engleski

The water and biology on a small Karstic island: the Island of Brac (Croatia) as one example

The objective of this paper was to stress the significance of a holistic interdisciplinary approach to analyses of a small karst island valuable and vulnerable ecosystem. To reach that aim, this paper presents ecohydrological data and standard methods of biological surveying in subterranean habitats. The Island of Brač, with a total area of 394.57 km2, is the third largest Croatian island in the Adriatic Sea. The island stretches east–west direction between 43°16′ and 43°23′ N and 16°25′ and 16°54′ E. The penetration of surface water through calcareous substrate into the underground and the sea water from the Adriatic side has created a system of caves, and this study investigated 225 pits and caves of such a nature. An overview of karst ecohydrological characteristics on the island of Brač through its geology, climatology, geography, speleology and biology is given. A decrease in rainfall and increasing air temperature were observed. If these processes continue, this vulnerable island ecosystem can be endangered. This paper also includes an analysis of the physicochemical parameters and faunal composition of six groundwater habitats: the spring “Martinica”, the mine “Minjera”, the pit “Jama u Kotliću”, the pit “Jama na Bijaki”, the pit “Jama u Podstražišću” and the well “Studenac”. Based on salinity, the groundwaters are limnic and anchihaline. The subterranean macroinvertebrate fauna consists of Gastropods and Crustaceans. Two records confirm the new gastropod genus and species Semisalsa n.sp.? and Hydrobiidae n.g. et n.sp. Preliminary anatomical data on Balkanostenasellus specimens show significant differences between the described Balkanostenasellus species. Other crustacean representatives are Niphargus hebereri and Titanethes sp. All faunistic results are the subject of further taxonomic surveys and provide a significant contribution to increasing knowledge about subterranean fauna in Croatia, as well as their protection.

Karst ; Groundwater ; Subterranean fauna ; Island of Brač ; Croatia

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