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This study presents an inventory of planktonic cnidarian species collected in Algerian coastal waters (1°10’00” W - 6°52’37” E and 35°37’42” N - 37°01’16” N) from May 2012 to February 2017. The aim was to analyse the qualitative distribution and identify the main components of this gelatinous fauna in different coastal ecosystems in western, central and eastern regions. A total of 60 taxa of planktonic cnidarians were identified, including 57 hydrozoans and three scyphozoans. The class Hydrozoa were represented by 34 hydromedusae, primarily belonging to orders Anthoathecata (15 taxa) and Siphonophorae (23 taxa). Several reported hydrozoan species were recorded for the first time in the southwestern Mediterranean Sea. These new regional records include the hydromedusae Kantiella enigmatica, Leuckartiara octona, Proboscidactyla ornata, Cunina globosa, Lovenella cirrata, Cirrholovenia tetranema, Phialella quadrata, Homoeonema platygonon and the siphonophore Forskalia contorta. Seasonal fluctuations were observed in biodiversity, with the highest species richness in spring and summer. The most common species are the calycophorous siphonophores Abylopsis tetragona, Muggiaea atlantica, Lensia subtilis Muggiaea kochii and the holoplanktonic medusae Aglaura hemistoma, Rhopalonema velatum, Solmundella bitentaculata, Liriope tetraphylla and Pelagia noctiluca. The species’ occurrence frequency exhibited seasonal and spatial variability. These distribution patterns were primarily determined by meroplanktonic hydrozoans (Anthoathecata and Leptothecata). [ABSTRACT FROM AUTHOR]

Two jellyfish species are documented for the first time from the Lebanese waters. A string jellyfish, siphonophore, Apolemia cf. uvaria, was observed first on 25 May 1993, at 5 m depth, off Tripoli (north of Lebanon) and recently on 25 April 2021 photographed off Saida (south Lebanon) at 16 m depth. The other species, a rare ctenophore, venus girdle, Cestum veneris, was observed and photographed at around 2 m depth off Tyre (south Lebanon), on 4 March 2021 [ABSTRACT FROM AUTHOR]

Abstract This study analysed the distribution and abundance of both polygastric (asexual) and gonophores of the calycophoran siphonophores Muggiaea atlantica and Muggiaea kochii in the Mondego estuary (Portugal), as well as the influence of local environment and prey availability on the observed patterns. Samples were collected in three different zones of the estuary, from December 2013 to November 2015. In general, both species nectophores and total gonophores followed a similar trend, with higher abundances during spring-summer periods and increased densities in the downstream areas of the estuary, where the marine influence is stronger. Inter-annual differences occurred mainly for M. atlantica nectophores, which showed higher abundances in 2015, particularly in the upstream areas. Both species displayed a shift in the annual peak abundance, from bimodal in 2014 to unimodal in 2015. Patterns observed were not only strongly related with an increase of the marine influence in the estuary, but also with the presence of zooplanktonic prey, such as cirripede cypris , calanoid nauplius , Poecilostomatoida, and copepodites of Cyclopoida. This study represents a step towards a better knowledge of the biology and ecology of siphonophores. [ABSTRACT FROM AUTHOR]

Siphonophorae were collected monthly in 2009 at four stations with different hydrographic characteristics at Bay of Boka Kotorska in the Southern Adriatic. Three of these stations were placed in the shallow part of the inner bays near the shellfish farm, and four in the Bay of Kotor, Bay of Risan, Bay of Tivat and Bay of Herceg Novi. The special ecological conditions in the Bay of Boka Kotorska are reflected on taxonomic structure, distribution and abundance, both of individual species and the zooplankton as a whole. In this paper we present the hydrographic data of Boka Kotorska Bay, together with data on presence, abundance and distribution of the six species by three genera: Abylopsis tetragona (Otto), Lensia conoidaea (Keferstein-Ehlers), Lensia subtilis (Chun), Lensia fowleri (Bigelow), Lensia multicristata (Moser), Muggiaea kochi (Will) and other Siphonophorae sp. Results of this research include biological monitoring at the bay, following certain species within the zooplankton diversity and communities. [ABSTRACT FROM AUTHOR]

The impacts of environmental changes and mangrove disturbance on the gelatinous zooplankton community structure were investigated monthly for one annual cycle at six stations in three estuaries in Matang, Malaysia. Tiram, Tinggi, and Sepetang estuaries were classified based on the Mangrove Quality Index (MQI) to represent the least (MQI 5 = excellent), moderately (MQI 4 = good), and highly disturbed (MQI 2 = bad) areas, respectively. Among the gelatinous zooplankton species, the holoplanktonic ctenophore, Pukia ohtsukai (formed 56%–58% of the total gelatinous zooplankton), was the most dominant species and showed increased densities with the increasing level of disturbance. On the other hand, a hydrozoan, Blackfordia sp. (39%–43%), which needs suitable substrates for the survival of polyploids, was found to be most abundant in the moderately disturbed area, indicating low densities in areas with too little or too much disturbance. Salinity, a parameter influenced by river discharge and tidal changes, was identified as the main environmental factor affecting the species' seasonal variability. The dry season was associated with an increase in gelatinous zooplankton density and prevalence of marine species. Also, factors related to water clarity (turbidity, transparency, and suspended solids) and nutrients (nitrogen and phosphorus) explained 91% of the variables that affected the gelatinous zooplankton community structure. The species diversity (H ′) in the least and moderately disturbed areas were significantly higher than in the highly disturbed estuary. In contrast, the highest mean density was recorded in the highly disturbed estuary (34.4 ± 19.8 inds. m−3) followed by the moderately (21.6 ± 6.1 inds. m−3) and the least disturbed areas (9.7 ± 4.1 inds. m−3). The present study suggested that the gelatinous zooplankton biodiversity declines and the abundance escalates with increasing disturbance levels. [Display omitted] • Gelatinous zooplankton diversity declined with increasing disturbance level. • Gelatinous zooplankton abundance escalated with increasing disturbance level. • The dominant holoplanktonic ctenophore showed increasing density with disturbance level. • The density of the meroplanktonic hydrozoan was lowest in areas with too little or too much disturbance. • Factors related to turbidity and nutrients explained 91% of gelatinous zooplankton variability. [ABSTRACT FROM AUTHOR]

Some studies have suggested that pelagic cnidarians are important components of the Southern Ocean ecosystem due to their high abundance and diversity and their high predatory effects, although little information on these animals is available. Thus, we examined the spatial distribution of pelagic cnidarians from the oceanic to neritic zone off Adélie Land, East Antarctica. Discrete depth sampling was conducted from the surface to 2,000 m depth from late January to early February 2008. In total, 3347 individuals representing 45 species/taxa from eight orders were collected. Cluster analysis revealed three major clusters: (1) an epipelagic group in the oceanic zone composed mainly of Pegantha martagon, the abundance and species diversity of which were very low; (2) a meso- and bathy-pelagic group characterised by high abundance and species diversity with dominance of Dimophyes arctica, Vogtia serrata, and Halicreas minimum; and (3) a neritic group represented by a high abundance of Diphyes antarctica. Cnidarian communities in the epipelagic zone were divided by hydrographic structures such as the Southern Boundary of the Antarctic Circumpolar Current and Antarctic Slope Front, whereas those in the meso- and bathy-pelagic layers dominated by circumpolar deep water were relatively stable with higher diversity throughout the oceanic zone. [ABSTRACT FROM AUTHOR]

The special location (40-42°S in the Southwestern Atlantic Ocean) and the hydrodynamic regime (limited water exchange with open ocean) in San Matías Gulf ( Argentina) seem to produce a particular fauna of planktonic cnidarians whose their abundances are mainly shaped by the Gulf circulation. Four oceanographic cruises, covering 93 stations in three different seasons during 2007 and 2008 were carried out to quantify species richness and abundance, as well as to analyse the distribution of these cnidarians. We identified 20 species of hydromedusae and one siphonophore, increasing the total number of hydromedusae for the area to 23. This value is similar to the one found in the abutting Argentine continental shelf (20), but with a different assemblage composition. Hydromedusae abundances found were low, except for a bloom of the Leptomedusa Obelia spp. during the cold season. The only siphonophore found in the area, Pyrostephos vanhoeffeni, has previously been thought to be endemic to Antarctic and sub- Antarctic waters, this being the first record for temperate waters of the Southwest Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Abstract: The impact of biological, hydrodynamic and large scale climatic variables on the jellyfish community of Mondego estuary was evaluated from 2003 to 2010. Plankton samples were collected at the downstream part of the estuary. Siphonophora Muggiaea atlantica and Diphyes spp. were the main jellyfish species. Jellyfish density was generally higher in summer and since 2005 densities had increased. Summer community analysis pointed out Acartia clausi, estuarine temperature and salinity as the main driven forces for the assemblage''s structure. Also, Chl a, estuarine salinity, runoff and SST were identified as the major environmental factors influencing the siphonophores summer interannual variability. Temperature influenced directly and indirectly the community and fluctuation of jellyfish blooms in the Mondego estuary. This study represents a contribution to a better knowledge of the gelatinous plankton communities in small temperate estuaries. [Copyright &y& Elsevier]