Trophic ecology of the Invasive Ctenophore Mnemiopsisleidyi A. Agassiz 1865 in the Western Baltic Sea.

Supervisor: Jamileh Javidpour (Univ. Southern  Denmark & Chinese Academy of Sciences)
Invasive species and their negative effect on native organisms is amongst the many pressures that humans place on marine ecosystems. The ctenophore MnemiopsisleidyiA. Agassiz 1865 is a prime example of an invasive species as they are known for having caused damage to fisheries and coastal ecosystems of several enclosed and semi-enclosed seas around Eurasia. M. leidyiare considered to be a voracious planktivorous feeder which undergoes a diet change as it transitions from a cydippid larvae to the lobate morphology of the adult. It was initially thought that this species was exclusively carnivorous but it is now well established that the cydippid larvae can feed on autotrophic and heterotrophic protists. However the importance of protists in the diet of adult M. leidyiis still up for debate. Previous studies have looked at the diet of M. leidyibut mainly through the scope of gut content. These studies give us valuable information for species with hard body parts but give little information on the consumption of natural microplankton assemblages, nor do they inform us on the assimilation of ingested prey. The current study is one of the first to investigate the trophic ecology of M. leidyithrough the scope of stable isotopes and fatty acids. M. leidyihave been reported in the Baltic Sea since 2006 where it rapidly colonised large areas of the basin. The current study took place in the Kiel Fjord, an extention of the Belt Sea which, with the Danish Straits, links the Baltic Sea to the North Sea. Feeding of M. leidyiwas investigated for microplankton, mesozooplankton, fish eggs and larvae and Aurelia auritaplanula. Differences in between M. leidyisize clases were also analysed.