Report of the Joint CIESM/ICES Workshop on Mnemiopsis Science (JWMS) (contribution of Lies Vansteenbrugge)

The ICES/CIESM Joint Workshop on Mnemiopsis Science (JWMS) chaired by Sophie Pitois (UK) and Tamara Shiganova (Russia), met in A Coruña, Spain from 18 to 20 September 2014. Scientists affiliated with the International Council for the Exploration of the Sea (ICES) and the Mediterranean Science Commission (CIESM) participated in the Joint Workshop to discuss the latest advances regarding the biogeography, ecology, impact and economic aspects of the invasive ctenophore Mnemiopsis leidyi and its Beroe predators (both native and invasive). The JWMS was attended by 20 scientists from 14 countries. The main objective of the workshop was to provide a forum for scientists to present and discuss the results of ongoing relevant research projects in the North Atlantic and Mediterranean. The 13 presentations stimulated wide ranging discussions relevant to Mnemiopsis science.
Highlights
• The latest knowledge regarding the biogeography and ecology of Mnemiopsis
leidyi and of its Beroe predators were reviewed, as well as the spatialand
temporal occurrences across the ICES-CIESM sea basins. It was recognized
that Beroe spp. are not the only predators of M. leidyi and that the
various interactions of M. leidyi with the different components of the ecosystem,
as well as mechanisms involved, are too complex to be comprehensively
understood.
• Mnemiopsis leidyi is most likely exhibiting source-sink population dynamics
within its European range.
• European seas are warming at present, and temperature is likely to affect
the timing and distribution of both M. leidyi and Beroe spp. in those areas.
However, the link with temperature was questioned, and the hypothesis
was put forward, that food web pertubations from overfishing combined
with eutrophication in coastal areas and major influx of invasive aliens,
have permitted the establishment of Mnemiopsis propagules in some areas.
• M. leidyi has a wide environmental tolerance and phenotypic variability.
Environmental conditions influence the development of M. leidyi, however
it can establish in highly contrasting ecosystems. Its morphological features,
growth rate, metabolism, size of maturity, fecundity differ according
to environmental conditions particularly considering salinity, temperature,
productivity and prey concentration.
• Modelling tools, based on experimental physiological knowledge, help to
predict/understand the aforementioned processes and interactions. Several
approaches were presented and discussed.
• At the same time it was acknowledged that there is not enough information
on M. leidyi occurrence, seasonal and interannual variability in some areas, particularly in northern Europe and specific areas of the Mediterranean
Sea. Improved monitoring and more comprehensive coverage of
investigated areas are therefore deemed necessary, in particular field investigations of overwintering areas are needed.
• A key parameter to understand population dynamics is the winter biology
of M. leidyi. Therefore more research effort should be devoted (i) to understand
the low temperature/low food environmental interactions with M. leidyi and its survival under these conditions; (ii) to identify sites of overwintering
populations.
• Citizen science may provide a valuable tool to improve our knowledge on
poorly monitored areas, and should be encouraged.