Mass occurrence of the ctenophore Bolinopsis vitrea (L. Agassiz, 1860) in the nearshore southern Adriatic Sea (Kotor Bay, Montenegro)

The ctenophore Bolinopsis vitrea has been rarely observed in the Mediterranean Sea. A bloom of B. vitrea is here reported for the first time in the southern Adriatic Sea in the spring and summer of 2009, together with its effect on the plankton of Kotor Bay. Ctenophores were found below 5 m depth only. Results of the investigation indicate that mass occurrence of B. vitrea could have a great impact on the Kotor Bay ecosystem. Their predation on copepods would reduce grazing pressure on phytoplankton, favouring an uncommon bloom of the latter. It is evident that B. vitrea are capable of altering rapidly the composition and biomass of coastal plankton communities when present in large masses. This first evidence of such events for this species may indicate changes in the functioning of marine ecosystems of the southern Adriatic.