Biologists from Dubrovnik conducted a 25-year study of jellyfish in the southern Adriatic, and the results were deemed beneficial in comparison to the Mediterranean Sea and in accordance with the aims of the Framework Directive to attain "excellent ecological status" of the sea.

Biologists from the University of Dubrovnik, Ivana Violi, Davor Lui, Barbara Gangai Zovko, Ivona Onofri, and Marijana Hure, in collaboration with Branka Pestori from the University of Montenegro and Natalija Bojani from the Institute of Oceanography and Fisheries in Split, conducted a study from 1996 to 2020 on the occurrence and abundance of jellyfish in the Dubrovnik-Neretva

The jellyfish with the greatest density in the southern Adriatic.

They discovered 15 different species of jellyfish, with three of them being the most numerous. Pelagia noctiluca, a bell-shaped ski jellyfish, is the most abundant jellyfish in the southern Adriatic, accounting for one-third of all observations of this species. It is inconvenient for swimmers and has the potential to cause health problems. The increasing acidity of the ocean has a significant role in its spread. It is believed that this jellyfish contributes to "bloom of the sea," and particularly enormous quantities have been observed between 2003 and 2007.
The ribbed Venus belt (Cestus veneris) is the second most frequently observed object, accounting for almost a fifth of all observations. It is extremely delicate, and it can grow to be up to one meter long.

The third species is the skiff jellyfish Cotylorhiza tuberculata, which is found in 17 percent of the world's waters and is the most abundant among the masses. Moreover, he points out that the amount of its flowering in the southern Adriatic was nowhere like the extent of flowering in the northern Adriatic.

Sides of jellyfish

The arrival of three species of jellyfish that are not native to European waters is highlighted in the text of the article. It is a freshwater hydromedusa, Craspedacusta sowerbii, which was discovered in Lake Kuti, at the mouth of the Neretva River, in an isolated mass occurrence for the first time.

Foreign species such as Aurelia cf. solida, which is much more common in the northern Adriatic, and Mnemiopsis leidyi, one of the most invasive marine species, have also been detected in the port of Ploe on multiple occasions.

According to our findings, the introduction of M. leidyi into this area was induced by the discharge of ballast water from ships carrying cargo from the northern Adriatic. Indeed, since the summer of 2016, this invasive species has been consistently present in the northern Adriatic during the warm season, frequently in unusually large numbers, and the scientists note that the species' effects on biogeochemical cycles and the food web are now becoming apparent.

Several foreign jellyfish species have been detected in the Mediterranean, with up to six of these species found in the Adriatic Sea, according to recent research. Several of them have a significant potential to live in the Adriatic Sea, according to the research.

So far, the situation is favorable, but there are threats.

For instance, the authors highlight that the permanent settlement of blue crab (Callinectes sapidus) in the Neretva delta, which is the result of ballast water discharges, is an example of a negative impact on the ecological system and biodiversity.

Conclusion: According to the authors' findings, "the eastern coast of the southern Adriatic is inhabited by a reasonably stable jellyfish fauna, whose composition and quantity have not changed dramatically in recent decades," i.e., the jellyfish population has remained relatively steady over time. "Good ecological status" must be achieved.

More massive blooms of gelatinous, carnivorous plankton species, commonly referred to as "jellyfish" species, can occur in the ocean and have a variety of negative environmental consequences, including harm to human health and economic activities such as fishing and aquaculture, according to the text. Overfishing, habitat destruction, and global climate change are all encouraged.