engleski

Circalittoral biocoenoses and coralligenous formations in the Northern Adriatic Sea

The Norther Adriatic circalittoral is mostly characterized by monotonous seabeds, whose dominant biocoenosis ia the muddy detritic. They are interrupted by precoralligenous detritic bottoms and biogenic formations, such as the rocky outcrops called Tegnue and the reefs of Cladocora caespitosa. These habitats are severely endangered, due to intensive fishery and other environmental disturbances. To manage their protection, the knowledge of their extent and the classification of the habitat type, in agreement with the most recent Directives and International Protocols, is essential. No general consensus exsists on the criteria to categorize the coralligenous and a number of definitions is proposed based on noth-western Mediterranean evidences. The available list of species, as well as the main engineering species, are known from these areas, while they cannot be considered to be constant in the rest of the Mediterranean. This paper represents an up-to-date contribution to the knowledge of compoosition and distribution of circallitoral biocoenoses and to the understanding of coralligenous formations in the Northern Adriatic. The study is based on literature data and on most recent researches carried out on rocky outcrops off the Gulf of Venice and Trieste, and on the circallitoral detritic bottom off the Slovenian coast. Rocky outcrops display a wide range of morphologies that, together with environmental factors and human pressures, influence the habitat complexity and thus biodiversity. They are characterized by a rich biodiversity and different assemblages, not all referable to the coralligenous that distinguish the less disturbed off-shore areas. The contribution of different bioconstructors and a draft list of the main coralligenous taxa recognized are provided. The coralligenous biocoenoses of the Northern Adriatic seem to differ from the Mediterranean ones, mainly for a higher number os suspension feeders and for a lower morpho-functional complexity of the communities. Finally, long-term changes in assemblage composition and species abundances were highlighted.

benthic biocoenoses; formation; circalittoral; coralligen; North Adriatic

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