lagoon

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Natural lagoon of Karavasta in Albania, protected as a national park

A lagoon is a relatively shallow body of water that is largely or completely separated from the sea by sand deposits ( spit ) or coral reefs - such as in an atoll .

In Latin America , shallow lakes inland (often temporary river lakes in floodplains) are also referred to as laguna .

Use of language

Asan Foun , a freshwater lagoon on the south coast of East Timor

The word lagoon is derived from the Italian laguna ("water surface lying in a swamp"; swamp, beach lake, Haffsee) from the Latin lacuna (pond, pool). On the Western Pomerania and Polish Baltic coasts , lagoon-like waters can be found in bays called Haff and Bodden , and in Schleswig-Holstein in bays called Noore . On the Black Sea , lagoon-like coastal waters in the mouth of the rivers are called Limane . Often lagoons have parts of their names such as lake or bay .

The demarcation to small inland seas is fluid, with relatively small (mostly a few hundred square kilometers area) and particularly shallow (rarely more than 10 meters) waters being considered lagoons.

Emergence

In moderate latitudes and clastically dominated coasts, lagoons are created from “normal” bays: these bays are separated from the open sea by shifting the beach , which leads to the formation or extension of sand hooks and spits . If the separation is complete, the lagoon becomes a beach lake , which slowly sweeps up in a humid climate . As long as there is a connection to the open sea, the lagoon contains brackish water . In an arid climate, on the other hand, lagoons and beach lakes tend to be over-salted.

The lagoons on the carbonate- dominated coasts of tropical latitudes emerge completely differently . There the lagoon is bordered by the reef crown of a coral reef against the sea, that is, the material from which the barrier is made is not washed ashore by currents, but is produced on site by the reef-building organisms (not just corals). There, too, the climate determines whether the lagoon is brackish or over-salted. Atolls represent a special case of this lagoon formation. Here , a small oceanic volcanic island sinks or is eroded while its fringing reef grows fast enough to keep up with the sinking. In the end, all that remains is the ring-like fringing reef near the sea surface and where the volcanic island once protruded from the sea is the lagoon. If an atoll is raised , the lagoon falls largely or completely dry. The remaining depression and / or a lake in it then retains the designation "lagoon".

Human influences

Since lagoons are usually poorly accessible, they have in many cases been preserved as ecosystems that are little influenced by humans . These wetlands serve as important retreats for water birds , fish , smaller animals and plants. The ecologically most important lagoons are protected internationally by the Ramsar Convention .

An example of a - at least partially - developed and used lagoon is the lagoon city of Venice near the mouth of the Po in Italy . The reason for founding cities in lagoons is usually the very safe location. Many lagoons are also very rich in fish, which was of great economic importance for the residents of the area, especially in the past.

Examples of lagoons

Germany

The Neuwarper See (right) near the fishing village of Altwarp is a lagoon on the German-Polish border in the south of the Szczecin Lagoon .

Worldwide

  • Lake Maracaibo (13,512 km²) is known as an inland sea, but has a connection to the ocean and is therefore considered a lagoon.
  • One of the world's largest lagoons is the Lagoa dos Patos (10,145 km²) in Brazil , on the banks of which is the city of Porto Alegre .
  • The approximately 460 km² lagoon of Lagos is located east of the metropolis of the same name and is perhaps the best example of a lagoon landscape that is ecologically endangered by anthropogenic influences. The water, which is heavily polluted with pathogenic bacteria, only reaches a depth of two meters and is one of the largest lagoons on the African continent.
  • The Mar Menor is a 170 km² saltwater lagoon in the Spanish region of Murcia and the largest salty inland water in Europe.
  • The lagoon of Venice with the lagoon city of the same name is very well known . The expansion reaches around 550 km².
  • There are also several large lagoons on the Adriatic in Albania, such as the Vain-Kune-Patos lagoons, the Karavasta lagoon , the Narta lagoon and the Butrintsee , which are important nature reserves and Ramsar reserves .
  • Another important lagoon in the Mediterranean is the Messolongi lagoon (33.5 km²) in the Messolongi Delta ( Greece ), the delta of the Acheloos River . At the northern end of this lagoon is the small town of Aitoliko on an island, followed by the lagoon of Aitoliko.
  • Ahunui as an example of a lagoon completely enclosed by atoll islands.
  • The bay and lagoon of Walvis Bay is one of the largest bird sanctuaries in Africa; as well as the nearby lagoon of Sandwich Bay .
  • The mouth of the Megalopotamos dammed to the 15,000 m² small lake of Preveli on the beach of Preveli .

Web links

Commons : lagoons  - collection of images, videos and audio files
Wiktionary: Lagune  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Keyword Lagune ( memento from January 10, 2016 in the Internet Archive ) at GeoDataZone
  2. ^ Johann Jakob Egli : Nomina geographica. Language and factual explanation of 42,000 geographical names of all regions of the world. Friedrich Brandstetter, 2nd ed. Leipzig 1893, p. 521
  3. ↑ Formation of a lagoon and definition
  4. ↑ Definition, description, distribution ( Memento from June 22, 2013 in the Internet Archive )
  5. ^ Gösta Hoffmann: The island of Usedom - late Pleistocene and Holocene landscape development. In: Reinhard Lampe, Sebastian Lorenz (Ed.): Ice Age Landscapes in Mecklenburg-Western Pomerania. Geozon Science Media, Greifswald 2010, ISBN 978-3-941971-05-9 , p. 107 ( online ).
  6. ↑ Lagona dos Patos
  7. ↑ Laguna Mar Menor
  8. ↑ Venice Lagoon
  9. ↑ Karavasta Lagoon (PDF; 58 kB)
  10. ↑ Albania. In: Ramsar. Retrieved July 25, 2016 .