The Effect of Altered pH on Zooplankton Community Structure in a Disturbed New Jersey Pine Barrens Pond

Abstract

The role of pH in controlling crustacean community structure (species composition and abundance) in Nescochague Lake, a disturbed New Jersey Pine Barrens pond, was experimentally investigated using in situ enclosures. Four experimental treatments were tested: acidification to pH 4.4, alkalinization to pH 7.4, alkalinization to pH 7.8 using a weak NaHCO₃ buffer, and a control (pH 6.3). Chl a and total P did not change as a result of the treatments. Zooplankton species composition did not respond in any consistent manner to the altered pH. All treatments were dominated by the same five taxa: Bosmina coregoni, Ceriodaphnia sp., Simocephalus sp., Chydorus sp., and cyclopoid copepods. There were also no significant alterations in the abundance patterns of the dominant taxa in response to changing pH. Work at other locations has shown that pH changes from 4–8 have a dramatic impact on the zooplankton community. The failure of zooplankton in Nescochague Lake to respond to these pH changes confirmed earlier work that suggested these species were pre-selected by diurnal and seasonal fluctuations of pH to be composed of only acid tolerant forms. Thus, pH had virtually no effect on these species over the ranges tested.