The discovery and early study of acidification of lakes in Sweden
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The discovery and early study of acidification of lakes in Sweden This article belongs to Ambio’s 50th Anniversary Collection. Theme: Acidification Brodde Almer, William Dickson
The Swedish Environmental Protection Agency was created in 1967 and at the top of its agenda was acidification. At that time, Sweden emitted more sulfur dioxide than ever before, one million tons per year. In addition, prevailing westerly wind systems brought sulfur dioxide from the industries of North-western Europe to Scandinavia. William Dickson worked at the Environmental Protection Agency’s Survey Laboratory located in Drottningholm outside Stockholm. Water samples were sent to him from committed officials at the county administrative boards and regional fishery boards in southern Sweden. They were concerned about the impaired quality of water for consumption and for fish. Dickson remembers that some lake water samples from ‘‘pristine’’ forest lakes even smelled like a petrol station and had a pH below 4. In the beginning of 1964, fisheries consultant Ulf Lundin measured a pH as low as 3.7 in the clear-water Lake Tolsjo¨n outside Gothenburg. There were no signs of pollution in the catchment area of the lake. This was the first documented case of acidification affecting fish in Sweden (Fig. 1). From the southern parts of Norway came reports in 1968 and onwards about how acid rain badly affected rivers with salmon (Salmo salar) and lakes with trout (Salmo trutta) and char (Salvelinus alpinus). Also from the Adirondack Mountains in northeastern USA came reports of severe effects on fish caused by acid rain. Brodde Almer, Institute of Freshwater Research, Drottningholm investigated in the summer of 1970, 105 brooks and rivers draining towards the Skagerrak Sea were investigated from around Gothenburg up to the border of Norway. Trout had in some waters decreased or in upper parts of streams become exterminated due to the acidification. In the autumn of 1970, pH was measured in 314 lakes at the West Coast of Sweden, many of them were severely influenced by acidification. In a subset of 50 lakes
with pH ranging from 4.40 to 7.45, a fish survey, including interviews, was performed in the summer of 1971 (Almer 1972). In the poorly buffered forest lakes, the decrease in pH was clearly harmful. In clear-water lakes, fish fauna was subject to considerable and, in certain cases, drastic changes. It became obvious that the fish stocks would be exterminated in the most acidified lakes if they were not limed. The roach (Leuciscus rutilus) proved to be a good first indicator of lake acidification since the disturbances in the reproduction that were evident at pH \ 5.5. During a survey in 1976, it was noted that, if the lakes had not been limed during the period from 1925 to 1974, 18 out of 48 stocks of roach would have been eradicated due to acidification. Perch (Perca fluviatilis) and pike (Esox lucius) were not as sensitive as the roach but still negatively affected when pH fell under 5. Fish in the brown-water (humic) lakes were
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