New INTRODUCED SPECIE IN THE Caspian Sea – MNEMIOPSIS LEIDYI (A. AGASSIZ)

During last years the ecosystem of Caspian Sea is undergoing acute changes caused by sea level fluctuations, anthropogenic pollution and introduction of new species from Azov-Black Sea basin. Those changes resulted in extinction of some species (for instance some species from Dreissena genus – Dr.elata, Dr. caspia because of enormous development of Mediterranean specie Mytilaster lineatus) and tremendous increase of Acartia clausi, Balanus improvisus etc. For instance in 1954 Balanus improvisus was accidentally introduced to the Caspian Sea, and during short period of time has massively evolved on underwater stones, tree stems, piles, various hydro technical structures, vessels’ bottoms, mollusks’ shells, testas of crawfishes and crabs. Its bio mass in benthos amount to 8.1 – 64.0 gr/sq.m., and on offshore oil installations – 4.7 kg/sq.m (1).

In 1957 Pleopis polyphemoides appeared in the benthos of Caspian Sea and in 1981 – Acartia clausi. The density of the latter on Ignatia Stone – Cheleken come to 30 thousand pieces / cub.m. and biomass reaches is equal to 99.4 mg/cub m (6).

In spring 2000, in Mid and Southern Caspian Sea we discovered new, previously unregistered in the Caspian Sea – Mnemiopsis leidyi, which most likely was introduced in the Caspian Sea in 1998-1999 from Azov-Black Sea basin through Volga-Don canal brought with ballast water of vessels. In 1982 M.leidyi was introduced in Black Sea with ballast waters of grain transporting ships making direct shuttling between US ports and Odessa (8) and in summer of 1988 it was detected in Azov Sea (10).

M.leidyi is widely spread from Arctic to Antarctic, including tropic waters. Mnemiopsis genus is endemic of Atlantic coasts of Northern America from Florida to Chesapeake bay, where it is represented by 3 species. All of them inhabit both in oceanic and in salty waters (9).

We registered M.leidyi in Western part of Mid Caspian Sea M.leidyi in May 2000, near Nabran settlement, in the Northern Absheron gulf, coastal waters of islands Pirallahi (Artem), Oil Stones, and in western part of Southern Caspian – from Shikhov to Bandovan areas, on offshore oil fields Chirag, Azeri, Nakhichevan, Oguz, on gas field Shakh-Deniz, along pipeline Chirag-Sngachal terminal and in waters of Sangachal terminal (scheme).

Recently invaded in Caspian Sea M.leidyi has developed in this water reservoir, therefore there appeared a need for investigation of its biology and ecology.

Material and methodology. To assess the size and biomass of M.leidyi in western part of Mid and South Caspian and its impact on the structure of animal plankton, there were taken some samples of animal plankton from 120 stations located in the shallow coastal waters on the depth of up to 170 meters in May-December 2000 and January-March 2001. The size and structure population of M.leidyi were evaluated on the basis of catches by Jedi net from gas # 38.

Identification of its body’s raw weight has been accomplished by standard method (3).

Quantitative development. In the western part of Mid and South Caspian the length of M.leidyi is 115 mm, its width – 40 mm. and weight – 3.5 gr. In the Black Sea its length mounts to 120 mm and weight - 2871 mg of dry substance (12).

In may 200, near island Oil Stones, the density of M.leidyi ranged from 50 to 120 pieces/ cub.m. and in July of the same year at Shakh-deniz field – 250 pieces/cub.m. In October along the Shikhov – Bandovan zone its concentration was ranging from 142 to 1196 pieces/cub.m. and biomass ranged from 29.9 to 251.2 mg/cub.m. (table). The highest indicators of concentrations and biomass of M.leidyi were monitored in the waters of Sangachal terminal in the samples of animal plankton taken near Cape Sangachal in December 2000 and January-March 2001 no M.leidyi was identified.

At all Mid and South Caspian areas, biomass of M.leidyi exceeded the biomass of the rest of animal plankton. Biomass of fodder animal plankton declined 1.1-15.7 times in comparison with previous years. Almost the entire population of M.leidyi inhabited upper water layer at the depth of 10-25 m; only once in the area of Chirag oilfield there were detected 4 M.leidyi individual of M.leidyi below the temperature jump level. In October samples of animal plankton there were a plenty of young M.leidyi individuals 10-15 mm. in length. Mature individuals of M.leidyi live away from the shores, and young individuals live in coastal shallow waters. Water temperature has a great impact on quantitative distribution of Mnemiopsis. M.leidyi is euryhaline and eurythermic organism.

Reproduction.M.leidyi has a syngenesis reproduction. It reproduces in the Black Sea throughout year. It runs to maximum level in July-August and minimal – end of April – beginning of May (4). According to A.N. Grishin (2), they did not monitor maximum quantity of young M.leidyi individuals in July-August, but I May and September a large number of youngsters was recorded. He has also mentioned that larvae born in late autumn survive during winter and continue their grow in early spring.

In South Caspian, reproduction of M.leidyi was registered in August-September. Mnemiopsis larvae winter on the bottom of the sea.

Nutrition.M.leidyi is quite a voracious predator, has two tentacles which are provided with side branches; they can considerably stretch and shorten. The tentacles are supplied with a large number of sticky cells (7). Numerous Belanus improvisus and Acartia clausi as well as larvae of bottom invertebrates stick to those cells. Until the pray does not run into catching structures of Ctenophore it is not caught, therefore daily nutrition of Ctenophore depends on concentration of fodder organisms in its surroundings, because it is a passive predator.

Average indicators of animal plankton and Mnemiopsis leidyi
In Mid and South Caspian Sea (pieces/g * cub.m.)

In the Black Sea young M.leidyi consume mainly - copepods and adult individuals – cladocerans (11). Its nutrition includes very often Acartia clausi of all ages. Second place in terms of nourishment frequency (around 75 %) is occupied by Pseudocalanus elongatus, Paracalanus parvus, Oithona similis and Podon leucarti, which are dominating in plankton. Third place in term of nourishment frequency and on first place in term of weight is occupied by Calanus helgolandicus (2).

In laboratory environment M.leidyi may consume Pseudobrachia, its own young individuals, fish bits, young jellyfishes and particularly willingly Calanus helgolandicus and other copepods (5).

Nourishment of M.leidyi is twice less when concentration of nutrition is 1460 mg/l, and in case if concentration of Calanus ponticus is less than 3 pieces/l or 0.6 mg/l of dry substances the nutrition of Ctenophore is actually suspended (12,13).

Nauplius copepods and shellfish, Bivalvia, adult copepods Acartia sp. And Oithona sp are dominating in nourishment of M.leidyi inhabiting in waters from New England till Mexican gulf. It also eats fish eggs and larvae (16).

We have identified that the nourishment of M.leidyi in Caspian Sea includes the following nourishment objects presented in the descending raw dependent on their frequency: Acartia clausi – 32.4, Eurythemora – 11.6, Balanus improvisus – 10.0, Bivalvia – 9.7, Pleopsis polyphemoids – 8.4, Polyphemus exigus – 6.7. Thus nutrition of M.leidyi often represented by acaridan, eurotemora and larvae of invertebrates. The frequency of other components did not exceed 10 %.

Discussion of results.Reduction of biomass of shellfishes serving as a feed for M.leidyi will notably change trophic structure of animal plankton of Caspian Sea. It will lead to an abrupt increase of ctenophore role played in animal plankton and declining of animal plankton reproduction. First few years it may seriously impact on reduction of the size and biomass of animal plankton, followed by recess.

It is known that in native waters, by the end of summer, ctenophore has very high concentrations amounting to tens and hundreds of pieces per cubic meter. At the same time they consume almost all shellfishes and other mesoplankton including other types of ctenophore that makes them an important factor reducing water reservoir nutrition and size of fish populations. Thus a considerable development of M.leidyi in the Caspian Sea may cause to dwindling of sprats and some herrings, which eat animal plankton, and consequently affect white surgeons, which in its turn, consume sprats and herrings as a major fodder. Caspian seals will also suffer from the lack of fodder as the key role in their nourishment is played b sprats and shellfishes.

References

1. Bagirov R.M. Azov-Black Sea invaders in benthos and biofouling of Caspian Sea. – Report, discussion, Baku, 1989, page number 44.

2. Grishin A. N.Peculiarities of Mnemiopsis leidyi (A.Agassiz) in the Black Sea conditions Gidrob magazine 2000, pages 24-31.

3. Vinogradov M.E.Shushkina E.A. Functioning of plankton communities epipalagialium of ocean

4. Vinogradov M.E.Sapognikova V.V, Shushkina E.A. Black Sea Ecosystem M.Nauka, 1992, page 110

5. Vinogradov M.E.Shushkina E.A, E.I.Musayeva, Sorokin U.I. New migrant in Black Sea – Mnemiopsis Leidyi (A.Agassiz) (Ctenophora: Lobata) – Ocean Science, 1989, 29, 2, pages 293-299.

6. Kurashova E.K., Abdullayeva N.M. Acartia clausi (Giesbrecht) (Calanoida Acartiidae) in Caspian Sea – Zoology magazine, 1984, 63, 6, pages 931-933.

7. Natali V.F.Invertebrates zoology – M. 1963, page 522

8. Pereladov M.V.Some observations of biocenosis changes in Sudak gulf of Black Sea – Thesis Report, III USSR conference on marine biology, Sevastopol 1988, 1, pages 237-238.

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10. Studenikina E.I, Volkovic S.P, Mirozyan I.A., Luts G.I. Mnemiopsis leidyi in Azov Sea – Ocean Science, 1991, 31, 6, pages 981-985.

11. Tsikhon-Lukanina E.A. Reznichenko O.G. Nourishment features of Mnemiopsis individuals of different size in Black Sea. – Ocean Science, 1991, 31, 3, pages 442-446

12. Tsikhon-Lukanina E.A. Reznichenko O.G., Lukasheva T.A. Quantitative nourishment patterns of Black Sea Mnemiopsis leidyi – Ocean Science, 1991, 31, 3, pages 272-276

13. Tsikhon-Lukanina E.A. Reznichenko O.G. What Mnemiopsis feed in the coastal waters of Black Sea – Ocean Science, 1992, 32, 4, pages 724-729.

14. Kremer P.Population dynamics and ecological energetic of a pulsed zooplankton predator, the Ctenophore Mnemiopsis leidyi – Estuarine Processes, 1976, 1, 4, pages 197-215.

15. Kremer P., Scott N.Distribution and abundance of the ctenophore Mnemiopsis leidyi in Narragansett bay. Estuarine and Coast Marine Science, 1976, 4, 6, pages 627-639.

16. Russel F.S.The seasonal abundance and distribution of the pelagic young of teleostean fishes caught in the ring trawl in offshore waters in the Plymouth area – J.Mar, Biological Association, UK, 1935, 20, 2, pages 147-180.