Critical Loads of Acidity to Freshwater - Fish and Invertebrates

Chemical criteria have been established for estimating critical loads of acid precipitation to surface waters. Acid neutralization capacity (ANC) was used as chemical component for describing the critical limits for biological indicators. Considerable variations in critical ANC limits are recorded for different species of fish. Perch is the species that tolerates lowest ANC-values while Atlantic salmon appears to be the most sensitive of the species surveyed. Atlantic salmon and brown trout are proposed as indicator species for fish in acidic water in Norway. An ANC-concentration of 20 µeq/l is proposed as an acceptable ANC-limit for fish and invertebrates in Norwegian freshwaters exposed to acid precipitation