Mnemiopsis leidyiThe American comb jelly Mnemiopsis leidyi was introduced via ballast waters in the Black Sea during the 1980s. This voracious comb jelly consumes everything from zooplankton to fish larvae, ingesting up to ten times its body weight per day. Due to the lack of natural predators in the Black Sea, the population of M. leidyi grew explosively, devastating the ecosystem within a few years, and leading to the collapse of the anchovy fishery. Mnemiopsis leidyi further spread into the Mediterranean Sea, where high densities of comb jellies disrupted the cooling system of industrial plants.

Since 2006, M. leidyi has been found in the 2 seas region, but only at low densities thus far. As this is a highly productive and commercially important area, it is necessary to carry out a detailed study to fill the knowledge gaps related to the potential impact of M. leidyi in this region in order to avoid a similar ecological and economic disaster as observed in the Black Sea.

The first knowledge gap concerns the identification and distribution of M. leidyi in the 2 seas region. In the past, erroneous characterization has led to misidentifications of this comb jelly. In the MEMO project, a genetic tool will be developed to facilitate identification. A standardized sampling protocol will be set up to collect and preserve comb jellies for morphological and genetic characterization. Samples will be gathered on several surveys and on a joint dedicated cruise. Appropriate methods will be applied to investigate the spatio-temporal distribution and spread of M. leidyi along the coasts and harbors of the 2 seas region. All these data will lead to the development of distribution maps and habitat models.

Invasive species are typically opportunistic and can withstand extreme conditions. A second problem that MEMO will address is our lack of knowledge and understanding of the physiology and feeding behavior of M. leidyi.

Questions to be answered within the MEMO project concern growth, reproduction and feeding activities of M. leidyi in relation to prey preference, prey availability and presence of potential predators. Data on predators and food sources (other gelatinous plankton, zooplankton and phytoplankton) will be gathered concurrently during the same sampling surveys (Activity 1).

In Activity 2, the ecological preferences of M. leidyi will be defined via lab experiments and the results used to develop mathematical models, in close cooperation between the different partners.

In Activity 3, mathematical models on distribution, physiology, growth, feeding and predation will be coupled to an ecosystem model. Additionally, a socio-economic study and model will be conducted and developed. Both models will contribute to the assessment of the potential impacts of M. leidyi in the 2 seas region in relation to changes in the environment.

The project will provide tools for various stakeholders (e.g., institutions, local industries and regional councils) to estimate the potential impact of M. leidyi on fisheries, recreational activities and other industries. The tools will be applied to three specific case studies in the 2 seas region. The MEMO project is an opportunity to work together in a cross border approach on the invasive species M. leidyi. Specific workshops and continuous communication with the stakeholders at the regional and international level will constitute a major activity. By sharing knowledge and expertise within the 2 seas region, the project will contribute to a proactive approach, giving policy-makers the opportunity to anticipate the ecological and economic problems related to this invasive comb jelly using scientifically-based mitigation measures.

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