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Abstract: The Eastern Adriatic Sea is biogeographically complex, yet knowledge of its hydromedusae is fragmented across two centuries of uneven sampling and shifting taxonomy. This review integrates historical faunistic records (pre-1950), mid-century programmes (1950–2000), modern quantitative time series (post-2000), and citizen science observations to compile an updated checklist of 98 non-siphonophoran hydrozoan taxa. Records are synthesised across eight sub-regions, although the most continuous research has focused on the Northern Adriatic and the open South Adriatic. The clearest long-term signal is in the Northern Adriatic, where diversity collapsed by >60% from the 1960s to the 1980s, largely through the loss of meroplanktonic taxa with benthic polyp stages under eutrophication-driven hypoxia. Since 2000, oligotrophication coincides with a partial recovery, marked by the re-emergence of meroplankton and episodic intrusions of oceanic holoplankton (including Trachymedusae) linked to circulation regimes (BiOS). For the open South Adriatic, bathymetric distributions and diel vertical migration patterns are synthesised to characterise a persistent offshore core. Taxonomic updates and information on non-indigenous and bloom-forming taxa are provided. Methodological biases and gaps, especially polyp-stage ecology and spatial sampling voids, are highlighted, and routine DNA barcoding is recommended. The checklist provides a baseline for tracking change in a shifting ecosystem.
Keywords: gelatinous zooplankton, ecological collapse and recovery, citizen science, meroplankton, taxonomic checklist
Published in DiRROS: 02.03.2026; Views: 250; Downloads: 160
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Abstract: Although geographically well apart, there are interesting similarities between the ecosystems of the Sea of Marmara and the Adriatic Sea. In this study, following an evaluation of the ecological problems as well as oceanography, productivity, plankton biomass of these seas, macro-jellyfish ecology of the two ecosystems were discussed comparatively. The Sea of Marmara and the Adriatic Sea are among the areas where increases in jellyfish and mucilage events have been observed in recent decades. Environmental problems such as global warming, oxygen depletion, eutrophication, overfishing, intense maritime traffic, and habitat destruction are causing opportunistic and alien species to increase in both abundance and number of species. As biodiversity declines due to habitat destruction, so does the ecosystem’s means and ability to combat the invasion of alien species in both ecosystems. Accordingly, disruption of lower food chains can put pressure on the entire ecosystem and affect socio-ecological prospects. The number of species of Scyphozoa and Ctenophora was found to be higher in the Adraitic Sea compared to the Sea of Marmara. Mass occurrences with a clear seasonal pattern and related to the geographical location were observed for Aurelia aurita, Rhizostoma pulmo, Chrysaora hysoscella and non-native Mnemiopsis leidyi in the Marmara Sea. However, although A. aurita and R. pulmo show widespread blooms according to the seasons and regions in the Adriatic Sea, C. hysoscella and M. leidyi produced blooms limited to a few areas. Negative and positive interactions of macrojelyfishes with human were also considered. Semi-enclosed seas such as the Sea of Marmara and the Adriatic Sea are representative of many temperate coastal waters where climate change and anthropogenic stressors are increasing, and the ecosystem has changed from a fish-dominated to a jellyfish-dominated ecosystem.
Keywords: jellyfish, eutrophication, diversity, introduce, fisheries
Published in DiRROS: 07.05.2025; Views: 963; Downloads: 687
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Abstract: Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom - forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish - enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to ‘jellyfish - associated’ and ‘free - living’ bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in bacterial population dynamics and nutrient pathways following jellyfish blooms which have important implications for ecology of coastal waters.
Keywords: sea, medusae, research programmes, DGGE, Pelagia noctiluca, gel electrophoresis, oligotrophic waters, Adriatic Sea, jellyfish, gelatinous zooplankton, bacteria, flavobacteria
Published in DiRROS: 26.03.2025; Views: 2579; Downloads: 855
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Abstract: The interdependence between the economy and the environment is becoming a fact of increasing importance. Productive coastal areas have been recognised as one of the most valuable ecosystems from an ecological and socio-economic point of view. In this paper we focus on the massive presence of jellyfish in the northern Adriatic and their effect on the Slovenian economy. Our results indicate that high jellyfish abundance in 2004 resulted in a reduction of fish catch, value added, gross income, and employment in the fishing industry. Moreover, the government and the EU have acknowledged the impact of jellyfish on the fishing industry by allocating financial help to the fishermen involved. We attempted to assess other factors influencing the fishing industry but none were statistically significant. The input-output analysis has not revealed a significant impact on the entire Slovenian economy presumably due to the small contribution of the fishing industry to Slovenian GDP. Our work is a first attempt to relate ecological changes such as jellyfish outbreaks in the northern Adriatic to the wider economy and we suggest that such a methodology can be applied to other countries/regions and to other natural phenomena affecting the economy.
Keywords: morje, objavljeni prispevki na konferenci, morsko ribištvo, trajnostni razvoj, gospodarski aspekti, meduze, množično pojavljanje, distribucija, numerično modeliranje, klimatske spremembe, hipoteze, Pelagia noctiluca, Jadransko morje, gospodarske politike
Published in DiRROS: 26.03.2025; Views: 1146; Downloads: 839
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Abstract: Slovenija kot članica programa Združenih narodov za okolje (UNEP) in podpisnica Konvencije o varovanju Sredozemskega morja pred onesnaženjem (Barcelonska konvencija) aktivno sodeluje v programu Sredozemskega akcijskega načrta (MAP-Mediterranean Action Plan). Program Spremljanja stanja okolja (MED POL program) izvajamo s finančno pomočjo Ministrstva za okolje in prostor R Slovenije, Agencije RS za okolje. Poročilo vključuje rezultate mikrobioloških analiz kakovosti kopaliških vod, fizikalno-kemične in biološke analize morske vode za oceno stopnje evtrofikacije, rezultate policikličnih in aromatskih ogljikovodikov, kadmija in živega srebra v sedimentu in morskih organizmih (školjkah), oceno vnosa s kopenskih točkovnih virov onesnaženja v morje in rezultate analiz biomonitoringa za oceno bioloških posledic onesnaženja na morskih organizmih.
Keywords: varstvo narave, kakovost morja, kontrola kakovosti, morje, onesnaževanje, ekologija morja, biomonitoring, monitoring, evtrofikacijski monitoring, indeks trofičnosti, evtrofizacija, trofični indeks, Tržaški zaliv, Barcelonska konvencija, Jadransko morje
Published in DiRROS: 16.09.2024; Views: 2098; Downloads: 1229
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