The aral sea

THE ARAL SEA

Plan:

1Formation

2Ecology

2.1Native fish

2.2Introduced fish

2.3Invertebrates

3History

3.1Naval

3.2Irrigation canals

4Impact on environment, economy, and public health

4.1Biology

The Aral Sea (/ˈærəl/ ARR-əl; Kazakh: Арал теңізі, romanized: Aral teńizi; Uzbek: Орол денгизи, romanized: Orol dengizi; Karakalpak: Арал теңизи, romanized: Aral ten'izi; Russian: Аральское море, romanized: Aral'skoye more) was an endorheic lake lying between Kazakhstan (Aktobe and Kyzylorda Regions) in the north and Uzbekistan (Karakalpakstan autonomous region) in the south which began shrinking in the 1960s and had largely dried up by the 2010s. The name roughly translates as "Sea of Islands", referring to over 1,100 islands that had dotted its waters. In the Mongolic and Turkic languages aral means "island, archipelago". The Aral Sea drainage basin encompasses Uzbekistan and parts of Tajikistan, Turkmenistan, Kyrgyzstan, Kazakhstan, Afghanistan, and Iran.

Formerly the fourth largest lake in the world with an area of 68,000 km2 (26,300 sq mi), the Aral Sea began shrinking in the 1960s after the rivers that fed it were diverted by Soviet irrigation projects. By 1997, 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 an ongoing effort in Kazakhstan to save and replenish the North Aral Sea, the Dike Kokaral dam was completed in 2005. By 2008, the water level had risen 12 m (39 ft) above that of 2003. Salinity has dropped, and fish are again present in sufficient numbers for some fishing to be viable. The maximum depth of the North Aral Sea was 42 m (138 ft) (as of 2008).

The shrinking of the Aral Sea has been called "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 two million hectares (5,000,000 acres) 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

The Syr Darya sturgeon (Pseudoscaphirhynchus fedtschenkoi) was a primitive species of fish possibly driven to extinction by the shrinkage of the Aral Sea.

The Ukrainian stickleback (Pungitius platygaster) was the only native species of the Aral Sea to survive its reduction and salinization.

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 (as well as the three endemic sturgeon species), most of which still survive in the North Aral Sea, but some such as the sturgeons have been extirpated or even driven extinct by the lake's shrinkage. Native fish species of the lake included ship sturgeon (Acipenser nudiventris), all three Pseudoscaphirhynchus sturgeon species, Aral trout (Salmo trutta aralensis), northern pike (Esox lucius), ide (Leuciscus idus oxianus), asp (Aspius aspius iblioides), common rudd (Scardinius erythropthalmus), Turkestan barbel (Luciobarbus capito conocephalus), Aral barbel (L. brachycephalus brachycephalus), common bream (Abramis brama orientalis), white-eyed bream (Ballerus sapa aralensis), Danube bleak (Chalcalburnus chalcoides aralensis), ziege (Pelecus cultratus), crucian carp (Carassius carassius gibelio), common carp (Cyprinus carpio aralensis), Wels catfish (Silurus glanis), Ukrainian stickleback (Pungitius platygaster aralensis), zander (Sander lucioperca), European perch (Perca fluviatilis), and Eurasian ruffe (Gymnocephalus cernuus). All these fish aside from the stickleback lived an anadramous or semi-anadromous lifestyle.

The salinity increase and drying of the lake extirpated the Aral trout, ruffe, Turkestan barbel and all sturgeon species, and dams now block their return and migration routes, with the Aral trout and Syr Darya sturgeon (Pseudoscaphirhynchus fedtschenkoi) possibly extinct due to their restricted range. All other native fish barring the stickleback (which persisted during the lake's shrinkage and salinity increase) were also extirpated, but have returned to the North Aral Sea following its recovery from the 1990s onwards.

Introduced fish

The European flounder (Platichthys flesus) was a saltwater fish introduced to the Aral Sea.

The black carp (Mylopharyngodon piceus) was a freshwater fish introduced to the Aral Sea.

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 (Clupea harengus membras), big-scale sand smelt (Atherina boyeri caspia), black-striped pipefish (Syngnatus abaster caspius), Caucasian dwarf goby (Knipowitschia caucasica), monkey goby (Neogobius fluviatilis), round goby (N. melanostomus), Syrman goby (N. syrman), bighead goby (Ponticola kessleri), tubenose goby (Proterorchinus marmoratus), grass carp (Ctenopharyngodon idella), silver carp (Hypophtalmichthys molitrix), bighead carp (H. nobilis), black carp (Mylopharyngodon piceus) and northern snakehead (Channa argus warpachowski).

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 (possibly) pipefish survived the lake's shrinkage and salinity increase, and during this time the European flounder (Platichthys flesus) was introduced to revive fisheries. The extirpated species (aside from possibly the pipefish) 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.