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Alien polychaetes belonging to the genus Marenzelleria were recorded from the mouth of the Don River and Taganrog Bay in the Sea of Azov in February–March 2014. Morphological characteristics varied greatly and matched those of two species: M. neglecta and M. arctia. Some individuals did not match the descriptions of both species. A genetic study using different sequences (primarily COI, but also 16S, 28S, cytb and nuclear histone 3a) showed that only M. neglecta was present despite some morphological mismatches. A morphological description of the species according to the new data is presented, together with a revised table of variability of the key numeric characters. Since 2014, Marenzelleria has spread swiftly and become dominant in a considerable part of the Taganrog Bay, making up to 91% of the total abundance/biomass (6800 ind. m−2 and 31.2 g m−2, respectively). Monodominant sites were also present. Its occurrence is 100% in recent surveys. Such a sharp increase seems to be due to a lack of detritophages in the bay; this is supported by the fact that M. neglecta has not formed its specific assemblage. The community structure, if M. neglecta is excluded, is equal to that before the invasion. In the Sea of Azov itself, M. neglecta is not as abundant, but occurs up to the Strait of Kertch and at some sites in the Black Sea. Its spread further into the Black Sea seems possible, as well as into the Caspian Sea via the Volga-Don Canal.

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In 2009, a hitherto unknown Laonome species was found in the Canal Ghent-Terneuzen in the Netherlands and subsequently in other Dutch rivers, canals and estuaries. A few years later, more unknown Laonome specimens were found in the eastern part of the Baltic Sea and in the Don River estuary, Sea of Azov. Initially, it was assumed that these specimens could represent Laonome calida Capa, 2007, originally described from Australia. In the present study we examine all these unknown European Laonome specimens and compare these specimens with the type material of L. calida from Australia. This lead to two main results: First, all specimens from Europe have the same diagnostic characters and therefore belong to one species. This finding was also supported by the results of a correspondence analysis, and genetic analyses using four different DNA sequences (COI, 16S, 28S). Second, it turned out that the type material of L. calida contains two morphologically distinct groups of specimens. The holotype and 7 paratypes are similar to each other but differ significantly from the other also similar 16 paratypes, and from all European specimens. On the basis of these observations, the Laonome specimens from European waters are described here as L. xeprovala sp. nov. We also provide the characters of the branchial crown of three Laonome species for a prospective revision of this genus.

Seawater properties in two intense rings in the South Atlantic are considered. One ring separated from the Brazil Current and the other from the Malvinas Current. The analysis is based on the CTD casts and SADCP measurements from the onboard velocity profiler. The optical properties, chemical parameters, methane concentration, and biological properties such as primary production, plankton, and fish were also analyzed. Analysis of strong differences between the eddies is supplemented by observations of whales and birds in the region.

An assessment of the presentability of the biotopes and benthic communities of the northwestern part of the Utrish Nature Reserve marine area for the Caucasian Black Sea coast has been conducted. The literary and original data on the state of benthos in the area from the Kerch Strait to Adler were examined. The studied area of the Utrish Natural Reserve included habitats that are common along the coast (an active cliff, a narrow pebble beach, boulder deposits, rock bench and soft sediments). Only two of the three well-known Black Sea belt macrozoobenthic biocoenoses were observed along the northeastern Black Sea coast: the shallow-water «venus sand» and the deep-water «phaseolina silt». The third biocoenosis («mussel mud») was not noted neither in the reserve's area nor in the studied part of the shelf to the south of Novorossiysk. Of these three belts only «venus sand» was found in the Utrish Nature Reserve's marine area. The absence of the mussel belt in the studied area of the reserve is typical for the southern part of the North Caucasian coast in the current period and thus does not affect the presentability of the reserve's benthic ecosystem. The biocoenosis of the bivalves Pitar rudis -Gouldia minima was common at the muddy sand with shells in both reserve's and reference sites' middle-depths complex instead of the mussel belt which was typical for the 20 th century. Its boundary was 10 m deeper in the reserve compared to the reference sites. The absence of the Modiolula phaseolina belt in the area of the reserve could be explained by the insufficient width of the protected marine area (up to 52 m depth); due to this the deep-water complex in the reserve is actually represented by a narrow strip. Extension of the reserve's boundary over the depth of 70 m will include this biocoenosis into the Protected Area, which would significantly increase the presentability of the reserve's marine part for the North Caucasian coast. The biogeographical composition of the reserve's flora, its species diversity and structure in general corresponds to that of the whole region. The macrophyte zone consists of four belts: upper (0-2 m, Dictyota fasciola f. repens + Polysiphonia opaca + Ceramium ciliatum + Ulva compressa), upper mid (2-12 m, Cystoseira crinita + Cystoseira barbata -Cladostephus spongiosus -Ellisolandia elongata), lower mid (12-18 m, Phyllophora crispa, Codium vermilara and Bonnemaisonia hamifera), and the lower belt (below 18 m) formed by a recent invader, B. hamifera. The majority of species found in the reserve's marine area are common species of the Black Sea macrophytobenthos. However, the Utrish Nature Reserve includes more favourable habitats for macrophytes than most of the North Caucasian coast, because the typical macrophyte Cystoseira spp. have been noted at greater depths in the reserve, in comparison to the remaining shelf.

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Data on the fishes of the high-latitude Severnaya Zemlya archipelago (the North Land) is presented. The archipelago is located in the Arctic on the border between the Kara Sea and the Laptev Sea. The ichthyofauna of the archipelago has not been studied; therefore, even small collections are of interest. Fish samples were obtained during the expedition “Open Ocean: Arctic Archipelagos – 2019: Severnaya Zemlya”. In addition, the samples from this area in the collections of the Zoological Institute (ZIN) were studied, which have been received from polar expeditions to the Kara and Laptev seas during the entire era of polar research. The most significant fact is the discovery of mass accumulation of polar cod Boreogadus saida (Lepechin, 1774) larvae in Mikoyan Bay (Bolshevik Island), which gives evidence of important spawning grounds near Severnaya Zemlya. Indirect evidence of this can be found in the publications of polar explorers who overwintered on Severnaya Zemlya in the 1930s–1950s and have reported that the polar cod approaches the shores for spawning in August, in huge schools. The waters of Severnaya Zemlya represent the spawning area of polar cod in the central part of the Eurasian shelf, which is not mentioned in current literature. In addition to polar cod, a few more species are registered in samples from the coastal waters of the archipelago (depths to 38 m), rough hookear sculpin Artediellus scaber Knipowitsch, 1907, twohorn sculpin Icelus bicornis (Reinhardt, 1840) (family Cottidae), Liparis tunicatus Reinhardt, 1836, black-bellied snailfish L. cf. fabricii (Liparidae), Knipowich eelpout Gymnelus knipowitschi Chernova, 1999 (Zoarcidae) and three-spined stickleback Gasterosteus aculeatus (Linnaeus, 1758) (Gasterosteidae). In the deepwater straits, snailfish Careproctus sp. (174–234 m) and pale eelpout Lycodes pallidus Collett, 1879 (105–348 m) were found. The Arctic charr Salvelinus alpinus (Linnaeus, 1758) (Salmonidae) inhabits some lakes of the archipelago. This is the first finding of a three-spined stickleback in the east of the Kara Sea.