ARCELLACEANS AS POLLUTION INDICATORS IN MINE TAILING CONTAMINATED LAKES NEAR COBALT, ONTARIO, CANADA

Eduard G. Reinhardt, Andrew P. Dalby, Arun Kumar and R. Timothy Patterson
Micropaleontology 43 (1997 - in press)
Ottawa-Carleton Geoscience Centre, Carleton University, Ottawa, Ontario, K1S 5B6, Canada.

Six assemblages resulting from Q-mode cluster analysis of 27 arcellacean taxa in thirty-nine sediment-water interface samples collected from two small lakes heavily polluted by mine tailings near the town of Cobalt, northeastern Ontario, Canada, correlated well with various distinct polluted and remediated environments. Results of R-mode cluster analysis indicated that arcellacean strains within the same species often discriminate among environments, thus utilization of infraspecific categories increases resolution when studying lake microenvironments, pollutants, and rates of lake remediation. Results of this study suggest that successful lake remediation in these and similarly polluted lakes is best achieved by leaving the tailings undisturbed to be buried naturally, or to speed the process by addition of an allochthonous sediment cap.

SUMMARY AND CONCLUSIONS

1. Six arcellacean assemblages were recognized that characterize distinct highly contaminated to remediated environments. As arcellaceans live at the sediment-water interface, they are highly responsive to environmental stimuli.

2. Characterization of infraspecific strains is useful to distinguish subenvironments not recognizable using species.

3. Only a thin veneer of sediments is required to protect the biota from underlying tailings in neutral pH settings. In places where this layer has been artificially removed (eg. the DWRT Assemblage), exposed contaminated substrate has not recovered as indicated by the arcellacean fauna despite the passage of 31 years (1965-1996).

4. The most effective way quickly to bring about remediation is to either leave the tailings alone or to add clean sediments to these lakes and bury the tailings.