Culture, yield and bioremediation potential of Palmaria palmata (Linnaeus) Weber & Mohr and Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl & G.W. Saunders adjacent to fish farm cages in northwest Scotland

Growth of seaweeds in the vicinity of fish farm cages in northwest Scotland was investigated as a means of extracting, from the surrounding water, nutrients added via fish feed and excretory products. Enhanced growth and yields of Palmaria palmata and Saccharina latissima cultures were found when grown adjacent to fish farm cages. Growth rates in summer for P. palmata and S. latissima were enhanced by up to 48% and 61%, respectively, and biomass yields over a growth season were enhanced by 63% and 27%, respectively. The nitrogen content of the macroalgae grown close to the fish cages was greater than for those grown at reference sites away from the cages. Extrapolation show that under optimal conditions, a hectare of P. palmata could yield up to 180 tonnes wet weight per annum and a hectare of S. latissima 220 tonnes wet weight per annum. Conservative estimates of yields show that P. palmata could be expected to remove up to 12% and S. latissima 5% of the waste nitrogen released during the growth of 500 tonnes of salmon in the sea over 2 years. The practicalities and logistics of culturing macroalgae near fish cages are considered and, because of the wide distribution of nitrogen emanating from fish culture and the need to optimise growth conditions for cultured macroalgae, it is recommended that macroalgal culture for bioremediation should be considered at wider geographical scales i.e., bay wide at least. (C) 2012 Elsevier B.V. All rights reserved.