Ammonium and nitrate uptake by Laminaria saccharina and Nereocystis luetkeana originating from a salmon sea cage farm

Abstract

In the laboratory, ammonium and nitrate uptakes were measured for juvenile Laminaria saccharina (L.) Lamour. and Nereocystis luetkeana (Mert.) Post. et Rupr. originating from a salmon sea cage farm in northwestern British Columbia, Canada. The effect of various concentrations of NH4+ and NO3-, which are typical of salmon farming environments, on uptakes values were examined. Both L. saccharina and Nereocystis revealed simultaneous uptake of NH4+ and NO3- when both NH4+ and NO3- were present in the medium. During a 3-h incubation, mean uptake rates of NH4+ and NO3- by L. saccharina ranged from 6.0–8.9 and 4.6–10.6 μmol gdw-1 h-1, respectively, and by Nereocystis, they ranged from 6.6–9.3 μmol gdw-1 h-1 and 6.1–17.0 μmol gdw-1 h-1, respectively. The highest uptake rates (14.8 μmol NH4+ gdw-1 h-1by L. saccharina and 27.2 μmol NO3- gdw-1 h-1 by Nereocystis) occurred at the highest concentration (40 μM NH4+ plus 30 μM NO3-) during a 1 h incubation. Nitrate uptake by both L. saccharina and Nereocystis increased linearly up to the highest nitrate level tested (30 μM), whereas uptake rates of ammonium were stable beyond 10 μM NH4+ to reach approximately 10 and 13 μmol gdw-1 h-1, respectively, for L. saccharina and Nereocystis. Unlike L. saccharina, Nereocystis showed a significant preference for NO3- when more than 20 μM NO3- was present in the medium ( p <0.05). Both L. saccharina and Nereocystis would be suitable for integrated cultivation of salmon/kelp.