Mussels as a tool for mitigation of nutrients in the marine environment

•We have assessed the potential of mussel production as mitigation tool.•The study is based on a full scale mussel farm optimized for nutrient removal.•Biological and economic parameters was monitored.•Mussel farming is a cost-effective mitigation measure.•Mussel farming can be used in addition to land-based mitigation measures. Long-line mussel farming has been proposed as a mitigation tool for removal of excess nutrients in eutrophic coastal waters. A full-scale mussel farm optimized for cost efficient nutrient removal was established in the eutrophic Skive Fjord, Denmark where biological and economic parameters related to nutrient removal was monitored throughout a full production cycle (1yr). The results showed that it was possible to obtain a high area specific biomass of 60tWWha−1eqvivalent to a nitrogen and phosphorus removal of 0.6–0.9 and 0.03–0.04tha−1yr, respectively. The analysis of the costs related to establishment, maintenance and harvest revealed that mussel production optimized for mitigation can be carried out at a lower cost compared to mussel production for (human) consumption. The costs for nutrient removal was 14.8€kg−1N making mitigation mussel production a cost-efficient measure compared to the most expensive land-based measures.