Persistent organic pollutants and trace metals in sediments close to Scottish marine fish farms

The global demand for aquatic food products is increasing and the aquaculture industry is expanding as it strives to meet this increasing demand. There are concerns about the environmental impact of aquaculture to the seabed close to fish-farm cages, including potential effects from persistent organic pollutants and trace metals, which may come from the feed or anti-foulants on the cages. To determine if this could be a problem in Scotland, three main aquaculture areas were examined; Western Isles, North-West Coast of Scotland and the Shetland Isles. Samples of sediment were collected from various sea lochs in these areas in 2005 and 2006 and concentrations of persistent organic pollutants (polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs)) and trace metals (copper (Cu) and zinc (Zn)) were determined. Concentrations of PCBs were below the EAC (environmental assessment criteria) for all bar one congener in one sample, and below the BAC (background assessment concentration) for most. PBDE concentrations in the sea lochs are comparable with those found at remote sites around Scotland and comparable with the lower end of concentrations found in the more industrialised Firth of Clyde. Although slightly elevated Cu and Zn concentrations were measured in sediments from <330 m from some farms, concentrations in sediments outwith 25 m from any farm are below those that cause benthic effects. Only the farms in Loch Shell, Loch Greshornish and Loch Kishorn had concentrations for Cu and Zn which might cause adverse affects in the environment, and all of these samples were from within 25 m of the cages. Therefore it was concluded that any impact on the environment from organic pollutants or trace metals is of a local nature. (C) 2011 Elsevier B.V. All rights reserved.