Radiocesium in aquatic invertebrates from Dovrefjell, Norway, 1986 to 1989, after the Chernobyl Fall-out

Abstract Following the fall-out in 1986 from Chernobyl, the activity of 137 Cs was measured in invertebrates sampled in streams and temporary pools at 930 m above sea level at Dovrefjell, Norway (62° 17′N, 09° 59′E). Species with different feeding habits were selected, predators (e.g. Trichoptera, gen. Rhyacophila ), shredders (e.g. Trichoptera, gen. Halesus ), collectors/filterers (e.g. Trichoptera, gen. Polycentropus ) and plankton feeders (e.g. Cladocera, Daphnia and Anostraca, gen. Branchinecta ). Samples were preserved in 96% ethanol and were weighed to be between 0·05 and 2 g (mostly ∼0·7 g ). A sample thus consisted of many individuals. The 1986 radiocesium values vary considerably between and within species, and may reflect a patchy fall-out. The 1987, 1988 and 1989 data are much more consistent and are significantly lower than the 1986 values. The invertebrate predators have low radiocesium values and these showed a rapid decrease, whereas species eating dead or living plant material have measurable amounts of radiocesium in all the years. The data from 1987 and 1988 are fairly similar, but the 1989 data deviate from the previous two years. This difference may be caused by changes in deposition or transport of radiocesium in plants and soil.