Arcellaceans (thecamoebians): new tools for monitoring long- and short-term changes in lake bottom acidity

Abstract

James Lake, northeastern Ontario, Canada, has been impacted by the dumping of waste rock from a pyrite mine. High levels of Fe, Al and SO4, and low pH (2.0–5.5) are recorded in the lake. Lake configuration and current direction result in contaminated areas being restricted to the southwestern portion of the lake. Near neutral pH and low metal levels are recorded elsewhere. Analysis of arcellacean faunas from the lake indicate that one species, Arcella vulgaris, is able to thrive in even the most hostile areas of the lake. The absence of other arcellaceans indicative of contaminated substrates in higher pH lakes, such as centropyxids and Difflugia protaeiformis strains, suggests that pH is the dominant control on the distribution of this assemblage. Analysis of arcellaceans from a core at the site indicates that contamination and acidification (pH values 5.5) prevailed, but a stressed environment existed for several thousand years. The recognition that Arcellacean faunas can now be used to characterize industrially, and naturally contaminated environments of both low and high pH, provides an important new paleolimnological tool.