EVALUATING THE CO-CULTIVATION POTENTIAL OF PALMARIA PALMATA AND BIVALVES IN HERRING PRODUCTION PROCESS WATER

Sammanfattning

High nutrient emissions from food production and processing highlight the need for circular approaches that enable recovery of otherwise wasted recourses. Process water from the herring production industry (HPPW) is rich in dissolved and particulate nutrients but is being treated as waste. This study investigated the response of European Flat Oysters (Ostrea edulis) and Blue Mussels (Mytilus edulis) in HPPW and evaluated the co-cultivation potential of the red seaweed Palmaria palmata with these bivalves in HPPW in winter conditions. To start, a screening of bivalves in HPPW was conducted, where bivalve activity was visually assessed via valve opening behaviour. Bivalves showed reduced activity at HPPW concentrations above 40 µM, indicating sensitivity above these levels to the process water. Based on these results, a six-week experiment compared monocultures and co-cultivation with O. edulis and P. palmatain HPPW and seawater (SW) controls. Seaweed responses were measured through growth, tissue nitrogen content, pigments, and nutrient concentrations in the water. The results showed that HPPW increased tissue nitrogen and pigment content in P. palmata but had no significant effect on growth. Co-cultivation had limited overall effects, although an interaction between water type and cultivation was observed for phycobiliproteins in P. palmata. Seaweeds reduced dissolved inorganic nutrients, while bivalves contributed to ammonium release, indicating complementary nutrient pathways. Overall, HPPW showed potential as a nutrient source for seaweed cultivation, while co-cultivation with bivalves indicated possible benefits for nutrient removal and bioremediation. However, successful integration of bivalves into HPPW based co-cultivation systems will require careful consideration of water quality characteristics and environmental conditions.