Heavy metals in seabed sediments beneath off-shore fish cages

The aquaculture industry has been steadily increasing worldwide in the last decade and currently there are more off-shore cages. Environmental impacts of off-shore cages have been focused on the effects of uneaten pellets and fish faeces on benthic assemblages. However, the release of heavy metals associated with aquaculture activities remains poorly studied. In the present study, the concentrations of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) on sediments beneath off-shore fish cages were analyzed. Two aquaculture leases were sampled in two locations, NE and SW of Tenerife (Canary Islands, NE Atlantic Ocean). Sediments from unaffected locations were sampled to determine if there were significant changes in heavy metals composition on sediments due to aquaculture activities. There were significant differences in Cd, Co, Cr, Cu, Ni, Pb and Zn at both areas, with the exception of Mn that was in high amount. The high content of Mn collected in samples from both areas could have a volcanic origin. The concentrations of heavy metals find out in sediments beneath offshore seabed cages do not present risk for environment. VIERAEA Vol. 45 367-380 Santa Cruz de Tenerife, octubre 2017 ISSN 0210-945X 368 HERNÁNDEZ-SÁNCHEZ et al.