Boundaries

This ecoregion includes the drainages of the Yuzhnyy (Southern) Bug and Dnieper rivers. The southwestern border runs along the Dniester-Yuzhnyy Bug divide—also known as the Podolskaya Vozvyshennost Upland. The region’s northern borders run along the Central & Western Europe ecoregion [404], the Southern-Baltic Lowlands ecoregion [408], and the Volga-Ural ecoregion [410]. This area appears naturally divided by the Valdaiskaya Vozvyshennost and Smolensko-Moskovskaya Vozvyshennost Uplands—between the Dnieper, Neva, Daugava and Volga drainages. 

To the northeast—in the Srednerusskaya Vosvyshennost Upland—the border divides the Dnieper River and Severskiy Donets (Don River tributary) drainages. The southeastern border moves along the divide between the Dnieper watershed and the rivers that drain (or once drained) into the Sea of Azov.  The southeastern border of the ecoregion encompasses the coast of the Black Sea where it lies adjacent to the Crimea Peninsula. 

Before canals were built on the Dnieper River, this area had no freshwater bodies. Today, the entire region is punctuated by canals of the Dnieper-North Crimea Canal system, and the water is pumped from the Dnieper River.

Topography

The Dnieper River’s catchment area is in the southwestern region of the Russian Plain, and occupies an area of 503 360 km². The Dnieper River begins in the Valdai Hills near the village Klevtsovo in the Sychev District (Smolensk Region). The river runs for 2285 km—with approximately 485 km in Russia and 720 km in Belarus. In Belarus, the catchment area’s terrain is flat and undulating, but hilly in the northwest. The Dnieper River cuts through spurs of the Orsha-Mogilev Plateau, where it has its greatest dip and highest flow velocity. Compared with the plain area to the south, the region’s rivers freeze much later and break up earlier.

Downstream from Orsha, the Dnieper River flows gradually through a valley of glacial deposits, into the Dnieper Plain. Artificial water routes connect the Dnieper River catchment area to the catchment regions of the Vistula (Dnieper-Bug canal), Neman (Oginsky canal) and Zapadnyaya Dvina (Berezina canal). The artificial canal connecting the Pina (a tributary of Pripyat) and Mukhavets (a tributary of Western Bug) rivers makes up the watershed of the Dnieper-Bug connection.

The Oginskaya watershed originates at Lake Vygonovskoye, which flows into the Yaselda (a Pripyat River tributary) and Shchara (a Neman River tributary) rivers. The Berezina watershed originates at Lake Manets, which drains into the Buzyanka River, Lake Domzheritskoye, and the Serguchevsky canal.  From there, the drainage waters flow into Berezina (the Dnieper River Catchment area), through Lake Plavno (a connecting canal), and into Lake Bereshcha before they join the Essa River. Lake Lepelskoye is the next stop before the watershed terminates in the Ulla River (a tributary of Zapadnaya Dvina).

The construction of the Dnieper Hydroelectric Power Plant in 1932 blocked anadromous and semi-anadromous fishes from the upper parts of the Dnieper River, and had large impacts on the ichthyofauna make-up of those areas. The Dnieper River feeds the region’s largest reservoirs: the Kievskoye (area: 922 km², volume: 3,73 km³), Kanevskoye (area: 675 km², volume: 2,62 km³), Kremenchugkoye (area: 2250 km², volume: 13,5 km³), Dneprodzerzhinskoye (area: 567 km², volume: 2,45 km³), Dniepersky (area: 410 km², volume: 3,3 km³) and Kakhovskoye (area: 2155 km², volume: 18,2 km³) reservoirs.

The Pripyat River is the Dnieper River’s largest left tributary, with a catchment area of 114300 km².  It originates about 25 km southeast from the meeting point between Belarus, Ukraine and Poland, which is approximately 10 km from the Western Bug River channel. The Pripyat River—862 km long in total—flows for approximately 230 km through the Ukraine and Belarus before joining the Dnieper River in Ukrainian territory. Belarus encompasses approximately 50% of the watershed.  The region is characterized by a sandy lowland valley, covered by peat deposits and both Quaternary and post-glacial deposits.  Roughly 60% of this catchment area is covered by swamps, while 30% is forested.  Lakes comprise only 0.15%, and are mostly situated near the upper reaches of Ukraine’s Pripyat River. In Belarus, the catchment’s largest lakes are Chervonnoye, Vygonovskoye Chernoye, Sporovskoye Bobrovichskoye, Beloye lakes. The Pripyat River’s floodplain contains a large number of small elongated lakes that were once closed parts of the old river channel (backwaters, branches and other natural river formations).

The Desna River is the largest left tributary of the Dnieper River. It is 1187 km long with a catchment area of 88400 km². The river begins in the swampy areas close to the town of Elnya (in the Smolensk Region), and flows into the Dnieper River near Kiev.  The Desna River’s high right bank is indented by ravines, while the left blank is low and swampy. The river has a wide swampy flood plain, with several oxbows and lakes. It frequently experiences spring flooding.

The Southern Bug River is one of the largest rivers in the Ukraine. It originates from the swamps in the Kamenets-Podolskaya region, and flows northwestwards through the town of Proskurov, southeastwards through Nikoklayev, and empties into the Black Sea’s Dnieper-Bug Liman.  The river is 857 km long, with a catchment area of 53,800 km². The Southern Bug River flows across low swampy banks before cutting deep into the crystal massif of the Volyno-Podolskoye Plateau, forming many stony rifts and rapids. The steep (slopes up to 90 m) valley that runs from Pervomaisk to Aleksandrovsk is home to famous rapids like Migeiskiye and Bogdanovskiye.  Downstream from Aleksandrovsk, the river flows into the Black Sea Plain.  Here, the valley and the river channel widen significantly. The Southern Bug drainage is pressed between the drainages of the Dnieper and Dniester rivers, and has a small annual discharge of barely 120 m ³  sec^-1.

Freshwater habitats

Most of the ecoregion’s rivers flow through “dismembered plain type” habitats.  These areas are characterized by wide valleys with gentle slopes and winding riverbeds. Woodland rivers (especially the Pripyat River’s right tributaries) have wide and superficial valleys, anywhere from 10 to 20 m. The river basins are typically quite boggy with areas of former riverbeds and floodplains. There are many branching rivers in the springtime.  Spring floods usually last for about 10 to 15 days on small rivers, 1 to 1.5 months for average-sized rivers, and 2 to 3 months for large rivers. Ice cover lasts anywhere from 2 to 3.5 months, but may remain for 4 months during severe winters.  The water remains ice free for about 240 days in the northeast portion of the ecoregion, and for about 270 to 280 days in the southwest. Water temperatures reach their maximum from July through August, varying from 20 ° C in the north to 24 ° C in the south.

Along the coasts of the Black Sea are a large number of limans (i.e. lakes or estuaries formed at river mouths), including the Dnieper – Bug liman, and others. Many of them are salt (mineral) lakes with thick deposits of silt. The limans have various connections with the sea; some of them are isolated from the sea by sand spits, whereas others retain a connection with the sea through narrow straights ("girlas"). Limans that are situated in estuaries of the Dnieper and Southern Bug rivers have an open outlet into the sea and a free water exchange with it. Limans of the Black Sea coast are believed to be a consequence of the postglacial or recent subsidence of the Russian continental platform. The Dnieper-South Bug estuary (liman) is the largest of all the Black Sea estuaries. It covers an area of 1006.3 km², and its volume is 4.24 km³. Its maximum length and width are 63 km and about 15 km, respectively. 

Historically, the deltaic and liman systems included numerous interconnected water bodies, both fresh and brackish, as well as wetland areas. The diversity of biotopes created a wide spectrum of ecological conditions and habitats that supported high biological productivity as well as high diversity of flora and fauna. Along the northern shore of the Black Sea, because the water has such a low salinity, freshwater fish enter saline areas and are able to migrate between the sea and rivers – behaviors not associated with these same species elsewhere in Europe. 

Terrestrial habitats

From north to south, the rivers of the ecoregion flow through forest, forest-steppe and steppe zones.

Description of endemic fishes

There are no strict endemic fishes. However, there are a handful of near-endemic species in this ecoregion.

Romanogobio belingi was once considered a subspecies of R. albipinnatus. This small, benthic, nocturnal gudgeon prefers moderately flowing lowland rivers with sandy bottoms. It is found in three ecoregions: the Northern Black Sea basin (the Dniester, South Bug and Dnieper river drainages), the southern Baltic basin (the Odra and Vistula rivers), and the southern North Sea basin (the Elbe and Rhine rivers).

Gobio sarmaticus was once considered conspecific with Gobio gobio, and inhabits the lower reaches of the Dnieper, South Bug and Dniester rivers. It is a typical benthic gudgeon that prefers low flowing, detritus-rich sandy habitats.

Benthophiloides brauneri is a rare species that inhabits coastal lakes, lower reaches of rivers, fresh and brackish waters of limans, as well as the northwestern region of the Black Sea. Some suggest it inhabits the Sea of Azov and Caspian Sea, but further study is required in both regions.

Other noteworthy fishes

Estuarine perch (Sander marinus) has a limited distribution range because of a very narrow range of salinity. It represents a remnant of the formerly common Parathetys in the Central and Southern Caspian Sea as well as in the Northwest Black Sea and Dnieper-Bug liman. It rarely entered the lower reaches of the Dnieper and South Bug rivers. There have been no reliable records of this fish for many years (our data; Yu. Movchan, pers. comm.).

Ecological phenomena

Besides the Volga River, the Dnieper and South Bug rivers are some of the most endangered river systems in the former USSR. This is a direct result of pollution and impoundments. All migratory species have disappeared, and Barbus barbus remains only because of some non-migratory riverine stocks.

Many fish species are adapted to entire river systems (the lower river reaches and mouths, the deltas or limans, and the adjacent brackish water area of the sea) to complete their life cycles. Semi-anadromous fishes such as roach (Rutilus rutilus heckeli), common bream (Abramis brama), vimba (Vimba vimba), ziege (Pelecus cultratus), and others forage in the Dnieper-Bug liman but migrate to the delta and lower reaches of Dnieper for spawning. Ripe individuals of Acipenser, Huso, and Alosa species enter the lower reaches of the Dnieper and Bug rivers, where they still have some spawning sites, and their offspring return to the delta and liman. The conditions in the ecoregion are favorable for such euryhaline species that inhabit both fresh and saline waters of up to 20-25‰ salinity.

Justification for delineation

This ecoregion encompassess the drainage basins of the Dnieper and South Bug rivers. This ecoregion is distinguished in part by a complete absence of Coregonus and Thymallus species. It lacks Dniester-Danubian endemic species like Zingel, Romanichthys, and Umbra, as well as a number of species under the genera Gobio, Romanogobio, and Sabanejewia.  However, it does contain Benthophilus nudus, which distinguishes it from the Don River system.

Level of taxonomic exploration

Good overall, but fair along the coast. Some nominal gobiid forms/subspecies from Benthophilus and Neogobius genera need revision as well as status and synonymies of migratory Alosa herrings.Good