Impact of Atlantic salmon cage culture on sediment chemistry in Mjoifjordur, Iceland

Impact of Atlantic salmon (Salmo salar) cage culture in Mjoifjordur, Eastern Iceland on the chemistry of the sediment was investigated. Sediment samples were collected using a Shipek grab in December 2003. A core sub-sample was taken from each grab for analyzing total organic matter, total organic carbon, total nitrogen and phosphorus in different depths from three stations at various distances from the cage. These parameters were analyzed in the top layer of additional four stations. The results showed significant increase in all analyzed parameters in station 1, at 5m from the cage (p<0.05). The difference between reference station (600 m from the cage) and station 2 at 95 m to the cage was insignificant (p>0.05), indicating localized impact of cage farming to the vicinity of cage. The analyzed parameters in various depth did not show significant differences (p>0.05). The value of analyzed parameters in the perimeter of the cage and their differences with reference stations showed small magnitude and localized impact on the chemistry of sediment. It might be due to deep water and moderate velocity of water current in this fjord. The magnitude of impact may differ during the summer season when biomass and feeding rate would be at the maximum level.