Black Sea :: Hydrology -- Britannica Online Encyclopedia
A marked increase in salinity, up to 21 parts per thousand, occurs at depths of roughly 160 to 500 feet (50 to 150 metres), below which the salinity increase is much more gradual. Although Austria is landlocked, its shipyards build vessels for Austria and for other countries. Encyclopædia Britannica Online.06 May. Flows in the Bosporus are complex, with surface Black Sea water going out and deep saltier water coming in from the Sea of Marmara. In summer the surface layer is warmed to between 73 and 79 °F (23 and 26 °C). In winter, water temperature ranges from 31 °F (− 0.5 °C) in the northwest to about 48 to 50 °F (9 to 10 °C) in the southeast. It is among the most visited reserves in Ukraine, the attractions including many species of waterfowl, and is the only breeding ground in Ukraine of the gull Larus melanocephalus. It was across its waters that, according to legend,... Known as limans, these bodies of water form at the mouths of rivers or ephemeral streams and are blocked off by... Larger saline lakes occur along the coast. One of the largest is Lake Svityaz, 11 square miles in area, in the northwest. Salinity increases to 38 parts per thousand at the Bosporus, where waters from the Sea of Marmara intrude. Small saltwater lakes occur in the Black Sea Lowland and in the Crimea. Surface winds are an important complicating factor, especially in the shallow sill, or threshold, between the two basins. The annual water level, therefore, varies slightly according to factors influencing any one or more of these components. The Black Sea coastline is otherwise fairly regular. The chemical composition of Black Sea water is almost the same as that of the oceans.A most important feature of the Black Sea is that oxygen is dissolved (and a rich sea life is made possible) only in the upper water levels. The current is relatively slow on the surface in the open sea, but near the shore it reaches 16 to 20 inches (40 to 50 cm) per second; its speed is only 1 inch (2.5 cm) or so per second in the depths. The Danube Water Meadows (Plavni) reserve (36,600 acres)... The grassy steppe vegetation has been preserved only in the nature reserves and preserves and in old ravines...physiography of Ukraine Ukraine...lakes, all of them small and most of them scattered over the river floodplains. The lower Dnieper basin lies within the Black Sea Lowland, in the black-soil steppe area, which has now been completely plowed up. The maximum east-west extent of the sea is about 730 miles (1,175 km), and the shortest distance between the tip of the Crimea and the Cape Kerempe to the south is about 160 miles (260 km). The principal tributaries of the middle Dnieper are the Ros, Sula, Pesl, Vorskla, and Samara. The renowned Crimean Peninsula thrusts into the Black Sea from the north, and just to its east the narrow Kerch Strait links the sea to the smaller Sea of Azov. The sea’s deepest parts (below about 1,300 feet [400 metres]) are distinguished by highly stable temperatures between 47 and 48 °F (8.5 and 9 °C) and salinities of 28 to 30 parts per thousand. The surface area, excluding the Sea of Marmara but including the Sea of Azov, is about 178,000 square miles (461,000 square km); the Black Sea proper occupies about 163,000 square miles (422,000 square km). The winter cooling forms an upper mixed layer extending to depths of about 160 to 330 feet (50 to 100 metres), with temperatures at the lower boundary of about 44 to 46 °F (6.5 to 8 °C). The young of the black sea bass (Centropristis striata) are mostly females with normal egg-laying functions; after five years, however, some of these females transform into functional males. This situation also holds for flows to and from the Sea of Azov through the Kerch Strait.
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