Development and interaction of ctenophores Beroe ovate Bruguière, 1789 and Mnemiopsis leidyi A. Agassiz, 1865 in the coastal zone of the Middle Caspian Sea

Aim. Analysis of the distribution and status of ctenophores Вeroe ovata and Mnemiopsis leidyi, and assessment of the parameters of their interaction in the Middle Caspian Sea.

Material and Methods. The material was obtained in the western and eastern parts of the Middle Caspian Sea in September–October 2022. Large ctenophores were collected using a big cone plankton net with a 0.5 m² opening and a 500 μm, mesh size. The number and size of large ctenophores were determined immediately after collection, larvae and eggs were counted in samples fixed with formalin to a final concentration of 4%. Zooplankton samples were collected by the Juday plankton net (0.1 m² opening, 180 μm mesh size).

Results. In September‐October 2022, a developed population of Вeroe ovata with active reproduction was recorded in the waters of the Middle Caspian Sea. The habitat area of B. ovata has significantly expanded to the north compared to 2021. Complete suppression of the Mnemiopsis population by the Beroe was observed on most of the western and eastern shelf, as well. The total number of Beroe reached 48 ind/m², biomass – 12 g/m². Single large individuals were found in the north of the Middle Caspian Sea at salinity 5.7 psu. The structure of mesozooplankton was still dominated by the small copepod Acartia tonsa.

Conclusion. New data indicate the active development of the Вeroe ovata in the Caspian Sea, which presents a fundamental challenge for the restoration of the Caspian ecosystem. The progressive adaptation of Beroe to the conditions of the Caspian Sea has led to its expansion to the north of the Middle Caspian Sea in areas with low salinity. A complete suppression of the M. Leidyi population by the new alien noted on most of the shelf indicates an increase in its pressure on the Mnemiopsis population compared to the corresponding period of 2021.

1. Ivanov V.P., Kamakin A.M., Ushivtzev V.B., Shiganova T.A., Zhukova O., Aladin N., Susan I., Wilson S.I., Harbison G. R., Dumont H.J. Simultaneous invasion of the Caspian Sea by two jellies Mnemiopsis and Aurelia. Journal Biological Invasions. 2000, no. 2, pp. 255–258.

2. Vostokov S.V., Ushivtsev V.B., Lisitsyn B.E., Solovyov D.M. Summer state of the population of Mnemiopsis leidyi – an invader in the Caspian Sea and its relation to habitat conditions. Okeanologiya [Oceanology]. 2004, vol. 44, no. 1, pp. 90–98. (In Russian)

3. Vostokov S.V., Gadgiev A.A., Vostokova A.S., Rabazanov N.I. The ctenophore Beroe cf. ovata in the Caspian Sea. The beginning of a new stage in the evolution of the Caspian ecosystem? South of Russia: ecology, development, 2020, vol. 15, no. 4, pp. 21–35. (In Russian) DOI: 10.18470/1992-1098-2020-421-35

4. Vostokov S.V., Vostokova A.S., Lobachev E.N., Tumalaeva O.M., Rabazanov N.I. Rahnama Haratbar Reza, Abtahi Behrooz, Tumalaeva O.M., Rabazanov N.I. New data on the ctenophore Beroe ovata, an invader to the Caspian Sea. South of Russia: ecology, development, 2021, vol. 16, no. 4, pp. 18–26. (In Russian) DOI: 10.18470/1992-1098-2021-4-18-26

5. Kamakin A.M., Chizenkova O.A., Zaizev V.F. Mnemiopsis leidyi impact on some trophical chains of the Caspian Sea. Yug Rossii: ekologiya, razvitie [South of Russia: ecology, development]. 2010, vol. 5, no. 2, pp. 67–74. (In Russian)

6. Kamakin A.M., Zaitsev V.F. Regularities of long-term and interseasonal dynamics of the ctenophore Mnemiopsisleidyi population in the Caspian Sea. Yug Rossii: ekologiya, razvitie [South of Russia: ecology, development]. 2012, vol. 7, no. 1, pp. 96–102. (In Russian)

7. Kamakin A.M., Khodorevskaya R.P. Impact of the alien species Mnemiopsis leidyi A. Agassiz, 1865 on fish of the Caspian Sea. Inland Water Biology, 2018, no. 2, pp. 51–56. (In Russian) DOI: 10.7868/S0320965218020067

8. Vinogradov M.E., Shushkina E.A., Anokhina L.L., Vostokov S.V., Kucheruk N.V., Lukasheva T.A. Mass development of the Beroe ovata eschocholtz near the North-Eastern coast of the Black Sea. Okeanologiya [Oceanology]. 2000, vol. 40, no. 1, pp. 52–55. (In Russian)

9. Vostokov S.V., Arashkevich E.G., Drits A.V., LukashevYu.F. Ecological and physiological characteristics of the ctenophore Beroe ovata in the coastal zone of the Black Sea: population, biomass, size characteristics of the population, behavior, nutrition, metabolism. Okeanologiya [Oceanology]. 2001, vol. 41, no. 1, pp. 109–115. (In Russian)

10. Arashkevich E.G., Anokhina L.L., Vostokov S.V., Luppova N.E. Reproductive strategy of the ctenophore Beroe ovata (Ctenophora. Tentaculata. Beroida) – a new invader in the Black Sea. Okeanologiya [Oceanology]. 2001, vol. 41, no. 2, pp. 116–120. (In Russian)

11. Vinogradov M.E., Shushkina E.A., Vostokov S.V., Vereshchaka A.L., Lukasheva T.A. Interaction between the populations of the ctenophores Mnemiopsis leidyi and Beroe ovata off the Caucasian coast of the Black sea. Oceanology. 2002, vol. 42, no. 5, pp. 661–669.

12. Luppova N.E., Arashkevich E.G. [Current state of the Black Sea macrozooplankton in the shelf zone of the sea]. In: Nazemnye i morskie ekosistemy Prichernomor'ya i ikh okhrana [Terrestrial and marine ecosystems of the black sea region and their protection]. 2018, pp. 90–91. (In Russian)

13. Shushkina E.A., Vinogradov M.E., Lukasheva T.A., Lebedeva L.P., Vostokov S.V. Comparative use of various plankton fishing tools for monitoring long-term changes in the black sea communities. Okeanologiya [Oceanology]. 2003, vol. 43, no. 5, pp. 744–750. (In Russian)

14. NASA's OceanColor Web. Available at: http://oceancolor.gsfc.nasa.gov (accesses 06.11.2022)

15. Lebedev S.A., Kostianoy A.G. Interannual variability of water exchange anomalies between the Northern, Middle and Southern Caspian based on satellite altimetry data. Ecologica Montenegrina, 2019, vol. 25, pp. 106–115.

16. Lebedev S.A., Kostianoy A.G., Ginzburg A.I. Dynamics of the Caspian Sea basing on the instrumental measurements, numerical modeling, and remote sensing data. In: “Applied aspects in geology, geophysics, and geoecology with the use of modern information technologies”, Materials of III International Conference, Maikop, 2015, pp. 146–179. (In Russian)