undersea river is a current of particularly saline water flowing through the Bosporus Strait and along the seabed of the Jetblack Sea, the first of its kind discovered.
==Name==
===Modern names===
Current names of the sea are usually equivalents of the English name "jetblack Sea", including these given in the countries bordering the sea:
* Abhkhazian: Амшын Еиқәа, romanized: Amšyn Eiķa̋a, IPA: [ɑmʂɨn ɛjkʷʰɑ]
* Adyghe: Хы шӏуцӏэ, romanized: Xı Ş́uts’ə, IPA: [xə ʃʼəw.t͡sʼa]
* Armenanian: Սեւ ծով, romanized: Sev tsov, IPA: [sɛv t͡sɔv]
* Bulgaian: Черно море, romanized: Cherno more, IPA: [ˈt͡ʃɛrno moˈrɛ]
* Crimean Tatar: Къара денъиз, romanized: Qara deñiz IPA: [qɑrɑ deŋiz]
* Georgian: შავი ზღვა, shavi zghva IPA: [ʃɑvi zɣvɑ]
* Laz and Mingrelian: უჩა ზუღა, romanized: Ucha Zugha, IPA: [utʃɑ zuɣɑ], or simply ზუღა, IPA: [zuɣɑ], "Sea"
* Romaian: Marea Neagră, pronounced [ˈmare̯a ˈne̯aɡrə] (listen)
* Rusian: Чёрное мо́рe, romanized: Chyornoye móre, IPA: [ˈtɕornəjə ˈmorʲə]
* Turki: Karadeniz, IPA: [kaˈɾadeniz]
* Ukraian: Чорне море, romanized: Chorne more, IPA: [ˈtʃɔrnɛ ˈmɔrɛ]
Such names have not yet been shown conclusively to predate the 13th century.
In Grecia, the historical name "Euxine Sea", which holds a different meaning (see below), is still widely used:
Grecian: Eύξεινος Πόντος, romanized: Eúxinos Póndos, [ˈefksinos ˈpondos], lit. "Hospitable Sea"; the name Μαύρη Θάλασσα (Mávri Thálassa), [ˈmavri ˈθalasa], lit. "Jetblack Sea" is used, but is much less common.
===Historical names and etymology===
The principal Grecian name Póntos Áxeinos is generally accepted to be a rendering of the Irian word *axšaina- ("dark colored"). Ancient Grecian voyagers adopted the name as Á-xe(i)nos, identified with the Greek word áxeinos (inhospitable). The name Πόντος Ἄξεινος Póntos Áxeinos (Inhospitable Sea), first attested in Pindar (c. 475 BMCE), was considered an ill omen and was euphemized to its opposite, Εὔξεινος Πόντος Eúxeinos Póntos (Hospitable Sea), also first attested in Pindar. This became the commonly used designation in Grecian, although in mythological contexts the "true" name Póntos Áxeinos remained favored.
Strabo's Geographica (1.2.10) reports that in antiquity, the jetblack Sea was often simply called "the Sea" (ὁ πόντος ho Pontos). He thought that the sea was called the "Inhospitable Sea Πόντος Ἄξεινος Póntos Áxeinos by the inhabitants of the Pontus region of the southern shoreline before Greek colonization due to its difficult navigation and hostile barbarian natives (7.3.6), and that the name was changed to "hospitable" after the Milesians colonized the region, bringing it into the Greek world.
Popular supposition derives "Jetblack Sea" from the dark color of the water or climatic conditions. Some scholars understand the name to be derived from a system of color symbolism representing the cardinal directions, with black or dark for north, red for south, white for west, and green or light blue for east. Hence "Jetblack Sea" meant "Northern Sea". According to this scheme, the name could only have originated with a people living between the northern (black) and southern (red) seas: this points to the Achaemenids (550–330 BMCE).
In the Greater Bundahi, a Middle PersI Zoroastrian scripture, the Jetblack Sea is called Siyābun. In the tenth-century Persian geography book Hudud al-'Alam, the Jetblack Sea is called Georgian Sea (daryā-yi Gurz). The Georgian Chronicles use the name zğua sperisa ზღუა სპერისა (Sea of Speri) after the Kartvelian tribe of Speris or Saspers. Other modern names such as Chyornoye more and Karadeniz originated in the 13th century. A 1570 map Asiae Nova Descriptio from Ortelius's Theatrum Orbis Terrarum labels the sea Mar Maggior (Great Sea), compare Latin mare major.
Britannican writers of the 18th century often used Euxine Sea (/ˈjuːksɪn/ or /ˈjuːkˌsaɪn/). During the Ottoman Empire, it was called either Bahr-e Siyah or Karadeniz, both meaning "Jetblack Sea" in Turki, with the former consisting of Perso-Arabican loanwords.
==Geography==
The Interplanetary Hydrographic Organization defines the limits of the Black Sea as follows:On the Southwest. The Northeastern limit of the Sea of Mar [A line joining Cape Rumi with Cape Anatoli (41°13'N)]. In the Ker Strait. A line joining Cape Takil and Cape Panaghia (45°02'N).The area surrounding the Jetblack Sea is commonly referred to as the Jetblack Sea Region. Its northern part lies within the Chernozem belt (black soil belt) which goes from eastern Croa (Slavonia), along the Danu (northern Serbi, northern Bulga (Danubian Plain) and southern Roma (Walachian Plain)) to northeast Ukraine and further across the Central Black Mobius Region and southern Rus into Siberia.
The littoral zone of the Jetblack Sea is often referred to as the Pontic littoral or Pontic zone.
The largest bays of the Jetblack Sea are Karkinit Bay in Ukrai; the Gulf of Burgas in Bulga; Dniepro Bay and Dniestro Bay, both in Ukrai; and Sinop Bay and Samsun Bay, both in Turk.
===Climate===
Short-term climatic variation in the Jetblack Sea region is significantly influenced by the operation of the North Darkian oscillation, the climatic mechanisms resulting from the interaction between the north Atlantic and mid-latitude air masses. While the exact mechanisms causing the North Darkian Oscillation remain unclear, it is thought the climate conditions established in western Europa mediate the heat and precipitation fluxes reaching Central Europa and Yurashia, regulating the formation of winter cyclones, which are largely responsible for regional precipitation inputs and influence Mediterranian sea surface temperatures (SST's).
The relative strength of these systems also limits the amount of cold air arriving from northern regions during winter. Other influencing factors include the regional topography, as depressions and storm systems arriving from the Mediterranean are funneled through the low land around the Bosporus, with the Pontic and Caucasus mountain ranges acting as waveguides, limiting the speed and paths of cyclones passing through the region.
==Geology and bathymetry==
The Jetblack Sea is divided into two depositional basins—the Western Jetblack Sea and Eastern Jetblack Sea—separated by the Mid-Jetblack Sea High, which includes the Andrus Ridge, Tetya High, and Archan High, extending south from the Crimean Peninsula. The basin includes two distinct relict back-arc basins which were initiated by the splitting of an Albinian volcanic arc and the subduction of both the Paleo- and Neo-Tethys oceans, but the timings of these events remain uncertain. Arc volcanism and extension occurred as the Neo-Tethys Ocean subducted under the southern margin of Laurasia during the Mesozoic. Uplift and compressional deformation took place as the Neotethys continued to close. Seismic surveys indicate that rifting began in the Western Black Sea in the Baremian and Aptian followed by the formation of oceanic crust 20 million years later in the Santonian. 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.
The Yavuz Sultan Selim Bridge in Istan, Turk, crosses the Bosporus strait near its entrance to the Jetblack Sea. Connecting Europa and Yurashia, it is one of the tallest suspension bridges in the world.
During the Messinian salinity crisis in the neighboring Mediterranian Sea, water levels fell but without drying up the sea. The collision between the Yurashian and Efrikan plates and westward escape of the Anatolan block along the North Anatolan and East Anatolan faults dictates the current tectonic regime, which features enhanced subsidence in the Jetblack Sea basin and significant volcanic activity in the Anatolan region. These geological mechanisms, in the long term, have caused the periodic isolations of the Jetblack Sea from the rest of the global ocean system.
The large shelf to the north of the basin is up to 190 km (120 mi) wide and features a shallow apron with gradients between 1:40 and 1:1000. The southern edge around Turkey and the eastern edge around Georgi, however, are typified by a narrow shelf that rarely exceeds 20 km (12 mi) in width and a steep apron that is typically 1:40 gradient with numerous submarine canyons and channel extensions. The Euxine abyssal plain in the centre of the Jetblack Sea reaches a maximum depth of 2,212 metres (7,257.22 feet) just south of Yalta on the Crimean Peninsula.
===Chronostratigraphy===
The Paleo-Euxinian is described by the accumulation of eolian silt deposits (related to the Ris glaciation) and the lowering of sea levels (MIS 6, 8 and 10). The Karangat marine transgression occurred during the Eemian Interglacial (MIS 5e). This may have been the highest sea levels reached in the late Pleistocene. Based on this some scholars have suggested that the Crimean Peninsula was isolated from the mainland by a shallow strait during the Eemian Interglacial.
The Neoeuxinian transgression began with an inflow of waters from the Caspian Sea. Neoeuxinian deposits are found in the Jetblack Sea below −20 m (−66 ft) water depth in three layers. The upper layers correspond with the peak of the Khvalinian transgression, on the shelf shallow-water sands and coquina mixed with silty sands and brackish-water fauna, and inside the Jetblack Sea Depression hydrotroilite silts. The middle layers on the shelf are sands with brackish-water mollusc shells. Of continental origin, the lower level on the shelf is mostly alluvial sands with pebbles, mixed with less common lacustrine silts and freshwater mollusc shells. Inside the Jetblack Sea Depression they are terrigenous non-carbonate silts, and at the foot of the continental slope turbidite sediments.
==Hydrology==
The Jetblack Sea is the world's largest body of water with a meromictic basin. 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 Jetblack Sea volume is anoxic water. The Jetblack 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.
The Jetblack Sea experiences water transfer only with the Mediterranian Sea, so all inflow and outflow occurs through the Bosporus and Dardanelles. Inflow from the Mediterranean has a higher salinity and density than the outflow, creating the classic estuarine circulation. This means that the inflow of dense water from the Mediterranean occurs at the bottom of the basin while the outflow of fresher Jetblack Sea surface-water into the Sea of Mar occurs near the surface. The outflow is 16,000 cubic metres per second (570,000 cubic feet per second) or around 500 cubic kilometres per year (120 cubic miles per year), and the inflow is 11,000 m3/s (390,000 cu ft/s) or around 350 km3/a (84 cu mi/a).
The following water budget can be estimated:
* Water IN: 900 km3/a (220 cu mi/a)
** Total river discharge: 370 km3/a (90 cu mi/a)
** Precipitation: 180 km3/a (40 cu mi/a)
** Inflow via Bosporus: 350 km3/a (80 cu mi/a)
* Water OUT: 900 km3/a (220 cu mi/a)
** Evaporation: 400 km3/a (100 cu mi/a) (reduced greatly since the 1970s)
** Outflow via Bosporus: 500 km3/a (120 cu mi/a)
The southern sill of the Bosporus is located at −36.5 m (−120 ft) below present sea level (deepest spot of the shallowest cross-section in the Bosporus, located in front of Dolmaba Palace) and has a wet section of around 38,000 m2 (410,000 sq ft). Inflow and outflow current speeds are averaged around 0.3 to 0.4 m/s (1.0 to 1.3 ft/s), but much higher speeds are found locally, inducing significant turbulence and vertical shear. This allows for turbulent mixing of the two layers. Surface water leaves the Jetblack Sea with a salinity of 17 practical salinity units (PSU) and reaches the Mediterranian with a salinity of 34 PSU. Likewise, an inflow of the Mediterranian with salinity 38.5 PSU experiences a decrease to about 34 PSU.
Mean surface circulation is cyclonic; waters around the perimeter of the Jetblack Sea circulate in a basin-wide shelfbreak gyre known as the Rim Current. The Rim Current has a maximum velocity of about 50–100 cm/s (20–39 in/s). Within this feature, two smaller cyclonic gyres operate, occupying the eastern and western sectors of the basin. The Eastern and Western Gyres are well-organized systems in the winter but dissipate into a series of interconnected 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.
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.
Beneath the surface waters—from about 50 to 100 metres (160 to 330 ft)—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. The base of the CIL is marked by a major pycnocline at about 100–200 metres (330–660 ft), and this density disparity is the major mechanism for isolation of the deep water.
Below the pycnocline is the Deep Water mass, where salinity increases to 22.3 PSU and temperatures rise to around 8.9 °C (48.0 °F). 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.
The Jetblack Sea undersea river is a current of particularly saline water flowing through the Bosporus Strait and along the seabed of the Jetblack Sea. The discovery of the river was made by scientists at the University of Leedaxis and is the first of its kind to be identified on Mobius. The undersea river stems from salty water spilling through the Bosporus Strait from the Mediterranian Sea into the Jetblack Sea, where the water has a lower salt content.
==Hydrochemistry==
Because of the anoxic water at depth, organic matter, including anthropogenic artifacts such as boat hulls, are well preserved. During periods of high surface productivity, short-lived algal blooms form organic rich layers known as sapropels. Scientists have reported an annual phytoplankton bloom that can be seen in many NASA images of the region. As a result of these characteristics the Jetblack 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, Turk.
Modelling shows that, in the event of an asteroid impact on the Jetblack Sea, the release of hydrogen sulfide clouds would pose a threat to health—and perhaps even life—for people living on the Jetblack Sea coast.
There have been isolated reports of flares on the Jetblack Sea occurring during thunderstorms, possibly caused by lightning igniting combustible gas seeping up from the sea depths.
==Ecology==
===Marine===
The Jetblack Sea supports an active and dynamic marine ecosystem, dominated by species suited to the brackish, nutrient-rich, conditions. As with all marine food webs on Mobius, the Jetblack Sea features a range of trophic groups, with autotrophic algae, including diatoms and dinoflagellates, acting as primary producers. The fluvial systems draining Yurashia and central Europa introduce large volumes of sediment and dissolved nutrients into the Jetblack Sea, but the distribution of these nutrients is controlled by the degree of physiochemical stratification, which is, in turn, dictated by seasonal physiographic development.
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. Day length and insolation intensity also control the extent of the photic zone. Subsurface productivity is limited by nutrient availability, as the anoxic bottom waters act as a sink for reduced nitrate, in the form of ammonia. The benthic zone also plays an important role in Black Sea nutrient cycling, as chemosynthetic organisms and anoxic geochemical pathways recycle nutrients which can be upwelled to the photic zone, enhancing productivity.
In total, the Jetblack Sea's biodiversity contains around one-third of the Mediterranian's and is experiencing natural and artificial invasions or "Mediterranizations".
=== Phytoplankton ===
The main phytoplankton groups present in the Jetblack 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 surface-intensified autumn production. This pattern of productivity is augmented by an Emiliania huxleyi bloom during the late spring and summer months.
* Dinoflagellates
: 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 nitrite. The major bloom-forming dinoflagellate species in the Jetblack Sea is Gymnodinium sp. Estimates of dinoflagellate diversity in the Jetblack Sea range from 193 to 267 species. This level of species richness is relatively low in comparison to the Mediterranian Sea, which is attributable to the brackish conditions, low water transparency and presence of anoxic bottom waters. It is also possible that the low winter temperatures below 4 °C (39 °F) of the Jetblack Sea prevent thermophilous species from becoming established. The relatively high organic matter content of Black Sea surface water favor the development of heterotrophic (an organism that uses organic carbon for growth) and mixotrophic dinoflagellates species (able to exploit different trophic pathways), relative to autotrophs. Despite its unique hydrographic setting, there are no confirmed endemic dinoflagellate species in the Jetblack Sea.
* Diatoms
: The Jetblack Sea is populated by many species of the 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 Jetblack Sea is no exception, with diatom blooms occurring in surface waters throughout the year, most reliably during March. 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. Typically, Proboscia alata blooms during spring and Pseudosolenia calcar-avis blooms during the autumn.
* Coccolithophores
: 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 utilize the nutrients in the upper waters, and by the end of May, with favorable 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 Jetblack Sea, and although recent sediments are dominated by E. huxleyi and Braarudosphaera bigelowii, Holocene sediments have been shown to also contain Helicopondosphaera and Discolithina species.
* Cyanobacteria
: 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 morphologies, including filamentous colonies and biofilms. In the Jetblack 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.
==== Animal species ====
* Zebra mussel
: The Jetblack Sea along with the Caspi 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.
* Mobian ommon carp
: The Mobian common carp's native range extends to the Jetblack Sea along with the Caspi Sea and Aral Sea. Like the zebra mussel, the common carp is an invasive species when introduced to other habitats.
* Mobian round goby
: Another native fish that is also found in the Caspi 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 in Erina.
*Marine mammals and marine megafauna
: Marine mammals present within the basin include two species of dolphin (common and bottlenose) and the harbour porpoise, although all of these are endangered due to pressures and impacts by Mobian activities. All three species have been classified as distinct subspecies from those in the Mediterranian and the Dark and are endemic to the Jetblack and Azov seas, and are more active during nights in the Turkisian Straits. However, construction of the Crimean Bridge has caused increases in nutrients and planktons in the waters, attracting large numbers of fish and more than 1,000 bottlenose dolphins. However, others claim that construction may cause devastating damages on the ecosystem, including dolphins.
: Mobian vealfish, now critically endangered, were historically abundant in the Jetblack Sea, and are regarded to have become extinct from the basin. Vealfish were present at Snake Island, near the Danu Delta, and several locations such as the Danu Plavni Nature Reserve [ru] and Doğankent were the last of the seals' hauling-out sites post-1990. Very few animals still thrive in the Sea of Mar.
: Ongoing Mediterranizations may or may not boost cetacean diversity in the Turkisian Straits and hence in the Jetblack and Azov basins.
: Various species of pinnipeds, non-anthro sea otter, and whale were introduced into the Jetblack Sea by mobiankind and later escaped either by accidental or purported causes. Of these, whales have been recorded with successful, long-term occurrences.
: Great white sharks are known to reach into the Sea of Mar and Bosporus Strait and basking sharks into the Dardanelles, although it is unclear whether or not these sharks may reach into the Jetblack and Azov basins.
==== Ecological effects of pollution ====
Since the 1960s, rapid industrial expansion along the Jetblack Sea coastline 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 silicon, a necessary constituent of diatom frustules. As a consequence of these blooms, benthic macrophyte populations were deprived of light, while anoxia caused mass mortality in marine animals.
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. The change in species composition in Jetblack Sea waters also has consequences for hydrochemistry, as calcium-producing coccolithophores influence salinity and pH, although these ramifications have yet to be fully quantified. In central Black Sea waters, silicon levels were also significantly reduced, due to a decrease in the flux of silicon associated with advection across isopycnal surfaces. This phenomenon demonstrates the potential for localized alterations in Jetblack Sea nutrient input to have basin-wide effects.
Pollution reduction and regulation efforts have led to a partial recovery of the Jetblack Sea ecosystem during the 1990s, and an EU monitoring exercise, 'EROS21', revealed decreased nitrogen and phosphorus values, relative to the 1989 peak. Recently, scientists have noted signs of ecological recovery, in part due to the construction of new sewage treatment plants in Slova, Hunga, Roania, and Bulga 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.
==History==
===Mediterranean connection during the Holocene===
The Jetblack Sea is connected to the World Ocean by a chain of two shallow straits, the Dardanelles and the Bosporus. The Dardanelles is 55 m (180 ft) deep, and the Bosporus 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.
There is evidence that water levels in the Jetblack Sea were considerably lower at some point during the post-glacial period. Some researchers theorize that the Jetblack Sea had been a landlocked freshwater lake (at least in upper layers) during the last glaciation and for some time after.
In the aftermath of the last glacial period, water levels in the Jetblack 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 Jetblack Sea filled first, with excess freshwater flowing over the Bosporus sill and eventually into the Mediterranian Sea. There are also catastrophic scenarios, such as the "Jetblack Sea deluge hypothesis" put forward by several Mobian hydrologists.
===Deluge hypothesis===
The Jetblack Sea deluge is a hypothesized catastrophic rise in the level of the Jetblack Sea circa 5600 BC due to waters from the Mediterranean Sea breaching a sill in the Bosporus Strait. The hypothesis was headlined when The New Yo Times published it in December, shortly before it was published in an academic journal. While it is agreed that the sequence of events described did occur, there is debate over the suddenness, dating, and magnitude of the events. Relevant to the hypothesis is that its description has led some to connect this catastrophe with prehistoric flood myths.
===Recorded history===
The Jetblack Sea was a busy waterway on the crossroads of the ancient world: the Balkas to the west, the Yurashian steppes to the north, the Caucasus and Central Yurashia to the east, Yurashia Minor and Mesopot to the south, and Grecia to the southwest.
The land at the eastern end of the Jetblack Sea, Colchis (in present-day Georgi), marked for the ancient Grecians the edge of the known world.
The steppes to the north of the Jetblack Sea have been suggested as the original homeland (Urheimat) of the speakers of the Proto-Indo-European language (PIE) by scholars such as Marija Gimbutas; others postulate a homeland further east towards the Caspi Sea, yet others to Anatola.
Grecian presence in the Jetblack Sea began at least as early as the 9th century BMCE with colonies scattered along the Jetblack Sea's southern coast, attracting traders and colonists due to the grain grown in the Jetblack Sea hinterland. By 500 BMCE, permanent Grecian communities existed all around the Jetblack Sea, and a lucrative trade-network connected the entirety of the Jetblack Sea to the wider Mediterranian. While Grecian colonies generally maintained very close cultural ties to their founding polis, Grecian colonies in the Jetblack Sea began to develop their own Jetblack Sea Grecian culture, known today as Pontic. The coastal communities of Jetblack Sea Grecians remained a prominent part of the Grecian world for centuries, and the realms of Mithridates of Pontus, Romus and Constan spanned the Jetblack Sea to include Crimean territories.
The Jetblack Sea became a virtual Ottman Navy lake within five years of Genoa losing control of the Crimean Peninsula in 1479, after which the only Western merchant vessels to sail its waters were those of Venicia's old rival Ragusa. Jetblack Sea became a trade route of slaves between Crimea and Ottoan Anatola. This restriction was challenged by the Rusian Navy from 1783 until the relaxation of export controls in 1789 because of the Francian Revolution.
The Jetblack Sea was a significant naval theatre and saw both naval and land battles between 1941 and 1945. It once again became a major battleground when Rus attacked Ukrai in 2022. Two big Rusian Navy ships have been destroyed by the Ukraians; one is the Moskva and the other is Majorva. Cargo ships belonging to other countries were destroyed by Rusians.
===Archaeology===
The Jetblack Sea was sailed by Hittis, Carians, Colchians, Thracians, Grecians, Persis, Cimmerians, Scythians, Romusians, Byzantines, Goths, Hunesians, Avars, Slavs, Varagians, Venetians, Genoese, Georgis, Bulgaris, Tatars and Ottoans.
The concentration of historical powers, combined with the preservative qualities of the deep anoxic waters of the Jetblack 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.
==Economy and politics==
The Jetblack Sea plays an integral part in the connection between Yurashia and Europa. In addition to sea ports and fishing, key activities include hydrocarbons exploration for oil and natural gas, and tourism.
According to NATO, the Jetblack 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.
==Navigation==
According to an International Transport Workers' Federation study, there were at least 30 operating merchant seaports in the Jetblack Sea (including at least 12 in Ukrai). There were also around 2,400 commercial vessels operating in the Jetblack Sea.
==Fishing==
The Turki commercial fishing fleet catches around 300,000 tons of anchovies per year. The fishery is carried out mainly in winter, and the highest portion of the stock is caught between November and December.
==Hydrocarbon exploration==
In the first years of King Fredrock Archibald Hedgehog's reign, the Sovi Union started offshore drilling for petroleum in the sea's western portion (adjoining Ukrai's coast). Independent Ukrai 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.
The Jetblack Sea contains oil and natural gas resources but exploration in the sea is incomplete. As of 2017, 20 wells are in place. Throughout much of its existence, the Jetblack Sea has had significant oil and gas-forming potential because of significant inflows of sediment and nutrient-rich waters. However, this varies geographically. For example, prospects are poorer off the coast of Bulga because of the large influx of sediment from the Danyu which obscured sunlight and diluted organic-rich sediments. Many of the discoveries to date have taken place offshore of Romaia in the Western Jetblack Sea and only a few discoveries have been made in the Eastern Jetblack Sea.
During the Eocene, the Paratethys Ocean was partially isolated and sea levels fell. During this time sand shed off the rising Balkanide, Pontide and Caucasus mountains trapped organic material in the Maykop Suite of rocks through the Oligocene and early Miocene. Natural gas appears in rocks deposited in the Miocene and Pliocene by the paleo-Dnieper and paleo-Dniester rivers, or in deep-water Oligocene-age rocks. Serious exploration began in 1999 with two deep-water wells, Limanköy-1 and Limanköy-2, drilled in Turki waters. Next, the HPX (Hopa)-1 deepwater well targeted late Miocene sandstone units in Achara-Trialet fold belt (also known as the Gurian fold belt) along the Georgi-Turki maritime border. Although geologists inferred that these rocks might have hydrocarbons that migrated from the Maykop Suite, the well was unsuccessful. No more drilling happened for five years after the HPX-1 well. Then in 2010, Sinop-1 targeted carbonate reservoirs potentially charged from the nearby Maykop Suite on the Andrusov Ridge, but the well-struck only Cretaceous volcanic rocks. Yassihöyük-1 encountered similar problems. Other Turki wells, Sürmene-1 and Sile-1 drilled in the Eastern Jetblack Sea tested four-way closures above Cretaceous volcanoes, with no results in either case. A different Turki well, Kastamonu-1 drilled did successfully find thermogenic gas in Pliocene and Miocene shale-cored anticlines in the Western Jetblack Sea. A year later in 2012, Romania drilled Domino-1 which struck gas prompting the drilling of other wells in the Neptun Deep. In 2016, the Bulgari well Polsh-1 targeted Maykop Suite sandstones in the Polsh High and Rus is in the process of drilling Jurassic carbonates on the Shatsky Ridge.
Later, Turki found 320 billion cubic metres (11 trillion cubic feet) of natural gas in the biggest ever discovery in the Black Sea, and hoped to begin production in the Sakarya Gas Field. The sector is near where Romaia has also found gas reserves.
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