Lakes near Wawa, Ontario (48°00′N, 84°45′W; Fig. 1) present a rare opportunity for studying chemical and biological recovery patterns in an area with a naturally occurring high buffering capacity. Despite the presence of carbonate-bearing bedrock within some lake catchments, the acid-neutralizing capacity of some lakes was exceeded (Gordon and Gorham 1963; Rao and LeBlanc 1967; Somers and Harvey 1984) during a period of intense iron sintering from 1939 to 1998. Acidified lakes reached extremely low pH values of