Monitoring of acidification by the use of aquatic organisms

Summary

During 1981 to 1986 fish and invertebrates have been monitored in connection with acidification problems in western Norway. Based on tolerance limits of acid sensitive invertebrates, a model has been used to give measurable values of the degree of acidification in a watershed. Since 1982 a decline of acid deposition has been observed in western Norway. The effect of the decline in acidity on the aquatic community has varied depending on the degree of damage obtained during earlier acidification of the area. Results from two watersheds, not completely destroyed, are presented. In both watersheds a recovery process has been observed. The most rapid recolonization occurs among sensitive invertebrates, followed by increasing densities of young Atlantic salmon. Based on invertebrate surveys, a map of western Norway showing different levels of acidification in different areas has been constructed.