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Ecological Determination of the New - ovata Invasion in the Black Sea

Asen S.Konsulov, Lyudmila T.Kamburska

Institute o f Oceanology, Bulgarian Academy of Sciences (Varna)

Introduction. In results of the high Black Sea environment which ensures the . ..nophication and antropic impact during best conditions for development and the last twenty years [15] the Black Sea reproduction of the invader M. leidyi. Despite i ''mes favourable for the development of of the annual and seasonal fluctuation this many invaders (Zatzev, Mamaev, species has been the dominant component 1997). The stable settlement of some of them in the Black Sea ecosystem during the last leads directly to drastic changes in the 10 years with maximal abundance in fauna diversity and its quantitative 1988-1989(Bogdanova, Konsulov, development (Konsulov, Kamburska, 1993) and minimal abundance in 1991-1992 1997) and indirectly influences the other (Konsulov, Kamburska, 1997). parts in the food chain. This concerns in Feeding on Zooplankton M. leidyi appears great extent the representatives of as an important rival of the pelagic fish, Ctenophora which are important carnivores which results in a decrease of their in planktonic food chains (Fraser, 1962). commercial resources (Nelson, 1925). On Until 1985 only one representative of class Ctenophora was known as a part of the Black sea plankton covopoúXwn- pileus (= Pleurobrachia rhodopis). This species has never had mass development (Konsulov, 1991). In spring of 1986, 20-30 miles east from Cape Emine, a new one for the time being species of Ctenophora was identified as leidyi (Konsulov, 1989).M. leidyi has arrived through ship ballast waters from North Atlantic (Vinogradov, 1989 et al.). The reason for this species settlement and its development into the Black Sea basin Fig. 1. Beroe ovata with engulfed individual is the high degree of eutrophication of the o f Mnemiopsis leidyi - 196-

the other hand elimination of herbivorous to be exclusively carnivorous on other Zooplankton (especially C opepoda) ctenophores (G reeve, 1970). Nelson increases the phytoplankton abundance and (Nelson, 1925) reports that Beroe ovata biomass (Deason, Smayda, 1982) feeds only on M. leidyi species. Our respectively to a high level of eutrophication. investigation reveal that from 2 to Because of the serious disturbances in the 7 individuals ofM. leidyi with size 10-20 mm pelagic ecosystem caused after the mass have been discovered in the guts of the live development of this species reaching total samples of Beroe ovata. Pieces of the prey biomass more than 5 kg/m2 (M a I a s h e v , with size 10-40 mm were also found as well Archipov, 1992) GESAMP outline a as fragments of its sexual arches. The strategy for its control in the Black Sea underwater photographs which helped for (GESAMP, 1997). One of the proporsals is the identification of the species from class to apply a biological control through Ctenophora completely confirmed the introduction of its predator of the genus results of the laboratory observations for the Beroe. This item has advantages and presence of M. leidyi in Beroe ovata’s disadvantages. This measure is unnecessary stomach contents [Fig. 1]. If the prey is because of the natural invasion of Beroe smaller than the Beroe ovata, it is completely ovata in the Black Sea. In October 1997, in engulfed. Small individuals of Beroe cut with the vicinity of Shabla, a new species lips parts from the tissue of the M. leidyi belonging to class Ctenophora and identified (Swanberg, 1970). as Beroe ovata was located. The technical mechanism for transfer of The aim of this paper is to present the main larvae and adult representatives of M. leidyi reason for the migration of Beroe ovata into and Beroe ovata is one and the same-ballast the Black Sea waters. Up to now this waters. Despite of this their invasion did not predatory species has not been reported for occur simultaneously but within a time gap the basin’s fauna. of 10 years. Materials and Methods.The samples for The analysis of the data referring analysis and identification were collected by Zooplankton state, M. leidyi quantity and means of SCUBA diving technique. Species eutrophication degree shows that in 1986 were gathered in a glass vessel and moved when M. leidyi was discovered in the Black live to the laboratory. During sampling Sea waters, the zooplankton biomass was operations representatives of the species 192.36 mg/m3 and the number of ctenophora were shot with underwater camera in their was 8 ind/m3. In 1990 the zooplankton natural environment as they move and eat. biomass decreased to 135.84 mg/m3and the They were identified under laboratory number ofM. leidyi increased to 85-150 ind/ conditions after observations of live m3 (Bogdanova, Konsulov, 1993). individuals and species fixed in 4 % An increasing trend of zooplankton biomass formalin solution and 3 % gluteraldehyde. (about 210 mg/m3) was noticed after 1992 Results and Discussion. The results of when the number of M. leidyi was very morphostructural analysis of the Ctenophora low-6 ind/m3. In the period 1995-1997 its allow us to assume that this is a newcomer average abundance was 277 ind/m3 in the Black Sea known as Beroe ovata (Konsulov, Kamburska, 1997). species. Its body is egg-shaped with well Under these ecological and trophic conditions expressed mouth-circling rim. Ciliated belts of the Black Sea shallow shelf zone off the are laid meredionally and linked with Bulgarian coast the same year we have crosswise arches. discovered adult and juvenile stages of Beroe It is well known .that the species of the ovata. The reason for this is the highM. leidyi genus Beroe have previously been considered abundance which Beroe ovata uses to feed - 197-

on, give lis enough grounds to assume that considerations rise some questions : whether the invasion of the new for the Black Sea wolud settle permanently and whether a Ctenophora is trophicaliy determined. species feeding on it will migrate in the Black Eliminating one of the reason for a high Sea, because local predators of Beroe ovata level of eutrophication-Mnemfo/wE leidyi, the arc not known? new ctenophora species Beroe ovata could Acknowledgments.The authors are grateful reach high biomass.This can lead to a new to our colleague the underwater photographer disturbance in the Black Sea ecosystem as Eng. Lyubomir Klisurov for the materials and mass development of ctenophores drastically photos. We would like to thank the staff of modifies the structure of an otherwise stable „Marine ecology and biology“ Department, community (Bishop, 1967). The above IO-BAS for the useful comments.

References Bishop, J. W. 1967. Feeding rates of the the Bulgarian Coast. D.Sc. Thesis (in Ctenophore Mnemiopsis leidyi.-In: Bulgarian). Konsulov, A., L. Kamburska. Chesapeake Sei, 8, 259-264. Bogdanova, D„ 1997. Sensitivity to anthropogenic factors of A. Konsulov. 1993. On the distribution of the plankton fauna adjacent to the Bulgarian the new Ctenophora species M nem ia coast of the Black Sea.-In: NATO ASI M ccradyi in the Black Sea along the Series, 2/27, 95-104. Malashev, V. I., Bulgarian coastline in the summer of Archipov, A. G. 1992. The Ctenophore 1990.-In: Comptes rendus de l’Academie Mnemiopsis leidyi in the West part of the bulgare des Sciences, no 46, 3, 71-74. Black Sea. Hydrobiology Jurn. IBSS, 28 / 1, Deason, E. and Smayda, T. J. 34-39. Nelson, T. C. 1925. On the 1982. Ctenophore-zooplankton-phytoplankton occurrence and food habits of ctenophores interactions in Narragansett Bay, Rhode in the New Jersey inland coastal waters.-In: Island, USA during 1972-1977.-In: Biol. Bull, 48 : 92-111. Prodanov, K. et al. J. Plankton Res, 4, 203-217. Fraser, H. F. 1997. Environmental management of fish 1962. The rople of Ctenophores and salps resources in the Black Sea and their rational in zooplankton production and standing cxploitation.-In: FAOrStudies and reviews, crop. Rapp. P-v. Reun.-In: Cons. perm. int. ?68. Swanberg N. 1970. The feeding Explor, Mcr, 153, 121-123. behavior of Beroe ovata.- In: Marine biology, GESAMP. 1997. Opportunistic settlers and 2 4 , 69-76. Vinogradov, M, E, et al. the problem of the ctenophore Mnemiopsis 1989. Ctenophore Mnemiopsis leidyi leidyi invasion in the Black Sea.-In: Reports (A. Agassiz) (Ctenophora: Lobata)-New and studies, ?58. Greeve, W. 1970. settlers in the Black Sea.-In: Oceanology, Cultivation experiments on North Sea Institute of Oceanology, 29 , 293-299, ctenophores. Helgoländer Moskva. Vinogradov, M. E., et al. Wiss. Meersunters, 20: 304-317. 1992. The Black Sea ecosystem.-Institute of Konsulov, A. 1989. One more New-comer. Oceanology, 5-109, Moskva. Zaitzev Yu. P, A New Species in the Black Sea-Dangerous V, Mamaev. 1997. Biological diversity in or Harmless for Ecology,-Morski Svjat 2 , 8. the Black Sea.-A study of change and Konsulov, A. 1991. Investigation on decline, GEF, Black Sea Environmental Biology, Ecology and the Meaning of the series, vol. 3. Zooplankton in the Black Sea in Front of - 198- EKOJiori/iHHa o6ycjiOBeHocT 3a HaBJii/i3aHeTo Ha HOBaTa KTeHO(f>opa (Beroe ovata) b HepHo Mope

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ripe3 nocjiegHHTe ABaaeceT toahhh b Beroe h HAeHTHcJmimpaH o t n a c k h t o Beroe pe3yjiTaT Ha noBHineHaTa eyxpo^HKayHii ovata. T o 3H x h iu h h k He e ctoömaBaH a o - h aHTponoreHHO B-b3fleiicTBHe HepHOMOp- cera 3a 4>ayHaTa Ha öacewHa. EcTecTBeHO- CKHHT SaceHH ce HBHBa ÖAaronpHHTeH 3a TO HaBAH3aHe Ha Beroe ovata b H cp H O Mope TpañHOTo ycTaHOBHBane Ha MHoro npH- HanpaBH H3AnuiHa HaMecaTa Ha HOBexa. IHBJIIIH. MaCOBOTO p33BHTHe Ha HHKOH OT HacToamaTa nyÓAHKanna ripcACTaBa oc- Tax BOflH AO ApaCTHHHH npOMCHH B 6mO- HOBHaTa HpHHHHa 3a HaBAH33HeTO Ha HO­ pa3HOo6pa3Hexo Ha n a aHKTOHHaTa <[>ayHa. BaTa 3a HepHO Mope KTeHO$opa Beroe ToBa ce oTHaca H3KAiomiTejiHo 3a npeac- ovata, a h m c h h o BHcoxaTa h h c a c h o c t Ha TaBHTeAHTe OT KAac C tenophora. 3a nep- M. leidyi, k o a t o e ocHOBHa xpaHa Ha h o - HOMopcKaTa iuiaHKTOHHa 4>ayna flo 1997r. b h a b m a- ToBa h h a a s a ocHOBaHHe Aa npii- ca H3BecTHn Aaa npeACTaBHxeAa Ha to3h eMCM, ne ecTecTBeHOTo HäBAH3aHe Ha h o - KAac - h Mnemiopsis b h a b h a b HepHo Mope e Tpo(})HHHo oöyc- leidyi. C n o p e g p e a tm a aBTopH MacoBOTO AOBCHO. pa3BHTHe Ha M. leidyi c a c a 1986 r, AOBe- Ho axo HOBaTa KTeHo^opa ce pa3Bne Ae AO HaMaAHBane na eKcriAoaTaitHOHHua MaCOBO, eAHMHHHpafiKH eAHa OT npHHHHH- 3anac Ha pHÔHTe h 6Hopa3Hoo6pa3neTO na Te 3a noBHiiicHa eyTpo4>HOCT-Mneijiippjiï 30onAaHKTOHa. GESAMP H3pa6 oTBa CTpa- leidyi, TOBa 6 h m o t a o ga AOBege a o h o b h TerHA 3a orpaHHnaBaHe pa3BHTHeTO h b ApaCTHHHH npOMCHH B UepHOMOpCK3Ta HepHO Mope. Eaho o t npeAAoaceHHHTa e eKocHCTeMa, ra ii Kaxo MacoBOTO pa3BttTHe 3a 0HOAOrHHeH KOHTpOA HpC3 HHTpOAyUH- Ha KxeHO<]>opHTe BHAOH3MeHH CTpyKTypa- pane Ha hchh xhiahhk ot pOA Beroe, a Ta AOpH Ha CTaÖHAHH ÖHOAOrHHHH CbOÖ- HMeHHO Beroe ovata, KoeTO hm3 k a k to npe- mecTBa. OcTaBa o t k p h t B t n p o c b T a s a h AHMCTsa, T axa h HeAOCTaT-bim. Beroe ovata m e ce ycTaHOBH Tpaïmo, Koti n p e3 oKTOMBpH 1997r. b pañoHa Ha me ôtA e HeÊHHHT x h ia h h k h Kora m e c e IUaèna 6e o t k p h t h o b npeACTaBHTen Ha nO H B H ? KAac Ctenophora, npHHaAAejKam k i m p o a

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