此物種詳細資訊 Black Sea, Turkey
來源： GESAMP, 1997
M. leidyi was first collected in the Black Sea in 1982 (Zaika V.E. and N.G.Sergeeva. 1990 in GESAMP, 1997). Before its introduction into the Black Sea, there was only a single species of ctenophore - Pleurobrachia pileus. (Mordukhai-Boltovskoi F.D. Ed., 1969. in GESAMP, 1997.
Development of the ctenophore Mnemiopsis leidyi population in the whole water area of the Black Sea started in 1988, reaching large abundance and biomass values in some years (1989-1990 and 1994-1995) (Vinogradov et al. 1989, 1992; Shiganova, 1997, 1998; Shiganova et al. 2001a). The main factors affecting the abundance of M. leidyi in the Black Sea include the environmental temperature (mostly winter temperature) and concentration of zooplankton - its main food (Shiganova, 1997, 1998; Shiganova et al. 2001a). Cold winters (1992-1993) sharply decreased its population in spring. A cold winter is usually followed by a relatively warm summer with a moderate temperature of the sea surface layer. Therefore low abundance of M. leidyi in spring corresponds with low abundance in summer. High water temperature in summer favour active reproduction of M. leidyi and rapid growth of its population. We observed warmings in 1999-2001 and high population size of M. leidyi before seasonal development of B.ovata. This was particularly pronounced in 2001 both in winter and summer (Dumont and Shiganova).
Analysis of seasonal dynamics of M. leidyi in the Black Sea and in other seas of the Mediterranean basin indicates similarities in the timing of maximum abundance and biomass, in spite of some differences in the initiation and duration of reproduction. A peak biomass and density occurred in 1989 in the Black and Azov Seas and in 1990 in the other seas (Dumont and Shiganova).
The Black Sea is the largest semi closed basin in the World, connected via the Bosporous Strait with the Sea of Marmara and via the Kerch Strait with the brackish Sea of Azov. Because of the restricted water exchange, waters below the permanent halocline at 60-200 m depth are anoxic (87% of the sea volume). The Cold Intermediate layer with temperature 6 8oC occurs between the permanent halocline and the seasonal thermocline in warm seasons. In this layer, the oxycline is the main factor determining the lower boundary of the planktonic community. The surface waters of the Black Sea are typical of temperate estuaries. This surface aerated zone, which includes the upper mixed layer, is above the seasonal thermocline at 15 25 m depth. Salinity is low at the surface (average 18‰) due to discharge of great rivers in the northwest, and 21.9 to 22.3 at depth. The surface waters are warmed to 24 27°C in summer, and cooled to 2-8°C and sometimes 0-0.5°C in shallow north-western area in winter. In winter, the seasonal thermocline breaks down, and the isothermal layer extends from the surface to 70-80 m (Dumont and Shiganova).
生態系統變化: Mnemiopsis leidyi causes negative impacts right through the foodchain of the areas it has invaded. The M. leidyi invasion negatively affected the ecosystems of the Black Sea and the Sea of Azov. The zooplankton, ichthyoplankton and zooplanktivorous fish stocks all underwent profound changes. Cascading effect occurred at the higher trophic levels, from a decreasing zooplankton stock to collapsing planktivorous fish to vanishing predatory fish and dolphins Similar effects occurred at lower trophic levels: from a decrease in zooplankton stock to an increase in phytoplankton, released from zooplankton grazing pressure. The majority of these effects were top-down, but a few were also bottom-up. Similar effects, but less pronounced, were recorded in the Sea of Marmara (Dumont and Shiganova).
最後修改 ： 30/05/2005 10:39:15 a.m.