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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1650

Leon A. Barmuta, Scott D. Cooper, Stephen K. Hamilton, Kim W. Kratz, and John M. Melack; Responses of zooplankton and zoobenthos to experimental acidification in a high elevation lake (Sierra Nevada, California, U.S.A.). Freshwater Biology 23:571-586, 1990

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1. During the summer of 1987 we conducted an acidification experiment using large enclosure at Emerald Lake, a dilute, high-elevation lake in the Sierra Nevada, California, U.S.A. The experiment was designed to examine the effects of acidification on the zooplankton and zoobenthos assemblages of Sierran lakes. 2. Treatments consisted of a control (pH 6.3) and pH level of 5.8, 5.4, 5.3, 5.0 and 4.7; each treatment was run in triplicate. The experiment lasted 35 days. 3. The zooplankton assemblage was sensitive to acidification. Daphnia rosea Sars emend. Richard and Diaptomus signicauda Lilljeborg decreased in abundance below pH 5.5-5.8, and virtually disappeared below pH 5.0. Bosmina longirostris (Muller) and Keratella taurocephala Ahlstrom become more abundant with decreasing pH, although B. longirostris was rare in the pH 4.7 treatment. These species might serve as reliable indicators of early acidification in lakes such as Emerald Lake. 4. The elimination of D. rosea in acidified treatments probably allowed the more acid-tolerant taxa to increase in abundance because interspecific competition was reduced. Even slight acidification can therefore alter the structure of the zooplankton assemblage. 5. In contrast to the zooplankton, there was no evidence that the zoobenthos in the enclosure was affected by acidification.