Biological, Chemical and Physical Responses of Lakes to Experimental Acidification

Abstract

Changes in physical, chemical and biological factors were observed during a 5-yr experimental acidification study in Lake 223 of the Experimental Lakes Area, and compared to a 2 yr pre-acidification period. Significant changes included increased transparency, rates of hypolimnion heating and rates of thermocline deepening; increased concentrations of Mn, Na, Zn, Al, and chlorophyll; decreased concentrations of suspended C, total dissolved N, Fe and chloride; increases in Chlorophyta but decreases in Chrysophyta; the disappearance of the opossum shrimp Mysis relicta and the fathead minnow Pimephales promelas; the appearance of epidemics of the filamentous alga Mougeotea; decreased fitness and decline in numbers of Orconectes virilis; and increased embryonic mortality of the lake trout Salvelinus namaycush.