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POST-INVASION ECOLOGICAL IMPACT OF THE ATLANTIC CTENOPHORE
MNEMIOPSIS LEIDYI AGASSIZ, 1865 ON THE ZOOPLANKTON FROM THE
ROMANIAN BLACK SEA WATERS


Adriana Petran, Maria Moldoveanu 
Romanian Marine Research Institute Constanta

Abstract
The study presents the evolution of the zooplankton communities from
the Romanian Black Sea waters in the period 1989-1993 after the 
outburst of the new immigrant in the pelagic zone of the Black Sea-
the predator lobate ctenophore Mnemiopsis leidyi. The paper, based 
on the 480 zooplanktonic samples processed, evinces that, after the
Mnemiopsis invasion, the structure of the zooplanktonic communities
were significantly transformed. Especially during the summer, a 
severe reduction of populations for the most of the groups with
trophic value has registered, the biomasses of some species decreasing
3-5 times or more. Even the species with intensive growth during the
previous years (1980-1987), such as Acartia clausi and Pleopis 
polyphemoides, have had now a very low quatitative level.

Key words: Black Sea, zooplankton, Mnemiopsis leidyi