L. Lien et al., A CRITICAL LIMIT FOR ACID NEUTRALIZING CAPACITY IN NORWEGIAN SURFACE WATERS, BASED ON NEW ANALYSES OF FISH AND INVERTEBRATE RESPONSES, Science of the total environment, 177, 1996, pp. 173-193
The status of fish and invertebrate populations was analysed in the co
ntext of surface water acidification and loss of acid neutralizing cap
acity in Norwegian lakes and streams. The invertebrate data came from
165 sites, and the fish data included populations in 1095 lakes, plus
the Atlantic salmon populations in 30 rivers. The status of both fish
and invertebrates was strongly related to both acid neutralization cap
acity ANC (Sigma base cations - Sigma strong acid anions) and the conc
entration of labile aluminium. Ca2+ and TOC moderated the toxicity of
both low pH and high aluminium. The critical level of ANC varied among
fish species, with Atlantic salmon being the most sensitive, followed
by brown trout. Perch were the most tolerant of low pH/high Al-n+. At
lantic salmon status appears to be a good indicator of acidification o
f rivers, and trout is a useful indicator for lakes. Based on an evalu
ation of fish and invertebrate populations, a critical lower limit of
ANC = 20 mu equiv./l is suggested as the tolerance level in Norwegian
surface waters.