FÖRSURNING OCH BOTTENFAUNAFÖRÄNDRINGAR I SVERIGE / Acidification and Changes in Bottom Fauna in Sweden
Benthos from lakes and running waters has been used to assess the extent of surface water acidification in Sweden 1969-1991. Altogether 2,861 different waters have been investigated. The acidification status was determined by classifying the different taxa into two groups – acid sensitive, i.e. do not tolerate pH below 5.5 and acid tolerant, i.e. tolerate pH below 5.5. Certain species of mollusks and mayflies along with the amphipod Gammarus have vanished from several waters during the observation period. The results are presented in Figure 3, where black dots indicate localities where only acid-tolerant species remained. Acidified water occurred mainly in the southern part of Sweden and in the high mountain area in the middle and northern part of the country. In the middle and northern part of Sweden the number of acidified water bodies slowly increases at altitudes above 500 m.