ACID DEPOSITION FROM THE RUSSIAN KOLA-PENINSULA - ARE SENSITIVE FISH POPULATIONS IN NORTH-EASTERN FINNISH LAPLAND AFFECTED

Sulphur emissions from Russian Kola Peninsula smelters are known to ca use surface water acidification in the border areas between Norway and Russia. The sulphur deposition is also high in the eastern part of Fi nnish Lapland. In 1990, a monitoring programme was started to survey t he effects of acid deposition on sensitive fish populations in north-e astern Finnish Lapland. Altogether 103 sites in three areas were elect rofished 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 val ues of brooks generally exceeded 0.1 mmol/l. Brown trout, minnow and b urbot (Lota lota) were caught frequently in the study sites. Later the study was focused on the uninhabited Vatari area which is receiving t he highest sulphur deposition in Finnish Lapland. The alkalinity value s of the sampled brooks were in most cases below 0.05 mmol/l, indicati ng a decreased buffer capacity. However, the electrofishing of the bro oks showed no acid-induced damage. The lowest alkalinity values were d etected from a group of small upland ponds. In four such ponds the alk alinity was zero or negative. No minnows were caught from these four p onds apart from one, where the minnows were exceptionally large. The r esults show that the waters near the eastern border of northern Finnis h Lapland are threatened by acidification. No damage to fish populatio ns subject to fishing was observed. The absence of minnows in some sma ll waters is possibly the first sign of acid-induced fish population d amage.