The impact of a mussel farm on water transparency in the Kiel Fjord

Abstract

Mussel farming is a highly discussed opportunity for inner coastal management measures to counteract the eutrophication of the Baltic Sea. There is currently a lack of detailed feasibility analyses for mussel aquaculture in German coastal waters. In 2010, a blue mussel (Mytilus edulis) farm began operating in the Kiel Fjord. In this study, we present an analysis combining measurements from this farm with a 3D-circulation and ecosystem model. We show that the mussel farm in the Kiel Fjord is incapable of producing harvests as large as farms in Swedish coastal waters. We assess and formulate the impact of the mussel farm on water transparency and calculate the attenuation coefficient and the Secchi depth from model data. Although water quality improvements are low due to the size of the farm, our results show that the area of increased water transparency is not limited to the farm area and even reaches the shoreline. We also examine the economic feasibility of the mussel farm and calculate the size of farm area, necessary to remove 10% of the riverine nutrient loads into the Kiel Fjord. We conclude that mussel farming can be a suitable supporting measure to improve water quality by removing nutrients and increasing water transparency in Kiel Fjord.