engleski

Does a recent change in the northern Adriatic hydromedusan fauna indicate the possibility of species repopulating?

During the last 50 years ecological changes were already noted in the northern Adriatic, and many species disappeared from this zone. Following concern about substantial changes in the northern Adriatic, in this study we present the comparative results of the composition and abundance of hydromedusan fauna of northern Adriatic, pointing to the possibility of species repopulating recent years. Presented data are results of investigations during three study periods: the first from 1999-2002, second from 2003-2007 and the third from 2009-2011. Our results clearly showed that the number of species and their abundance increase from the first to the third investigated period. We assume that some species were introduced by input currents in the northern Adriatic, which is confirmed by the increasing density of trachymedusa, but abundances of some species were several times higher than in previous records. Although the abundance of hydrozoan species vary during their life cycles, our high mean and maximum values of this metagenetic specimens could indicate the possibility of establishing stable populations in the area. These changes are consistent with the recent changes in the plankton composition and abundance, probably caused by a climatic forcing and recognized oligotrophication of the entire northern Adriatic.

Adriatic Sea; biodiversity; oligotrophication

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