Ecological-social-economic assessment of zebra-mussel cultivation scenarios for the Oder (Szczecin) Lagoon

Abstract

The Systems Approach Framework with an integrated Ecological-Social-Economic assessment was applied to address the issue of zebra mussel (Dreissena polymorpha) farming in the large Oder (Szczecin) Lagoon, southern Baltic Sea. Heavy eutrophication hampers the use of the lagoon and zebra mussel farming is considered as new use and potential measure to improve water quality. Three alternative scenarios were developed in interaction with local stakeholders: 1) the production of mussels as fresh feed and meal on a commercial basis seemed not profitable, because of a limited market for fresh mussels (zoos, aquaculture) and low prices for organic feed. 2) Mussel cultivation to improve transparency and attractiveness of bathing waters near beaches had only a limited potential (0.2 m improvement of Secchi depth). A higher mussel biomass would increase the risk of temporary hypoxia. 3) Mussels farms for improving the environmental status (according to EU Water Framework Directive) by supporting macrophyte restoration were considered as the most promising scenario. Our model simulations suggested that as soon as a compensation for nutrient removal is considered, all mussel farm scenarios could cover the costs. Experiments and literature confirm that the conditions for an environmental friendly farming approach in the lagoon are suitable. Steps towards and problems associated with an implementation, e.g. invasion of Dreissena bugensis (quagga mussel), are discussed. Each step of the Ecological-Social-Economic assessment and major lessons learnt are documented in detail. Altogether, the approach turned out to be very suitable for this issue.