Jonne Kotta1, Martyn Futter2, Ants Kaasik3, Kiran Liversage3, Merli Rätsep3, Francisco R Barboza4, Lena Bergström5, Per Bergström6, Ivo Bobsien4, Eliecer Díaz7, Kristjan Herkül3, Per R Jonsson8, Samuli Korpinen9, Patrik Kraufvelin7, Peter Krost10, Odd Lindahl11, Mats Lindegarth6, Maren Moltke Lyngsgaard12, Martina Mühl10, Antonia Nyström Sandman13, Helen Orav-Kotta3, Marina Orlova14, Henrik Skov15, Jouko Rissanen9, Andrius Šiaulys16, Aleksandar Vidakovic17, Elina Virtanen9. 1. Estonian Marine Institute, University of Tartu, Mäealuse 14, EE-12618 Tallinn, Estonia. Electronic address: jonne@sea.ee. 2. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Box 7050, SE-75007 Uppsala, Sweden. 3. Estonian Marine Institute, University of Tartu, Mäealuse 14, EE-12618 Tallinn, Estonia. 4. GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, DE-24105 Kiel, Germany. 5. Department of Aquatic Resources, Swedish University of Agricultural Sciences, Skolgatan 6, SE-74242 Öregrund, Sweden. 6. Department of Marine Sciences - Tjärnö Marine Laboratory, University of Gothenburg, Tjärnö, SE-45296 Strömstad, Sweden. 7. Novia University of Applied Sciences, Raseborgsvägen 9, 10600 Ekenäs, Finland. 8. Department of Marine Sciences - Tjärnö Marine Laboratory, University of Gothenburg, Tjärnö, SE-45296 Strömstad, Sweden; Environmental and Marine Biology, Åbo Akademi University, Finland. 9. Marine Research Centre, Finnish Environment Institute, FIN-00790 Helsinki, Finland. 10. Coastal Research and Management, Tiessenkai 12, D-24159 Kiel, Germany. 11. Musselfeed AB, Hallgrens väg 3, SE-47431 Ellös, Sweden. 12. Orbicon, Department for Nature and Environment, Jens Juuls vej 16, 8260 Viby J., Denmark. 13. AquaBiota Water Research, Löjtnantsgatan 25, SE-11550 Stockholm, Sweden. 14. Sankt-Petersburg Research Centre of Russian Academy of Science, University embankment 5, 199034 St.-Petersburg, Russia. 15. DHI, Agern Alle 5, 2970 Hørsholm, Denmark. 16. Marine Research Institute, Klaipeda University, Universiteto ave. 17, LT-92294 Klaipėda, Lithuania. 17. Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Box 7024, SE-75007 Uppsala, Sweden.
Abstract
Eutrophication is a serious threat to aquatic ecosystems globally with pronounced negative effects in the Baltic and other semi-enclosed estuaries and regional seas, where algal growth associated with excess nutrients causes widespread oxygen free "dead zones" and other threats to sustainability. Decades of policy initiatives to reduce external (land-based and atmospheric) nutrient loads have so far failed to control Baltic Sea eutrophication, which is compounded by significant internal release of legacy phosphorus (P) and biological nitrogen (N) fixation. Farming and harvesting of the native mussel species (Mytilus edulis/trossulus) is a promising internal measure for eutrophication control in the brackish Baltic Sea. Mussels from the more saline outer Baltic had higher N and P content than those from either the inner or central Baltic. Despite their relatively low nutrient content, harvesting farmed mussels from the central Baltic can be a cost-effective complement to land-based measures needed to reach eutrophication status targets and is an important contributor to circularity. Cost effectiveness of nutrient removal is more dependent on farm type than mussel nutrient content, suggesting the need for additional development of farm technology. Furthermore, current regulations are not sufficiently conducive to implementation of internal measures, and may constitute a bottleneck for reaching eutrophication status targets in the Baltic Sea and elsewhere.
Eutrophication is a serious threat to aquatic ecosystems globally with pronounced negative effects in the Baltic and other semi-enclosed estuaries and regional seas, where algal growth associated with excess nutrients causes widespread pan class="Chemical">oxygen free "dead zones" and other threats to sustainability. Decades of policy initiatives to reduce external (land-based and atmospheric) nutrient loads have so far failed to control Baltic Sea eutrophication, which is compounded by significant internal release of legacy pan class="Chemical">phosphorus (P) and biological nitrogen (N) fixation. Farming and harvesting of the native mussel species (Mytilus edulis/trossulus) is a promising internal measure for eutrophication control in the brackish Baltic Sea. Mussels from the more saline outer Baltic had higher N and P content than those from either the inner or central Baltic. Despite their relatively low nutrient content, harvesting farmed mussels from the central Baltic can be a cost-effective complement to land-based measures needed to reach eutrophication status targets and is an important contributor to circularity. Cost effectiveness of nutrient removal is more dependent on farm type than mussel nutrient content, suggesting the need for additional development of farm technology. Furthermore, current regulations are not sufficiently conducive to implementation of internal measures, and may constitute a bottleneck for reaching eutrophication status targets in the Baltic Sea and elsewhere.