Title: Impact of cage culture on sediment chemistry: A case study in Mjoifjordur

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 on 29.12.2003. A core sub-sample has taken from each grab for analyzing total organic matter, total organic carbon, total nitrogen and phosphorus in different depths of samples from three stations at various distances from the cage. These parameters were analyzed in the top layer of additional four stations. The results show a significant increase in all analyzed parameters in station 1, at 5 m 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, indicating localized impact of cage farming to the vicinity of cage (P<0.05). The analyzed parameters in various depth did not show a significant differences (P<0.05). The value of analyzed parameters in the perimeter of the cage and their differences with reference stations show 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.