engleski

Recent changes in scyphomedusan fauna in the Boka Kotorska Bay (southern Adri-atic)

There are various indications and claims that jellyfish have been increasing at a global scale in recent decades. Schyphomedusa species are a conspicuous, but they are generally little studied along the eastern Adriatic coast. In this study we present the results of five year monitoring (2013- 2017) on the Boka Kotorska Bay scyphozoans fauna. Data were obtained on the basis of reports organized through the actions of "Citizen Science", and by scientists of the Institute of Marine Biology, Kotor. The earliest commonly seen jelly-fish Aurelia spp. was very rare. On the other side, we noted considerable increasing abun- dance of Discomedusa lobata, Chrysaora hysoscella and Cotylorhiza tuberculata. The first bloom of D. lobata, estimated at 100 individuals per 10 m2, was in April 2014, with another in mid-May. The latter lasted two days, after which no individuals were observed. An extremely dense bloom at the end of March 2015 occurred in a shallow area influenced by spring water. These findings were the first insight into the mass occurrence of this species in the Mediterranean. The mass occurrence of C. hysoscella was found in spring time of 2014, 2015 and 2017. These blooms lasted between 3 and 10 days, but specimens were presence up to 30 days. Jellyfish C. tuberculata was previously rarely seen in the Boka Kotorska Bay. From the end of July to the mid of September 2017, it was constantly present and often in a large number of individuals. All these phenomena could relate with a sea-surface temperature global warming.

citizen science monitoring ; Discomedusa lobata ; Chrysaora hysoscella bloom ; global warming

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