Blooms of the invasive ctenophore, Mnemiopsis leidyi, in the Spanish and Israeli coasts (Mediterranean Sea) in 2009

Third International Jellyfish Blooms Symposium, 13-16 July 2010, Mar de Plata, Argentina

In this study we report the first observation of large swarms of the comb jelly Mnemiopsis leidyi along the Spanish coast of the NW Mediterranean Sea in the same time-period when the species was very abundant along the eastern Mediterranean coast of Israel. On the Spanish coast, large numbers of M. leidyi were first reported in July 2009 and occurred throughout the summer (last report 26 September 2009) whereas the swarms were first observed in January 2009 along the Israeli coast. We conducted molecular confirmation of the ctenophores identity to avoid any misidentification. The high concentrations of M. leidyi along the Spanish, Italian (separate study) and Israeli coasts, suggest this species is established in the Mediterranean Sea. We compare the conditions in the Mediterranean Sea which are very different (warm temperatures, high salinities and low productivity) from those in the northern habitats invaded by M. leidyi, and conclude that this ctenophore is unlikely to be constrained by physical conditions in the Mediterranean Sea. On the other hand, we propose that a variety of gelatinous species that could be potential predators and competitors of M. leidyi may constrain its success. We also report an unusual pattern of jellyfish abundances during the period that M. leidyi was very abundant

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