Bivalves at Work: Quantifying Nutrient Removal Services in UK Coastal Waters

Nutrient loading from agriculture, urban discharge, and industrial effluents contributes to eutrophication, a critical environmental challenge impacting water quality. This research evaluated the role of bivalves in nutrient removal as a bioremediation tool within UK aquatic systems, focusing on mussels Mytilus edulis , Pacific oysters Magallana gigas , (formerly Crassostrea gigas ), native oysters Ostrea edulis , and Manila clams Ruditapes philippinarum . The monetary value of these services was estimated and compared to costs of alternative mitigation methods (e.g. removal during water treatment) and potential integration into nutrient credit trading schemes was explored.The effectiveness of bivalves in nitrogen and carbon removal ranged from 126 to 286 tonnes of N, with an estimate of 1762 tonnes of C removed, despite production decline since 2015 in the UK. In 2019, mussels accounted for 92.2% of nitrogen and 83.5% of carbon removal due to higher yields, with Scotland and England leading in aquaculture production. However, increased Pacific oyster cultivation offers potential for higher nutrient removal, especially in eutrophic and nutrient-rich areas. The potential annual value of nitrogen removal by bivalves ranged from £33,000 to over £314 million, depending on estimated harvest and type of alternative strategies used for the estimate.Bivalve bioremediation offers significant promise as part of holistic nutrient management strategies, complementing other nature-based solutions. Expansion of UK bivalve aquaculture could enhance ecosystem services, support water quality improvements, and provide economic benefits, encouraging further inclusion of bivalves in nutrient management policies. Future work needs to focus on regional case studies and establishing a framework for including bivalve bioremediation in water management schemes while ensuring public acceptance and safety.