Sastav i raspodjela planktonskih ljuskara (Crustacea, Ostracoda) u Jadranskom moru - povijesna perspektiva

This study provides the first comprehensive results on species composition, seasonal and horizontal distribution of the planktonic ostracod community in the open waters of the whole Adriatic Sea. Samples were collected during the “Andrija Mohorovičić” oceanographic expedition (1974-1976) in all four seasons at 35 stations located along eight latitudinal transects in the northern, central and southern part of the Adriatic Sea. Fifteen ostracod species and two subspecies belonging to the family Halocyprididae were identified. The dominant species were Archiconchoecia striata, Porroecia spinirostris and Proceroecia macroprocera. Additionally, Paraconchoecia oblonga was recorded for the first time in the Adriatic Sea. The highest abundance and diversity of planktonic ostracods were found in the deep South Adriatic. Conversely, ostracods were scarce in the shallow North Adriatic area. As the transitional zone between these two regions, the Central Adriatic was characterized by high ostracod diversity, but a short period of dominance in the zooplankton assemblage. The horizontal distribution of planktonic ostracods in the Adriatic Sea could be linked to periodical ingressions of Eastern Mediterranean water masses and gyre currents, especially in the Central and the South Adriatic.Rad donosi prve sveobuhvatne rezultate o taksonomskom sastavu vrsta, sezonskoj i horizontalnoj raspodjeli zajednice planktonskih ljuskara u otvorenim vodama cijelog Jadranskog mora. Uzorci su prikupljeni tijekom oceanografske ekspedicije “Andrija Mohorovičić” (1974.-1976.) tijekom četiri godišnja doba na 35 postaja, raspoređenih u osam poprečnih transekata na sjevernom, srednjem i južnom dijelu Jadranskog mora. Taksonomski je određeno petnaest vrsta i dvije podvrste planktonskih ljuskara iz porodice Halocyprididae. Dominantne su vrste bile: Archiconchoecia striata, Porroecia spinirostris i Proceroecia macroprocera. Pored toga, vrsta Paraconchoecia oblonga je po prvi put zabilježena u Jadranskom moru. Najveća abundancija i bio-raznolikost ljuskara je zabilježena u dubokom južnom Jadranu, dok su bili rijetki u plitkom području sjevernog Jadrana. Kao prijelaznu zonu između ova dva područja, srednji Jadran karakterizira velika bio-raznolikost i kratkotrajna dominacija planktonskih ljuskara u zooplanktonskoj zajednici. Njihova horizontalna raspodjela u Jadranskom moru može se povezati s periodičnom ingresijom istočno-mediteranske vode i vrtložnim strujanjima, posebice u područjima srednjeg i južnog Jadrana

Ingresija hidromeduse Neotima lucullana (della chiaje, 1822) u ekosustavu estuarija rijeke Neretve (jugoistočni Jadran, Hrvatska)

Hydromedusa Neotima lucullana is an endemic species of the Mediterranean Sea. In this study we document the first numerous and permanent occurrence of N. lucullana in the estuary of the Neretva River, an unusual habitat for this typical marine species. We provide COI barcode sequence of this species, which is also first genetic sequence ever published of N. lucullana. Weekly data on the occurrence and abundance of N. lucullana were obtained from reports and records of autonomous divers and local fishermen in the area from Opuzen to Metković from mid-June to the end of October 2021. The individuals were always located in the layer above the bottom with salinity between 35.2 and 38.2. The diameters of the jellyfish bells ranged from 15 mm to 72 mm, most of them between 40 mm and 58 mm. Differential development of the gonads was observed in all specimens larger than 25 mm. In mid-June, the specimens were common but solitary. A week later, the jellyfish were more frequent and in smaller aggregations. From late June to mid-September, the jellyfish were constantly observed in larger aggregations. Toward the autumn, the number of individuals gradually decreased, and by the last week of October, only single individuals were observed. Our results indicate significant changes in the ecosystem of the Neretva estuary and confirm the observed composition of zooplankton communities dominated by marine species in summer and autumn.Hidromeduza Neotima lucullana je endemska vrsta Sredozemnog mora. Ovim istraživanjem dokumentiramo prve zapise o brojnoj i dugotrajnoj pojavi meduze N. lucullana u estuariju rijeke Neretve, neobičnom staništu za ovu tipično morsku vrstu. U sklopu ovog istraživanja dobivena je sekvenca podjedinice i citokrom oksidaze (COI), što je ujedno i prva genetička sekvenca ikad objavljena vrste N. lucullana. Tjedni podaci o pojavi i brojnosti N. lucullana dobiveni su na osnovi izvještaja i zapisa autonomnih ronilaca i lokalnih ribara na području od Opuzena do Metkovića od sredine lipnja do kraja listopada 2021. Jedinke meduza su uvijek bile u sloju iznad dna unutar vrijednosti saliniteta između 35,2 i 38,2. Promjer zvona meduza kretao se od 15 mm do 72 mm, glavnina između 40 mm i 58 mm. Diferencijalni razvoj spolnih žlijezda uočen je kod svih primjeraka većih od 25 mm. Sredinom lipnja jedinke su bile uobičajene, ali prisutne pojedinačno. Tjedan dana kasnije, meduze su bile često viđene i u manjim skupinama. Od kraja lipnja do sredine rujna, meduze su bile prisutne u većim agregacijama. Broj jedinki postupno se smanjivao prema jeseni i samo pojedinačni primjerci bili su uočeni tijekom posljednjeg tjedna listopada. Naši rezultati ukazuju na znatne promjene ekosustava donjeg toka rijeke Neretve što potvrđuje zabilježen sastav zooplanktonskih zajednica u kojima dominiraju morske vrste tijekom ljeti i jeseni

Composition and diel vertical distribution of euphausiid larvae (calyptopis stage) in the deep southern Adriatic

Summary: Diel changes in the vertical distribution and abundance of calyptopes were studied in the deepest area of the southern Adriatic over four seasons (July 2003, February 2004, October 2004, April 2009). Temperature variations were limited to the upper 100 m and salinity variations were small. Of previously known adult euphausiid species – 12 for the Adriatic (Gangai et al., 2012) and 13 for the Mediterranean (Mavidis et al., 2005) – calyptopes of 11 species of euphausiids were recorded. Abundance of calyptopes of all species was the highest in spring. Species were characterized according to their mean depth: surface (0–50 m), sub-surface (50–200 m), mesopelagic (200–800 m), or bathypelagic (800–1200 m) and vertical dispersion (scattered or non-scattered). Four diel patterns emerged: (i) nocturnal ascent to upper layers (Euphausia brevis, E. hemigibba, E. krohnii, Nematoscelis megalops, N. couchii), (ii) migration to upper layers at middle of the day and at night, and descent during the morning and evening (Stylocheiron maximum – only winter), (iii) weakly-migrating or non-migrating (S. longicorne), (iv) irregular migration independent of the day/night cycle (S. abbreviatum, S. maximum – during spring, summer and autumn, T. aequalis). Keywords: Euphausiid larvae, Mediterranean Sea, Secondary production, Vertical distribution, Weighted mean dept

Long-term Monitoring of Carnivorous Gelatinous Macrozooplankton in the Area of Dubrovnik-Neretva County (Croatia)

In the southern part the Adriatic, gelatinous macrozooplankton fauna is poorly known compared to the other taxa. Therefore, our goal was to collect and systematize all available phenological data and abundances of gelatinous organisms based on scientific surveys from 1996 to 2020 and a ”citizen science“ sighting program in the southern Croatian waters. The inter-annual variability and seasonality of planktonic Cnidaria and Ctenophora were described. A total of 590 reports was received from citizens, which summed up to result in 870 data together with the scientists’ records. In total, 15 species were recorded. Of these, scyphomedusa Pelagia noctiluca accounted for 34 %, followed by ctenophora Cestum veneris (19 %) and the scyphomedusa Cothylorhiza tuberculata (17 %). Mass occurrence was most frequently found in P. noctiluca and then in C. tuberculata and C. veneris. Isolated mass occurrence was recorded for the freshwater hydromedusa Craspedacusta sowerbii, found in Lake Kuti near the mouth of the Neretva River, and for the scyphomedusa Aurelia cf. solida. The three species A. solida, Mnemiopsis leidyi and C. sowerbii are not native to European waters. Considered that alien species are invading the Adriatic Sea and human impact and global warming are increasing, it is crucial to carefully monitor the occurrence of gelatinous zooplankton taxa and to conduct studies focused on deciphering their ecological impact in marine ecosystems. Therefore, our empirical analysis of 25 years of observations provides essential information on the variation of gelatinous zooplankton in the Southern Adriatic region