Long-Term Ecosystem Stress: The Effects of Years of Experimental Acidification on a Small Lake

• Published in: Science (American Association for the Advancement of Science) 1985-06, Vol.228 (4706), p.1395-1401
• Main Authors: Schindler, D. W., Mills, K. H., Malley, D. F., Findlay, D. L., Shearer, J. A., Davies, I. J., Turner, M. A., Linsey, G. A., Cruikshank, D. R.
• Format: Article
• Language: English
• Subjects: Acid deposition; Acid water pollution; Acidification; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Biomass; Ecological research; Ecosystems; Ecotoxicology, biological effects of pollution; Fresh water environment; Freshwater; Freshwater ecosystems; Freshwater fishes; Fundamental and applied biological sciences. Psychology; Lakes; Lentic systems; Phytoplankton; Plankton; Pollution; Trout
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.228.4706.1395

Experimental acidification of a small lake from an original pH value of 6.8 to 5.0 over an 8-year period caused a number of dramatic changes in the lake's food web. Changes in phytoplankton species, cessation of fish reproduction, disappearance of the benthic crustaceans, and appearance of filamentous algae in the littoral zone were consistent with deductions from synoptic surveys of lakes in regions of high acid deposition. Contrary to what had been expected from synoptic surveys, acidification of Lake 223 did not cause decreases in primary production, rates of decomposition, or nutrient concentrations. Key organisms in the food web leading to lake trout, including Mysis relicta and Pimephales promelas, were eliminated from the lake at pH values as high as 5.8, an indication that irreversible stresses on aquatic ecosystems occur earlier in the acidification process than was heretofore believed. These changes are caused by hydrogen ion alone, and not by the secondary effect of aluminum toxicity. Since no species of fish reproduced at pH values below 5.4, the lake would become fishless within about a decade on the basis of the natural mortalities of the most long-lived species.