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

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 (1 yr). The results showed that it was possible to obtain a high area specific biomass of 60 t WW ha(-1) eqvivalent to a nitrogen and phosphorus removal of 0.6-0.9 and 0.03-0.04 t ha(-1)yr, 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(-1)N making mitigation mussel production a cost-efficient measure compared to the most expensive land-based measures.