Impact of acid precipitation on freshwater ecosystems on Norway

Abstract

Extensive studies of precipitation chemistry during the last 20 years have clearly shown that highly polluted precipitation falls over large areas of Scandinavia, and that this pollution is increasing in severity and geographical extent. Precipitation in southern Norway, Sweden, and Finland contains large amounts of H⁺, SO₄^-2, and NO₃^-1 ions, along with heavy metals such as Cu, Zn, Cd, and Pb, that originate as air pollutants in the highly industrialized areas of Great Britain and central Europe and are transported over long distances to Scandinavia, where they are deposited in precipitation and dry-fallout. In Norway the acidification of fresh waters and accompanying decline and disappearance of fish populations was first reported in the 1920's, and since then in Sørlandet (southernmost Norway) the salmon have been eliminated from several rivers and hundreds of lakes have lost their sport fisheries. Justifiably, acid precipitation has become Norway's number-one environmental problem, and in 1972 the government launched a major research project entitled "Acid Precipitation - effects on forest and fish", (the SNSF-project). Studies of freshwater ecosystems conducted by the SNSF-project include intensive research at 10 gauged watersheds and lake basins in critical acid-areas of southern Norway, extensive surveys of the geographical extent and severity of the problem over all of Norway, and field and laboratory experiments on the effect of acid waters on the growth and physiology of a variety of organisms. Large areas of western, southern, and eastern Norway have been adversely affected by acid precipitation. The pH of many lakes is below 5.0, and sulfate, rather than bicarbonate, is the ' major anion. Lakes in these areas are particularly vulnerable to acid precipitation because their watersheds are underlain by highly resistant bedrock with low calcium and magnesium contents. Apart from the well-documented decline in fish populations, relatively little is known about the effects of acid precipitation on the biology of these aquatic ecosystems. Biological surveys indicate that low pH-values inhibit the decomposition of allochthonous organic matter, decrease the species number of phyto- and zooplankton and benthic invertebrates, and promote the growth of benthic mosses. Acid precipitation is affecting larger and larger areas of Norway. The source of the pollutants is industrial Europe, and the prognosis is a continued increase in fossil-fuel consumption. The short-term effects of the increasing acidity of freshwater ecosystems involve interference at every trophic level. The long-term impact may be quite drastic indeed.

Parent Publication

• Proceedings of the first international symposium on acid precipitation and the forest ecosystem

Citation

Wright, Richard F.; Dale, Torstein; Gjessing, Egil T.; Hendrey, George R.; Henriksen, Arne; Johannessen, Merete; Muniz, Ivar P. 1976. Impact of acid precipitation on freshwater ecosystems on Norway. In: Dochinger, L. S.; Seliga, T. A., eds. Proceedings of the first international symposium on acid precipitation and the forest ecosystem; Gen. Tech. Rep. NE-23. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 459-476