Boundaries

The ecoregion encompasses the Severnaya Zemlya Islands and the area between the Yenisei [605] and Anabar [608] drainage divides. This includes the entire Taimyr Peninsula and the northwestern part of the Srednesibirskoye Ploskogor’ye Upland. The divide between the Popigay River [607] and Anabar [608] runs along the Syuryakh-Dyangy Range and Anabarskoye Plateau. The ecoregion encompasses the entire Putorana Plateau, including the lakes of the Khantayka River headwaters (the Yenisei system).

Topography

The extensive lowlands of the Bereg Pronchishcheva and Bereg Kharitona Lapteva coasts, which extend on either side of Cape Chelyuskin, grade into a plateau-like, mountainous area that gradually rises toward the Byrranga Mountains. The Byrranga Massif is equal in its area to the Caucasus and Alps; this is the northernmost mountain-glacier nucleus of Eurasia. The mountain ridges are terminated by steep, sometimes vertical, terraces with altitudes of 500 m. The river valleys cutting through limestone folds have the appearance of canyons with high rocky precipices and rapid riffle river channels.

The Putorana Mountains are a basalt plateau located in the northwestern part of the Central Siberian Plateau, south of the Taimyr Peninsula. It stretches from the Northern Polar Circle north to around 71° N, and from 88 °E to 101 °E. It occupies the major part of the rectangle formed by the Yenisei River on the west, Kotyi River (in its upper and middle flow) on the east, Kheta River (in its middle and lower flow) on the north, and Lower Tunguska on the south. The length of this mountain country is more than 500 km, and width is about 250 km. The average height of the mountains is 900-1200 m. The depth of the canyons is rather significant – up to 1500 m. The most typical amplitude of relative heights is 800-1000 m.

Mountains are cut by deep river valleys with relative elevations exceeding over 1000-1200 m. The thickness of the lava strata in the central part of the Putorana reaches 1500 m. In places with good outcroppings one can count over 40 lava layers. Tectonic splits comprise not only rivers, but also lakes that occupy widened riverbeds. They are numerous and large, stretching up to 110-133 km long and up to 185-420 m deep. Higher elevations have fractured relief that appears as deep somber canyons with steep slopes, depths of 100-120 m, bottom widths of 5-30 m or more, and lengths up to 2-6 km.

Freshwater habitats

The ecoregion includes water bodies of the Pyasina, Kheta, and Khatanga River drainages (apart from smaller rivers), and part of the Yenisei drainage. The numerous riffles and waterfalls regulating the exchange of faunas among different parts of river channels (and even separated hydrosystems) is important to the extensive hydro-network of the region.

The unique nature of many large lakes of the Putorana Plateau is accounted for by the fact that there are few areas in the Subarctic, Eurasia, and North America where water bodies that are unique in their hydrological characteristics are represented so densely in relatively confined areas. Lakes are one of the most outstanding landscape components of the Taimyr ecoregion, occupying about 10% of the area. Nowhere in the world can one see so many long (50-150 km) and deep (50-420 m) lakes as in the Putorana, especially in its western part. Although on the surrounding plains lakes occupy 30% - 60% of the area, they have much less water capacity.

Most of the largest lakes (about 50) have beds that were formed from expansion fissures. The vast majority of these are concentrated in the western and southwestern sectors of the Putorana Plateau. Some of the large lakes occur at approximately 500 m above sea level (Ayan, 470 m above sea level). However, most lakes lie at relatively low heights (Lama, 45 m above sea level). Systems of lake beds occur at different levels, and altitude differences approaching hundreds of meters (drainages of Kureika and Khantaika) are typical. Floors of lakes such as Lama, Glubokoye, Sobachye, Khantayskoye and others lie below the level of the world’s oceans. There are more than 42 lakes with an area in excess of 6 km, eight of which are among the largest water bodies of Siberia. Many of these are the deepest lakes not only in Siberia, but also in Eurasia.

There are more than 25,000 lakes on the Putorana Plateau. The longest (up to 150 km) and deepest (up to 420 m) of them appear in big basalt rifts. They are especially numerous in the western and southern parts of the Plateau. These lakes are the biggest in Siberia after lakes Baikal and Teletskoye. The depth of most of the lakes in the western part of the Putorana is 50-300 m lower than sea level. Altogether they are the second biggest surficial water reservoir in Russia after Lake Baikal.

Permafrost covers most of the plateau. The thickness of ice on lakes east of 93 °E reaches 1.8 - 2 m. Ice melting ends in the middle of July, and in the forest tundra subzone, in August. In early September small lakes are again covered with ice. The groundwater feed of rivers is trivial; rivers are recharged mostly from snow waters (55-70% of annual supply). The water table fluctuation reaches 4-5 m even in large lakes in the eastern Putorana Plateau. The permafrost layer in the lowlands attains a thickness of 650 m, although along tectonic fissures permafrost may be only 30-40 m thick, or lack underneath anabranches and large water bodies.

Terrestrial habitats

The Taimyr ecoregion comprises several terrestrial ecoregions, including Arctic desert in the north, Taimyr-Central Siberian tundra throughout most of the ecoregion, and East Siberian taiga along the southeastern edge.

Description of endemic fishes

The ecoregion contains no strict endemics. However, there are several near-endemic charrs. These include Esei lake char (S. tolmachoffi), Dryanin’s char (S. drjagini), and S. taimyricus. Salvelinus from Anadyr basin, commonly identified as boganidae, probably belongs to an undescribed distinct species, so Boganida char (S. boganidae) may be also near-endemic to the ecoregion.

Charrs of the genus Salvelinus are the most characteristic elements of the ichthyofauna in the Arctic region. Their distribution is circumpolar, i.e. they occur throughout the Eurasian coast, the North American coast, and in the continental zone. In lakes of the Putorana Plateau and in neighboring water bodies three species of Salvelinus have been described: Esei lake char, Boganida char, and Dryanin’s char. Moreover, one more near-endemic was found in Lake Taymyrskoye, S. taimyricus.

In some Norilo-Pyasinskiye lakes new forms of charrs were recorded: deepwater "pucheglazka," "black paliya," "mountain char," and small-sized "putoranchik". In the opinion of the researchers who described them they differ reliably from other known Taimyr endemics and deserve a definite taxonomic status. Up until recently the taxonomy of chars from water bodies of the Taimyr, unfortunately, has been insufficiently developed. The problem can be resolved through studies of the ecology and morphology of these chars, particularly in type localities, and obtaining more complete information of the composition of charr fauna from all of the lakes of the Taimyr Peninsula, especially the largest lakes.  

In the Khantai hydrosystem charrs are most widely spread in water bodies that form part of the Putorana lake-river province. These are mountain lakes (Kutaramakan, Khakancha, Khantaiskoye, etc.) and their tributaries with rapids, the majority of which are functioning only in the spring–autumn period. Charrs are especially diverse in Lake Khantaiskoye, particularly in its eastern part. They also occur downstream from Lake Khantaiskoye. Rarely do they occur in Khantaika, or even in the reservoir of the Ust-Khantaiskaya hydroelectric power station.

The studies carried out in Lake Khantaiskoye, the largest water body, reveal a relatively complex structure of the charr fauna. It consists of three common forms that differ by the external appearance of the head and gill apparatus. Apart from these, several “exotic” forms were found, which inhabit the system of Lake Khantaiskoye and adjoining water bodies, lakes Kutaramakan and Khakanchayu. Additional discussion of the status of these forms is needed.

Other noteworthy fishes

The sympatric occurrence of Arctic grayling (Thymallus arcticus) and Eastern Siberian grayling (T. pallasii) in Lake Khantayskoye and some rivers confirms the specific status of both graylings that were commonly considered subspecies. They are clearly different by details of shape and colorations of the dorsal fin (the main diagnostic character in graylings), and some morphometric characters. Often they inhabit different biotopes – T. arcticus is common in Lake Khantayskoye and its tributaries, whereas T. pallasii is mostly present in some tributaries upstream from waterfalls (Gogochenda, Kolyumbe, and other rivers), which prevent the distribution of T. arcticus.

Ecological phenomena

The wide variety of aquatic habitats supports a comparatively high (for Arctic conditions) level of diversity of fishes – species and infraspecific forms/morphs. In general, all of the species are adapted to critically low temperatures during most of the year. The most peculiar specializations are connected with food objects (available for short periods of time, and rather sparse and limited during most of the year) and depth of occurrence. In most lakes, there are two to three morphs of charrs – large-sized pelagic, deepwater, and dwarf ones.

Justification for delineation

The Taimyr Peninsula is the northernmost continental part of Eurasia and the largest area of virgin tundra (more than 400,000 km²) in the world. The northern extremity of Taimyr, Cape Chelyuskin (77° 43’ N), is the nearest projection of continental land to the North Pole. Situated even further north is the large Severnaya Zemlya Archipelago (its area is approximately 37,000 m²). Taimyr is called “a country of a thousand lakes,” the largest of which is Lake Taimyr. With an area of 4560 km² and length of 250 km, it is the largest freshwater basin of the Arctic. Taimyr is one of the World Wildlife Fund’s “Global 200,” an assemblage of roughly 200 ecoregions where more than 90% of the world’s biodiversity is concentrated.

Level of taxonomic exploration

Fair