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Ctenophora: Hungry Immigrants

Threat to fish stocks in the Baltic Sea, a predatory jellyfish could disrupt ecosystem. The Penilia species Mnemiopsis leidyi around 1980, sea surfaced suddenly in black, are freely propagated and triggered an almost 20-year ecological disaster. The Mnemiopsis in almost all oceans owed the conquest of their new Habitat of an around the world as a “stowaway” in water ballast tanks of ships. Due to the since 1970 in the Black Sea increasing salinity of sea water, as well as overfishing and marine pollution found Mnemiopsis not only ideal living conditions, but had also no natural predators. In the following years, the voracious immigrants developed a tremendous appetite for Zoo plankton, fish eggs and larvae of cancer. Around 1989 the Goo-predator biomass amounted to around 1 billion tons, while the number of valuable fish such as anchovy and sprat had fallen dramatically. Temporarily, scientists even considered one of the natural enemies of Mnemiopsis, which related to her, predatory melon jellyfish (Beroe ovata), to move into the Black Sea. These animals suck their prey themselves into and take between three and five hours to digest a Mnemiopsis.

The idea appeared too risky in light of various ecological disaster in the settlement of foreign organisms, such as when the Cane Toad in Australia or with Mongoose on the Hawaiian Islands. But Beroe ovata came from all alone. in 1997 the first copies of the melon jellyfish appeared, probably also introduced about ballast water pumped off. I could not believe it”, Tamara Shiganova rejoiced by the Shirov Institute of Oceanology in Moscow. It began a merciless hunting, predatory jellyfish against predatory jellyfish, which ended with the collapse of the defeated Mnemiopsis population. Scientists expect that Beroe ovata, sang after work in the course of time in the Black Sea and quietly die off and cause no damage to the ecosystem is. Samantha destruction arts of Beroe could be soon somewhere else. In 2006, Mnemiopsis leidyi first appeared in the On the Baltic Sea in the Bay of Kiel and since then quickly spreads.

In October 2007 she already had the Gdask Bay and Gulf of Finland the Finnish and Gulf of Bothnia. In the Baltic Sea it has seen off Mnemiopsis especially on the eggs of goby, Seestichling, cod and whiting. Still, experts assume that the newcomers are here not to rage as it was possible for them in the Black Sea. For a proliferation of it might be simply too cold the predatory jellyfish in the Baltic Sea, only in August, when water temperatures reach the 20 level, optimal conditions for the hungry immigrants. However, one must not underestimate Arts adaptation of Mnemiopsis. Successfully, manages the jellyfish actually on mild temperatures to overwinter in water temperatures of around nine degrees Celsius in the Baltic Sea. Ulrich Karlowski