Aral Sea


The Aral Sea was an endorheic salt lake lying between Kazakhstan to its north and Uzbekistan to its south, which began shrinking in the 1960s and had largely dried up into desert by the 2010s. It was in the Aktobe and Kyzylorda regions of Kazakhstan and the Karakalpakstan autonomous region of Uzbekistan. The name roughly translates from Mongolic and Turkic languages to "Sea of Islands", a reference to the large number of islands that once dotted its waters. The Aral Sea drainage basin encompasses Uzbekistan and parts of Afghanistan, Iran, Kazakhstan, Kyrgyzstan, Tajikistan, and Turkmenistan.
Formerly the third-largest lake in the world with an area of, the Aral Sea began shrinking in the 1960s after the rivers that fed it were diverted by Soviet irrigation projects. By 2007, it had declined to 10% of its original size, splitting into four lakes: the North Aral Sea, the eastern and western basins of the once far larger South Aral Sea, and the smaller intermediate Barsakelmes Lake. By 2009, the southeastern lake had disappeared and the southwestern lake had retreated to a thin strip at the western edge of the former southern sea. In subsequent years occasional water flows have led to the southeastern lake sometimes being replenished to a small degree. Satellite images by NASA in August 2014 revealed that for the first time in modern history the eastern basin of the Aral Sea had completely dried up. The eastern basin is now called the Aralkum Desert.
In a Kazakhstani effort to save and replenish the North Aral Sea, the Dike Kokaral dam was completed in 2005. By 2008, the water level had risen above that of 2003, to., salinity dropped, and fish were again present in sufficient numbers for some fishing to be viable.
After the visit to Muynak in 2011, United Nations Secretary General Ban Ki-moon called the shrinking of the Aral Sea "one of the planet's worst environmental disasters". The region's once-prosperous fishing industry has been devastated, bringing unemployment and economic hardship. The water from the diverted Syr Darya river is used to irrigate about of farmland in the Ferghana Valley. The Aral Sea region is heavily polluted, with consequent serious public health problems. UNESCO has added historical documents concerning the Aral Sea to its Memory of the World Register as a resource to study the environmental tragedy.

Formation

The Amu Darya river flowed into the Caspian Sea via the Uzboy Channel until the Holocene. Geographer Nick Middleton believes it did not begin to flow into the Aral Sea until that time.

Ecology

Native fish

Despite its former vast size, the Aral Sea had relatively low indigenous biodiversity. However, the Aral Sea basin had an exceptional array of endemic fish subspecies. Most of these still survive in the North Aral Sea, but some, such as the sturgeons, have been greatly reduced or even driven to extirpation by the lake's shrinkage. Native fish species of the lake included
All these fish aside from the stickleback lived an anadramous or semi-anadromous lifestyle.
The salinity increase and drying of the lake led to the local extinction of the Aral trout, ruffe, Turkestan barbel, and all sturgeon species, and dams now block their return and migration routes; the Aral trout and Syr Darya sturgeon may be extinct due to their restricted range. All other native fish, barring the stickleback, were also extirpated, but many have returned to the North Aral Sea following its recovery from the 1990s onwards.

Introduced fish

Other salt-tolerant fish species were intentionally or inadvertently introduced during the 1960s when hydropower and irrigation projects reduced the flow of fresh water thereby increasing salinity. These include the Baltic herring, big-scale sand smelt, black-striped pipefish, Caucasian dwarf goby, monkey goby, round goby, Syrman goby, bighead goby, tubenose goby, grass carp, silver carp, bighead carp, black carp, and northern snakehead.
The herring, sand smelt, and gobies were the first planktivorous fish in the lake, leading to a collapse of the lake's zooplankton population. This in turn caused a collapse of the herring and sand smelt population from which neither species has recovered. All introduced species aside from the carp, snakehead, and pipefish survived the lake's shrinkage and salinity increase, and during this time the European flounder was introduced to revive fisheries. The extirpated species returned to the North Aral Sea following its recovery. Herring, sand smelt, gobies and flounder persisted in the South Aral Sea until increasing salinity extirpated all but the gobies.

Invertebrates

Prior to its shrinkage, the Aral Sea had about 250 species of native aquatic invertebrates, the majority being freshwater species; the rest were marine invertebrates with ties to the Ponto-Caspian and Mediterranean-Atlantic fauna. The dominant species were rotifers, cladocerans, and copepods. Advanced crustaceans were represented by a single amphipod species, Dikerogammarus aralensis, an endemic of the Syr Darya basin. There were several native bivalves in the Aral Sea, including members of the genera Dreissena, Hypanis, and the lagoon cockle . Native gastropods included Theodoxus pallasi and a member of Caspiohydrobia.
Many of these invertebrates had their numbers drastically reduced due to the introduced fish species. Later, during an unsuccessful attempt to introduce mullet to the Aral from the Caspian Sea, the rockpool shrimp was inadvertently introduced to the sea. The shrimp is thought to be responsible for the extirpation of the near-endemic amphipod Dikerogammarus aralensis, which now survives only in the Syr Darya basin. The copepod Calanipeda aquaedulcis was introduced to the Aral to replace the zooplankton species reduced by the herring population, and the North American mud crab Rhithropanopeus harrisii was inadvertently introduced during this attempt as well.
Later, as the lake's salinity increased, many of the freshwater-adapted species disappeared, only leaving behind the marine and saline species. However, the zooplankton population in the North Aral Sea has recovered as salinity has decreased from the 1990s onwards, with extirpated crustacean and rotifer species returning naturally via the Syr Darya River, at the expense of the saltwater species. The cladoceran Moina mongolica, extirpated by the introduced fish species, has also returned. The zebra mussel has been reintroduced. In contrast, in the South Aral Sea only a few nematodes, rotifers, and parthenogenic brine shrimp exist. The future prospects for aquatic invertebrates in all remaining Aral Sea fragments depend on their future changes in salinity.

History

Climate shifts have driven multiple phases of sea-level rise and fall. Inflow rates from the Amu Darya and Syr Darya are affected by glacial melt rates at the rivers' headwaters as well as precipitation within the river basins; cold, dry climates restrict both processes. Geologically driven shifts in the course of the Amu Darya between the Aral Sea and the Sarykamysh basins and anthropogenic water withdrawal from Amu Darya and Syr Darya have caused fluctuations in the Aral Sea's water level. Artificial irrigation systems began in ancient times and continue to the present. According to Sergey Tolstov's theory, once Amu Darya was connected to Caspian sea, but this connection was broken by people 2500 years ago to feed the Aral Sea and irrigation system in Khorezm, more precisely in Khiva and other cities in this region.
The Aral Sea was part of the western frontier of the Chinese Empire during the Tang dynasty.
During Mongol Invasion, Mongols destroyed the cities and waterworks, which led to changes in Amu Darya's route, or some of its branches, and refilling the Lake Sarykamysh, that connected Caspian Sea again. Aral Sea region was divided between three Mongol Hordes: the Jochi or Golden Horde, the Ilkhanids, and the Chagatai.
Muslim geographers, such as Hafiz-i Abru, wrote about the disappearance of the Aral Sea in 1417 due to diversions in both the Amu Darya and Syr Darya. The Syr Darya only resumed its natural course into the lake after 1573, when the channels that had been carved to divert its course to the south fell into disrepair. That caused the surface of the sea to steadily rise, flooding the basin for the next four centuries.
The Russian expedition of Alexey Butakov performed the first observations of the Aral Sea in 1848. The first steamer arrived in the Aral Sea three years later. The Aral Sea fishing industry began with the Russian dealers Lapshin, Ritkin, Krasilnikov, and Makeev, which later formed major fishing unions.

Naval

Russian naval presence on the Aral Sea began in 1847 with the founding of Raimsk, soon renamed Fort Aralsk, near the mouth of the Syr Darya. As the Aral Sea basin is not connected to other bodies of water, the Imperial Russian Navy deployed its vessels by disassembling them in Orenburg on the Ural River and transporting them overland to be reassembled at Aralsk. The first two ships, assembled in 1847, were the two-masted schooners Nikolai and Mikhail. The former was a warship; the latter a merchant vessel to establish fisheries. They surveyed the northern part of the sea in 1848, the same year that a larger warship, the Constantine, was assembled. Commanded by Lt. Alexey Butakov, the Constantine completed the survey of the entire Aral Sea over the next two years. Exiled Ukrainian poet and painter Taras Shevchenko participated in the expedition and produced a number of sketches.
In 1851 two newly built steamers arrived from Sweden. The geological surveys had found no coal deposits in the area so the Military Governor-General of Orenburg Vasily Perovsky ordered an "as large as possible supply" of saxaul to be collected in Aralsk for the new steamers. Saxaul wood proved not to be a suitable fuel and in the later years the Aral Flotilla was provisioned, at substantial cost, by coal from the Donbas.