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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

601: Irgyz -Turgai

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Nina Bogutskaya

Countries:

Kazakhstan; Russia

Boundaries:

This ecoregion encompasses the endorheic basins of the Irgyz and Turgai rivers, along with a number of small interconnected lakes and intermittent channels. In the west the border follows the Mugodzhary Mountains [Mughalzhar Tauy], which divides the Irgiz [Yrghyz] River from the Or’ River drainage (a tributary of the Ural [Zhayyq] River) and Emba [Zhem] River. In the north the Turgai Tableland [Turghay Ustirti] divides the headwaters of the Igriz and Turgai rivers from the Tobol (Irtysh tributary) headwaters (Ob [602]). The border crosses the Turgai Dolina Valley [Torghay Zhylghasy] and runs south along the western slopes of the Kazakhskiy Melkosopochnik Upland [Qazaqtyng Usaqshoqylyghy], which is the divide between the Tughay and Ishim drainage (Ob [602]). Further south and southeast the Ulutau Mountains [Ulytau] (western region of the Kazakhskiy Melkosopochnik Upland = Qazaqtyng Usaqshoqylyghy) forms the border between this ecoregion and the Sarysu River drainage (in the Lower and Middle Syr Darya [626]). In the south the ecoregion meets the Peski Priaral’skiy Karakumy Desert [Aral Mangy Qaraqumy] (Aral Sea Drainages [629]). The southernmost part of the ecoregion lies between the Peski Bol’shiye Barsuki Desert [Ulken Borsyq Qumi] and Chagray Plateau [Shaghyray Ustirti].

Drainages flowing into:

West Asian endorheic basin

Main rivers or other water bodies:

The main water bodies of the ecoregion include the Irgiz [Yrghyz] River, Lake Dzhalangach [Ul’ken-Zhalanash];  Lake Karasu; Turgai [Turghay] River, Karaturghay River, Ulyzhilanshik River, Ul’kayak [Olkeyek] River, Lake Chelkar-Tangiz, Saryozen River, Teke River, Sarykopa Lakes, Lake Suzhargan; Bulanty River, Beleutty River, and Lake Shubar-Tengiz.

Topography:

The Irgiz River rises in the eastern spurs of the Mugodzharskiye Mountains, and is confluent with the Turgai near its estuary. The length of the river is 180 km, and its drainage area is apporoximately 25,000 km2. The Turgai River rises on the western outskirts of the Central Kazakhstan Melkosopochnik Upland at about 450 m altitude, and falls into Lake Chelkar-Tengiz having passed through a number of lakes. An elaborate network of tributaries lies in the upper part of the basin. In the confluence they form the Kara-Turgai River, which after the confluence with the Sary-Turgai is called Turgai.

Climate:

The ecoregion is in continental and cold semi-desert climate zones. The semi-desert climate experiences an extreme contrast between summer and winter, with temperatures ranging between -13 oC and 24 oC. The mean annual daily temperature is ~10 oC. The northern part of the ecoregion is characterized by hot and dry summers and cold winters.

Freshwater habitats:

Rivers of the ecoregion are full-flowing in spring and shallow in other seasons of the year. In the upper and middle reaches the Irgiz flows through an ancient valley with well-developed terraces. Downstream from the town of Irgiz the river channel is poorly pronounced, so lakes and marshes occur in the floodplain. Upstream from the confluence with the Turgai River sandhills comprise the coasts along the river. After the spring flood the upper (up to the confluence with the Karabutak River) and lower reaches of the Irgiz split into a number of stretches separated by dried parts of the river channel. In the summer water of the Irgiz becomes brackish due to evaporation.

For much of its course the Turgai River flows through the Turgai Hollow. In this area it has a wide floodplain that is swampy in some areas. In spring the Turgai overflows and its water level rises by 4—8 m. When the floodplain overflows the river forms branches, oxbows, and numerous lakes.  The duration of flooding is 20—25 days. In summer the water level of the river declines abruptly, but a small flow is observed throughout the year.

The waters of the Turgai River and its tributaries are very diverse in terms of chemical composition. Only the upper Turgai River contains freshwater throughout the whole year. In the lower reaches, beginning from the middle of the summer, it becomes brackish. The water of the Sary-Turgai River is fresh, but it quickly becomes saline in the Kabarga and Bistamak rivers after the spring flood.

Lakes of the Irgiz-Turgai system in the southwestern part of Kazakhstan differ from each other by geological age, limnological history, hydrological and physicochemical regime, organic matter accumulation processes, specificity of food supply, and species composition of fishes.

Terrestrial Habitats:

The ecoregion comprises two terrestrial ecoregions – Kazakh semi-desert and Kazakh steppe. The Kazakh semi-desert is an ecotone between steppe in the northern part of the ecoregion and desert to the south. Much of this landscape consists of plains and melkosopochnik, dominated by bunch-grass steppes and dwarf semi-shrub deserts. Some of the rare plant species in the semi-desert include Artemisia lessingiana, Stipa richterana, Ferula feruloides, and Brachanthemum kasakorum. Kazakh steppe occurs in the northern part of the ecoregion. It is dominated by turf graminoids such as species in the genus Stipa.

Fish Fauna:

The ichtyofauna of the Irgyz – Turgai ecoregion consists of representatives of the faunal complex that forms the basis of the Arctic Province of the Circumpolar Subregion, but it is exceptionally impoverished. Less than ten native species in two families (Cyprinidae, Percidae) inhabit this ecoregion. These include ide (Leuciscus idus), common dace (L. leuciscus), roach (Rutilus rutilus), Crucian carp (Carassius carassius), Prussian carp (C. gibelio), tench (Tinca tinca), European perch (Perca fluviatilis), and ruffe (Gymnocephalus cernuus). This region, however, is possibly transitional between the Ponto-Caspian-Aral and Arctic Sea provinces. Up to now its role as a transit corridor between the basins of the Irtysh and the Aral Sea remains unclear.

There is a well-founded hypothesis that in the time of the Quaternary glaciations, when the lower part of the Ob was covered by glaciers and its waters could not flow north, in the West Siberian Lowland large lake basins were formed and waters of the Ob flowed south toward the Aral-Caspian basin through the Turgai Strait, connecting the present upper Tobol River with the Aral Sea. However, not a single species of the Caspian-Aral complex has been recorded in this ecoregion. The reason for this is unclear. At the same time the Siberian fauna is also poorly represented in the drainage of the Irgiz-Turgai, which makes one recognize the hypothesis for a relatively recent catastrophic change of hydrography of the region related to the drying of the main water bodies and populating them through the upper Ter-Sakan River (Ishim basin) and the upper tributaries of the Kara-Turgai River through chains of lakes. A thorough morphological comparison of the Irgiz-Turgai forms with the Aral and Siberian forms is needed.

Description of endemic fishes:

There are no endemic species in this ecoregion.

Ecological phenomena:

The inconsistent water level from year to year is a characteristic of the lakes of the Irgiz-Turgai system. This depends on the climate and timing of spring, and also the complete or partial drying of some lakes in dry years. Some shallow lakes (depth 3 m) become nearly completely overgrown by underwater and surface vegetation, and exhibit high hydrogen sulphide content in their ground and water. Such lakes, in a majority of which only Carassius species survive, are so-called "suffocation" or "carassius" lakes. Other deeper lakes (depth up to 5-7 m) have a sand bottom, lack massive vegetation cover on the bottom, and have low hydrogen sulphide content. These lakes contain a relatively varied composition of ichthyofauna, and are called ”pike” lakes. These lakes, apart from Carassius species, include pike, perch, ide, and sometimes, ruff.

Justification for delineation:

The ecoregion covers the endorheic basins of two rivers, Irgyz and Turgai, with a number of small interconnected lakes. It is located in a plain with numerous, almost stagnant, water bodies. Some river sections and lakes are periodically desiccated. The fauna demonstrates clear Siberian links, but is very depauperate. It is unclear why there has not been a single species of fishes of the Caspian Aral complex noted in this ecoregion. A thorough morphological comparison of the Irgiz-Turgai forms with the Aral and Siberian forms is needed to clarify the zoogeographical affinities of the ecoregion.

Level of taxonomic exploration:

Fair

References/sources:

Kozhara, A. V.,Kas'yanov, A. N. (1993). "New data to fish fauna of the Igriz-Turgai basin" Voprosy Ichthyol 33(2) 293-296.

Mitrofanov, V. P. (1961)"Fishes of Markakul Lake" In Fisheries in republics of Central Asia and Kazakhstan. (pp. 51-64) Alma-Ata:

Mitrofanov, V. P.,Dukravets, G. M. (1986). "Fishes of Kazakhstan" 1-5 Alma-Ata: Nauka.

Serov, N. P. (1961)"To ichthyogeographical position of the Igriz-Turgai basin" In Proceedings of the conference on fisheries of Central Asian republics and Kazakhstan. (pp. 213-215) Alma-Ata:

World Wildlife, Fund (2001). "Terrestrial Ecoregions of the World" 2005 (2005; www.worldwildlife.org/science/ecoregions/biomes.cfm).

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