Assessing the Effects of Acidification on Aquatic Ecosystems: Insights from Lake Experiments

Abstract

A large number of aquatic ecosystems worldwide are acidic. In some, acidity has been generated by natural causes such as geologic processes in volcanic regions, chemical actions of mosses in sphagnum bogs, and plant decay products in brown-water habitats (Hutchinson 1957). In many other cases, however, acid conditions have been caused by human activities, which frequently have substantial consequences for ecosystems. For example, some mining processes generate acidified lakes or streams that usually occur in fairly restricted areas (e.g., McKnight and Bencala 1988; Schrenk et al. 1998). Much more widespread are situations in which acidification has been generated by atmospheric deposition contaminated with sulfuric or nitric acid that has been produced by fossil fuel burning. Such acid deposition is a relatively recently recognized phenomenon that has had major environmental consequences, particularly in regions downwind of industrial or highly populated areas (Charles 1991).