The Adriatic Sea and the Tyrrhenian Sea
Cognetti, G.; Lardicci, C.; Abbiati, M.; Castelli, A. (2000). The Adriatic Sea and the Tyrrhenian Sea, in: Sheppard, C.R.C. (Ed.) Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. pp. 267-284
In: Sheppard, C.R.C. (Ed.) (2000). Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. Pergamon: Amsterdam. ISBN 0-08-043207-7. XXI, 934 pp., meer
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Documenttype: Revisie
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| Auteurs | | Top |
- Cognetti, G.
- Lardicci, C., meer
- Abbiati, M., meer
- Castelli, A., meer
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| Abstract |
The Adriatic Sea differs sharply from the Tyrrhenian Sea and the rest of the Mediterranean in its hydrographic and hydrobiological characteristics. Three different areas can be distinguished: the Northern, the Central and the Southern Adriatic. The first shows the most accentuated peculiarities: maximum depth does not exceed 40 meters, temperature may fluctuate between 5°C and 28°C during the year, salinity is highly variable, and tides may rise higher than 1 m. Organic matter input from rivers, and the resulting nutrient enrichment, leads to elevated primary productivity , particularly in the Northern and the Central Adriatic. Both the circulation and distribution of water masses in the Adriatic Sea are strongly influenced not only by the morphology of the three basins but also by the fresh water inflow of continental origin. In the Tyrrhenian Sea the continental shelf extends only for a relatively short distance. The depth exceeds 2000 m throughout virtually the whole of the basin, with a maximum depth of 3840 m. Input from the continental waters is minimal so salinity remains constant at roughly 38 PSU. In winter the Tyrrhenian Sea maintains a constant temperature of about 13°C, while in summer the temperature is around 23-24°C. The mean value of primary productivity is much lower than in the Adriatic. The surface Atlantic current feeds a cyclonic gyre with a southern branch entering between Sardinia and Sicily and moving in a northeasterly direction, and the other towards the southwest. Levantine intermediate waters penetrate mainly through the strait of Sicily at a depth ranging between 300 and 400 m. A clear distinction between coastal and off-shore habitats is found only in the Southern Adriatic where the bottom drops to considerable depths. Particularly significant is the beach-rocks habitat enclosed within the surrounding soft bottom. Bathial fauna are found only in the Southern Adriatic. The extensive coastal lagoons are of considerable ecological and biogeographic interest. Several endemisms are known, some of sarmatic origin. Only the Central and Southern Adriatic are characterised off-shore by an oceanic planktonic community .The Northern Adriatic is characterised by neritic plankton throughout its extension. Production of nanoplankton is dominant. In the Tyrrhenian Sea the hard bottom communities are amongst the most important of the whole Mediterranean. Of particular interest are the 'trottoir' and the coralligenous formations typical of the Tyrrhenian Sea which can develop on rocky and sandy bottoms at depths ranging between 20 and 1230 m. Zooplankton shows some characteristics that distinguish it from other areas of the Western Mediterranean. Abyssal fauna is present in the centre of the basin although it is considerably poorer than that of the Atlantic. Along the coast of both seas there are important ports and numerous large urban centres whose population is substantially increased during the tourist season. The numerous industrial complexes co-exist with intense agriculture and animal-rearing activities. Maritime traffic is intense. The most important fishing ports are in the Central and Southern Adriatic and aquaculture is highly developed. In the Adriatic natural gas reserves and oil fields lie along the Italian coast: there are 70 off-shore platforms, and oil or gas flows to the mainland through pipelines. Water quality is impaired by a number of factors, particularly the excessive quantity of nitrogen and phosphorus. On the Tyrrhenian sea floor, several areas of interest for mineral extraction have been identified. The presence of cinnabar mines in Tuscany has increased the levels of mercury in the water and sediment in the Northern Tyrrhenian. Other metals are also present in considerable concentration in the waters of the Southern Tyrrhenian due to underwater volcanic activity. Both the Adriatic and Tyrrhenian have been included within the framework of protective measures set up on the basis of international conventions. Considerable progress has been made in designing waste purification technology and measures designed to establish protected marine areas are already in place. Interdisciplinary research developed in the universities and in various research centres has long been a driving force and has made a crucial contribution to knowledge of oceanography and marine biology. Proposals based on data concerning the current ecological situation have also been put forward, aimed at water clean-up and improving fishery production. |
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