Terrestrial Environment of Lithuania

Geographic position.
Lithuania is situated in the geographical centre of the European continent; it is bordered by Latvia to the north, Belarus on the east and south, and Poland and Russia (Kaliningrad Oblast) on the southwest. The Baltic Sea borders the west coast.

Climate.
Climate in Lithuania is temperate, dominated by the country's nearness to the Baltic Sea. In the western coastal area, summers are cooler and winters are milder than in the eastern, more continental part of the republic. Average annual precipitation ranges from less than 600 millimeters per year in central Lithuania to more than 850 millimeters per year in the west. The long-term average temperature in summer is 17 °C, in winter 4 °C.

Main types of habitats.
Lithuania consists of a low-lying plain broken by low hills in the west and south. About 30,6 % of the territory is covered by mixed large-leaved and coniferous forests. Marshes and swamps are common, especially in the north and west, although half of the original wetlands have been drained.

Aquatic Environment of Lithuania                                                             Top

The Lithuanian zone of the Baltic Sea is situated in the south-eastern part of the Baltic Proper (Figure 1). The shoreline, from the Russian (Kaliningrad) border on the Curonian Spit to the Latvian border on the mainland, is 92 km long. The aquatic environment comprises the Baltic Sea Proper coast, the Curonian Lagoon and the inland waters.

Figure 1. Lithuanian coastal waters and major rivers.

Baltic Sea coast.
The offshore waters show the typical stratification pattern for the Baltic Proper with the upper layer (mean salinity 7-8 PSU) separated by a permanent halocline at 70-80 m depth from the more saline subhalocline water layer which is oxygen deficient. In the coastal area major hydrological features are determined by the interaction between the south-eastern Baltic offshore waters and the runoff of the mostly freshwater Curonian Lagoon. Often the frontal zone between the sea and lagoon water is very narrow (20-40 m), and because of obvious differences in water colour and transparency, it may be easily visible (Olenin & Klovaite 1998). The average temperature of the coastal waters has an annual range of 22 °C, showing a typical boreal seasonal pattern. In July-August the summer thermocline is formed at the depth of 20-30 m, so almost all the coastal zone is influenced by the warm water above the thermocline. In winter, ice is a normal phenomenon along the shoreline; its width varies from 20-30 m to several hundred metres, with a thickness from 10-15 to 40-50 cm, depending on the severity of the winter. The permanent influence of winds, waves and water currents produces a hydrodynamically very active environment resulting in no oxygen deficiency and no oxygen based gradients in the distribution of bottom biota in the coastal area in contrast to the deeper offshore areas.

Curonian Lagoon.
This is the largest coastal lagoon in the Baltic Sea. It is an enclosed shallow (mean depth 3.7 m) lagoon, connected to the Baltic Sea by the narrow (width 400-600 m) Klaipėda Straight. The southern and central parts of the lagoon are freshwater due to discharge from Nemunas (98% of total) and other rivers, while the northern part is oligohaline with irregular salinity fluctuations from 0 to 8 PSU. Water temperature shows a typical boreal pattern with highest values (23-25 °C) from July to August. From December to February the lagoon is usually covered by ice. The Lagoon is a highly eutrophied water body with blue-green algae blooms being a regular annual phenomenon from the end of June until the beginning of November. The main water current in the Curonian Lagoon is the outflow of the Nemunas (Neman) River, which empties into the Baltic Sea near the port of Klaipėda.

Inland waters.
The main river of Lithuania is Nemunas, which rises in Belarus. Other important rivers are Neris and Sesupe (tributaries of Nemunas) as well as Venta and Musa (Lielupe) emptying into the Gulf of Riga in Latvia. There are 2830 lakes larger than 0.5 ha in Lithuania, their total area is 880 km². The major lakes are Druksiai, Dysnai and Dusia.

Invasion Corridors                                                                                             Top

Klaipėda is the only commercial sea port in Lithuania (Figure 1). It is the third largest port in the Baltic States and the most northern ice-free Baltic seaport. Harbour waters do not freeze even at air temperature -25°C. Every year, about 7,000 ships call the port. They release from 2 to 4 M tonnes of ballast water annually (Olenin et al 1999). However, yet no one primarily ballast water related introduction was detected in Klaipėda port. All invasive species of “ballast water origin” appeared in the Lithuanian coastal waters due to semi-natural secondary spread from other, previously inoculated parts of the Baltic Sea.
The Lithuanian inland waters are connected with the drainage basin of the Black Sea by canals (Figure 2). The first canal, which linked the rivers belonging to the Baltic Sea and Black Sea watersheds, was the Oginskij Canal, named for then Voivode of Vilnius, who built the canal in 1765-1768 (Kolupaila 1953). The canal itself is 54 km long, connecting the lake Vygonovskoje with Jaselda, an affluent of the river Pripet, which in turn is the major tributary of the river Dnepr. On another side, the river Shchara springing from that small (max length 7 km) lake flows into the river Nemunas (Neman). Primarily the canal was built for the rafting of timber from the Belarusian Polesjye down to the Baltic Sea ports, Klaipėda (former Memel) through the Curonian Lagoon, and Gdansk (Danzig) through East Prussian rivers (Deima, Pregel), small canals and the Vistula lagoon. The Oginskij canal was destroyed during the World War I and II (in 1916 and 1944), but then reconstructed (Kolupaila 1953).

Figure 2. Channels (with dates of construction), connecting Dniepr river with the south-eastern Baltic coastal lagoons (Vistula and Curonian).

It is most likely, that the introduction of the zebra mussel Dreissena polymorpha into the Vistula and Curonian coastal lagoons in early 1800s was due to transportation of molluscs attached to timber rafts. It is interesting that the next “destination point” of that species in Western Europe was London (1824) and Amsterdam (1826), at that time the recipient ports for the Baltic timber trade (Olenin et al 1999b). Only after that, the species started to spread in inland waters of western and central Europe.
There are several other invertebrate species which most likely invaded the Baltic Sea coastal regions, during the 19th century and early 1900s, through the above invasion corridors. The hydrozoan Cordylophora caspia dwells on hard substrates; the corophiid amphipod Chelicorophium (Corophium) curvispinum also attaches its tubes to hard surfaces (including mussel shells) and the snail Litoglyphus naticoides usually inhabits the zebra mussel aggregates in the Curonian lagoon (Olenin 2002; Jazdzewski & Konopacka 2002). All these species could use rafts and boats for their travel along canals and rivers.

References                                                                                                            Top

Jazdzewski & Konopacka 2002. Jazdzewski K. & Konopacka A., 2002. Invasive Ponto-Caspian Species in Waters of the Vistula and Oder Basins and the Southern Baltic Sea In: Invasive aquatic species of Europe - distribution, impact and management. Leppäkoski E, Gollasch S & Olenin S (eds). Dordrecht, Boston, London. Kluwer Academic Publishers: 384-398
Kolupaila 1953. Kolupaila S., 1953. The Oginskij Canal. In: The Lithuanian Encyclopaedia, v. 21. Chicago, USA: p. 36 (in Lithuanian).
Olenin 2002. Olenin S (2002) Black Sea - Baltic Sea invasion corridors. In: Alien marine organisms introduced by ships in the Mediterranean and Black Seas. CIESM Workshops Monograph. F Briand (ed.) Comission Internationale pour l'Exploration Scientifique de la mer Mediterranee., Monaco: 29-33
Olenin & Klovaite 1998. Olenin S & Klovaite K (1998). Introduction to the marine and coastal environment of Lithuania. In: Red list of Marine and Coastal Biotopes and Biotope Complexes of the Baltic Sea. H. v. Nordheim and D. Boedeker (ed-s). HELCOM. Baltic Sea Environment Proceedings, No.75: 39-43
Olenin et al. 1999. Olenin S, Olenina I, Daunys D & Gasiunaite Z (1999). The harbour profile of Klaipėda, Lithuania. In: S. Gollasch and E. Leppäkoski (eds). Initial Risk Assessment of Alien Species in Nordic Coastal Waters. Nordic Council of Ministers. Nord, 8: 185-202
Olenin et al 1999b. Olenin S, Orlova M & Minchin D (1999b) Dreissena polymorpha (Pallas, 1771). In: Gollasch S, Minchin D, Rosenthal H & Voigt M (eds) Exotics Across the Ocean, pp 37-42. Logos Verlag, Berlin

Compiled by A.Zaiko

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