Mnemiopsis leidyi in the Baltic Sea region: Origin, transport and seasonality

The comb jelly Mnemiopsis leidyi, native to the east coast of America, has a long invasion history in European waters. Its first sighting dates back to the early 1980s from the Black Sea (Purcell et al., 2001). Mnemiopsis leidyi invaded the Black Sea in the 1980s with cascading effects on several ecosystem levels including commercial fisheries (Kideys, 2002). This native to the east coasts of America triggered large public and scientific attention as a result of this invasion and its ecological and economic impacts. In 2005, when M. leidyi was sighted in Northern Europe for the first time (Faasse and Bayha, 2006), similar consequences were feared. M. leidyi introduced to northern Europe around originates from a different North American sub-population. Hence, microsatellite markers revealed that the south European M. leidyi population stems from the southeast coast of the US, namely the Gulf of Mexico, while the north European population could be traced back to the northeast coast (Reusch et al., 2010). To date it is unknown if pre-adaptation in its native range has set the invasion corridor of M. leidyi in European waters. However, so far it has been shown that the south European M. leidyi population cannot tolerate water temperatures <4⁰C (Shiganova et al., 2001), while the northern population has been shown to overwinter under the ice in its native range (Costello et al., 2006). Due to difficulties of morphological identification of its larval stages, there has been some ambiguity about M. leidyi's distribution range in northern Europe, especially the Baltic Sea. Here we synthesize data on the range expansion of M. leidyi in the entire Baltic Sea region, including its larval stages as confirmed by DNA analyses (Jaspers et al., 2013) and we present preliminary results of a drift model to predict possible seeding areas.