LONG-TERM TRENDS IN STREAM CHEMISTRY AND BIOLOGY IN NORTHEAST SCOTLAND - EVIDENCE FOR RECOVERY

Since 1983 stream chemistry and macroinvertebrate ecology were monitor ed in ten streams draining the eastern Cairngorms. All streams have ex hibited a decline in sulphate concentrations in response to reduced ac id deposition; in the more acidic systems this has been reflected by a parallel increase in acid neutralizing capacity (ANC). in some stream s this coincides with an increase in the abundance of acid-sensitive m ayflies which may provide evidence for biological recovery. In the mos t chronically acidified systems no increased abundance has been observ ed despite significant increases in ANC. This suggests that further re ductions in deposition and sufficient time for a reversal of soil acid ification is required before any biotic recovery occurs.