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Povzetek: Morning, midday, evening and night repetitive sampling was used to demonstrate calycophoran diel vertical migration (DVM) at a fixed station in the oligotrophic southern Adriatic Sea at 8 depth intervals. Of 20 calycophoran species collected, most of them inhabited layers of specific temperature and light intensity, and migrated during the night. The deep species Kephyes ovata is primarily non-migratory. Typical nocturnal movements to the surface were recorded for Lensia conoidea and sphaeronectes koellikeri. Lensia subtilis and eudoxoides spiralis migrated toward the surface in the evening but sank deeper at night. Lensia meteori and Lensia fowleri reached upper layers at midday. The DVM of sphaeronectes irregularis was irregular and independent of diel light patterns. Though low in numbers, some calycophorans were found above the thermocline at night. For mesopelagic species, however, higher summer surface temperatures proved an effective barrier to migration above 100 m. Thus, certain species could be represented as key species of planktonic cnidarian assemblages found within a certain depth range. Though not homogenous, and while some undertake nocturnal migrations in both directions, all are interrelated by preferences of bathymetric distribution and specific DVM behavior.
Ključne besede: sea, medusae, biological research, abundance, bathimetric distribution, siphonophora, calycophoran siphonophores, composition, Adriatic Sea
Objavljeno v DiRROS: 26.03.2025; Ogledov: 737; Prenosov: 524
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Povzetek: Deskriptor 1: Biotska raznovrstnost se ohranja. Kakovost in prisotnost habitatov ter razporeditev in številčnost vrst so v skladu s prevladujočimi fiziografskimi, geografskimi in podnebnimi pogoji. »Presojo je treba opraviti na več ekoloških ravneh: na ravni ekosistemov, habitatov (vključno z njimi povezanimi združbami na nivoju biotopov) in vrst, ki so upoštevane v strukturi tega dela ob upoštevanju točke 2 dela A. Za nekatere vidike tega deskriptorja je potrebna dodatna znanstvena in tehnična podpora. Pri obravnavi širšega obsega deskriptorja je treba ob upoštevanju Priloge III k Direktivi 2008/56/ES določiti prioritete med elementi biotske raznovrstnosti (vrste, habitati in ekosistemi). To omogoča prepoznavanje tistih elementov in območij, kjer vplivi in grožnje nastajajo, poleg tega pa podpira opredelitev ustreznih kazalcev med izbranimi merili, primernimi za zadevna območja in elemente biotske raznovrstnosti. Obveznost regionalnega sodelovanja iz členov 5 in 6 Direktive 2008/56/ES je neposredno povezana z izbiro elementov biotske raznovrstnosti znotraj regij, podregij in pododdelkov, kjer je mogoče, pa tudi z vzpostavitvijo referenčnih razmer v skladu s Prilogo IV k Direktivi 2008/56/ES. Modeliranje z uporabo platforme geografskega informacijskega sistema je lahko uporabna podlaga za določanje območja razširjenosti elementov biotske raznovrstnosti ter človekovih dejavnosti in pritiskov zaradi teh dejavnosti, ob upoštevanju, da se vse mogoče zajete napake ustrezno ocenijo in opišejo ob uporabi rezultatov. Ti podatki so pogoj za ekosistemsko upravljanje človekovih dejavnosti in za razvoj s tem povezanih prostorskih orodij.«
Ključne besede: morje, obalno morje, onesnaževanje morja, plankton, hranilne snovi, ekološki parametri, onesnažila, onesnaževalci, biocenoze, okvirna direktiva o morski strategiji, poročila, onesnaženost, kvaliteta okolja, morska strategija, deskriptorji
Objavljeno v DiRROS: 16.09.2024; Ogledov: 1738; Prenosov: 1079
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Povzetek: This manuscript presents four new observations of the jellyfish Mawia benovici in the Adriatic Sea. This new species was recently identified as Pelagia benovici by Piraino et al. (2014) and then placed in the new genus Mawia by Avian et al. 2016. This species is rare and is almost exclusively observed in the Adriatic Sea. Interestingly, the majority of observations refer to males only. Few studies have addressed the issue of sex determination in Syphozoa in particular, as sex identity can only be determined at the medusa stage. Unfortunately, the rarity of M. benovici and the lack of female specimens have so far prevented indispensable laboratory studies to clarify its life cycle. Still, we tried to propose an explanation for our field observations.
Ključne besede: jellyfish, sex ratio, Mediterranean Sea
Objavljeno v DiRROS: 06.08.2024; Ogledov: 1211; Prenosov: 968
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Povzetek: Aurelia aurita s.l. is the most widespread scyphozoan jellyfish that recurrently appear “en mass” and forms large aggregations mainly in coastal waters, embayments and estuaries. Beside anthropogenic factors controlling jellyfish populations climate change may play an important role. The aim of this study was to assess whether climate-related factors in absence of other anthropogenically induced stressor influence medusae size. We investigated seasonal and interannual changes in the size of Aurelia in a “jelly lake” in the National Park of Mljet Island (Croatia) where minimal human impact on the environment makes the Veliko Jezero a natural mesocosm for understanding the impact of climate change on the Aurelia population. The observed changes suggest Aurelia medusa population response to changing environment, in particular to enhanced temperature, by reduced body sizes. Comparison of Aurelia population dynamics from different regions in the Mediterranean Sea revealed the unique feature of the Veliko Jezero population. Despite the similarity of the environmental windows of medusae occurrences in the Veliko Jezero and regions in the Mediterranean Sea, medusae in the Veliko Jezero are present all year round. It seems that the lake bathymetry enables medusae to vertically migrate to deeper and cooler water layer, avoiding the limiting temperatures developed in the upper layer during the summer. These conditions may prolong the Aurelia medusae life span and together with continuous strobilation support the stability of the Aurelia medusae population all year round.
Ključne besede: Mediterraneum, moon jellyfish, Adriatic Sea, South Adriatic Sea, marine lakes, Aurelia spp, climate-related factor, Mediterranean Sea, marine research, population dynamics
Objavljeno v DiRROS: 05.08.2024; Ogledov: 1042; Prenosov: 530
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Povzetek: One of the obstacles to detecting regional trends in jellyfish populations is the lack of a defined baseline. In the Adriatic Sea, the jellyfish fauna (Scyphozoa and Ctenophora) is poorly studied compared to other taxa. Therefore, our goal was to collect and systematize all available data and provide a baseline for future studies. Here we present phenological data and relative abundances of jellyfish based on 2010–2019 scientific surveys and a “citizen science” sighting program along the eastern Adriatic. Inter-annual variability, seasonality and spatial distribution patterns of Scyphomedusae and Ctenophore species were described and compared with existing historical literature. Mass occurrences with a clear seasonal pattern and related to the geographical location were observed for meroplanktonic Scyphomedusae Aurelia solida, Rhizostoma pulmo, and to a lesser extent Chrysaora hysoscella, Cotylorhiza tuberculata and Discomedusa lobata. Holoplanktonic Pelagia noctiluca also formed large aggregations, which were seasonally less predictable and restricted to the central and southern Adriatic. Four species of Ctenophora produced blooms limited to a few areas: Bolinopsis vitrea, Leucothea multicornis, Cestum veneris and the non-native Mnemiopsis leidyi. However, differences between Adriatic subregions have become less pronounced since 2014. Our results suggest that gelatinous organisms are assuming an increasingly important role in the Adriatic ecosystem, which may alter the balance of the food web and lead to harmful and undesirable effects.
Ključne besede: jellyfish phenology, hydrobiology, long-term changes, Mediterranean Sea
Objavljeno v DiRROS: 19.07.2024; Ogledov: 1155; Prenosov: 725
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