Abstract: Sulphur emissions from Russian Kola Peninsula smelters are known to cause surface water acidification in the border areas between Norway and Russia. The sulphur deposition is also high in the eastern part of Finnish Lapland. In 1990, a monitoring programme was started to survey the effects of acid deposition on sensitive fish populations in north-eastern Finnish Lapland. Altogether 103 sites in three areas were electrofished and autumn water samples were taken. Besides the brown trout (Salmo trutta), special attention was paid to the occurrence of minnow (Phoxinus phoxinus) since it is a common species in small waters and is highly sensitive to acidification. During the first three years of monitoring no signs of acidification were recorded. The alkalinity values of brooks generally exceeded 0.1 mmol/1. Brown trout, minnow and burbot (Lota lota) were caught frequently in the study sites. Later the study was focused on the uninhabited Vätsäri area which is receiving the highest sulphur deposition in Finnish Lapland. The alkalinity values of the sampled brooks were in most cases below 0.05 mmol/1, indicating a decreased buffer capacity. However, the electrofishing of the brooks showed no acid-induced damage. The lowest alkalinity values were detected from a group of small upland ponds. In four such ponds the alkalinity was zero or negative. No minnows were caught from these four ponds apart from one, where the minnows were exceptionally large. The results show that the waters near the eastern border of northern Finnish Lapland are threatened by acidification. No damage to fish populations subject to fishing was observed. The absence of minnows in some small waters is possibly the first sign of acid-induced fish population damage.

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   |texte=   Acid deposition from the Russian Kola Peninsula: Are sensitive fish populations in north-eastern Finnish Lapland affected?
}}