Zooplankton Diversity and Biomass in Recently Acidified Lakes

Abstract

Ten small headwater lakes in the Adirondack Mountains of New York State and 10 in the White Mountains of New Hampshire were examined for possible effects of acidification on zooplankton. The results showed that acidification, or some close correlate, had a significant negative effect on zooplankton diversity and biomass. A loss of 2.4 species of zooplankton and 22.6 mg dry wt/m 2 was correlated with each unit decrease in pH. These results, in contrast to some previous work, show a continuous decrease in diversity and biomass over the entire range of pH in the sampled lakes, 4.5–7.2. Cladocera, with the exception of Holopedium and Polyphemus, and Epischura lacustris, Mesocyclops edax, and Cyclops scutifer, were abundant at higher pH values but rare or absent at pH values less than 5. Diaptomus minutus was predominant at pH values less than 5.Key words: acid rain, lakes, Adirondack Mountains, White Mountains, zooplankton, Cladocera, Epischura, Mesocyclops, Cyclops, Diaptomus