INTEGRERAD MULTITROFISK AKVAKULTUR – EN LÖSNING FÖR ÖSTERSJÖN? Samodling av musslor och tång

Sammanfattning

Eutrophication in the Baltic Sea remains a serious environmental problem despite extensive land-based mitigation measures. This has increased interest in internal measures that actively remove nutrients from the marine environment. Integrated Multi-Trophic Aquaculture (IMTA), in which organisms from different trophic levels are co-cultivated to create circular and resource-efficient systems, has been proposed as one such measure. The aim of this study was to analyse and synthesize existing research on the environmental effects of cocultivating blue mussels (Mytilus edulis) and seaweeds (primarily Saccharina latissima) through a literature review. The study focused on nutrient dynamics, water quality, and local ecological effects, with particular emphasis on the potential application of such a system in the brackish waters of the Baltic Sea. The results show that mussel farming generally accounts for the largest nutrient removal per unit area, while seaweed contributes less overall but plays an important role through the uptake of dissolved nutrients released by mussel metabolism. Several studies indicate that seaweed can function as a compensatory component by recapturing some of the nutrients that would otherwise be returned to the water column. Mussel farming also contributes to reducing chlorophyll concentrations and improved water clarity through the filtration of phytoplankton. Furthermore, co-cultivation demonstrates positive synergies, including enhanced seaweed growth, improved light conditions, and more efficient nutrient utilization. The findings therefore suggest that co-cultivation can contribute to improved water quality and increased nutrient retention compared with mussel monoculture alone. However, the effectiveness of this system is constrained by factors such as low salinity, seasonal variability, and local hydrodynamic conditions. Co-cultivation of mussels and seaweeds should therefore not be regarded as a standalone solution to the Baltic Sea’s eutrophication problem, but rather as a valuable complement to other management measures in suitable coastal environments. Further research is needed, particularly regarding alternative species, large-scale implementation of IMTA-systems, and their long-term effects under the specific environmental conditions of the Baltic Sea.