Accumulation of lead (Pb) in brown trout (Salmo trutta) from a lake downstream a former shooting range

Abstract

An environmental survey was performed in Lake Kyrtjønn, a small lake within an abandoned shooting range in the south of Norway. In Lake Kyrtjønn the total water concentrations of Pb (14 µg/L), Cu (6.1 µg/L) and Sb (1.3 µg/L) were elevated compared to the nearby reference Lake Stitjønn, where the total concentrations of Pb, Cu and Sb were 0.76, 1.8 and 0.12 µg/L, respectively. Brown trout (Salmo trutta) from Lake Kyrtjønn had very high levels of Pb in bone (104 mg/kg w.w.), kidney (161 mg/kg w.w.) and the gills (137 mg/kg d.w), and a strong inhibition of the ALA-D enzyme activity were observed in the blood (24% of control). Dry fertilized brown trout eggs were placed in the small outlet streams from Lake Kyrtjønn and the reference lake for 6 months, and the concentrations of Pb and Cu in eggs from the Lake Kyrtjønn stream were significantly higher than in eggs from the reference. More than 90% of Pb accumulated in the egg shell, whereas more than 80% of the Cu and Zn accumulated in the egg interior. Pb in the lake sediments was elevated in the upper 2–5 cm layer (410–2700 mg/kg d.w), and was predominantly associated with redox sensitive fractions (e.g., organic materials, hydroxides) indicating low potential mobility and bioavailability of the deposited Pb. Only minor amounts of Cu and Sb were deposited in the sediments. The present work showed that the adult brown trout, as well as fertilized eggs and alevins, may be subjected to increased stress due to chronic exposure to Pb, whereas exposure to Cu, Zn and Sb were of less importance.