SS3.12 Large Scale Ecosystem Manipulations
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
TurnerMA, Experimental Lakes Area / Fisheries and Oceans, Winnipeg, Canada, turnermi@dfo-mpo.gc.ca
Paterson, M, J, Experimental Lakes Area / Fisheries and Oceans, Winnipeg, Canada, patersonm@dfo-mpo.gc.ca
Findlay, D, L, Experimental Lakes Area / Fisheries and Oceans, Winnipeg, USA, findlayd@dfo-mpo.gc.ca
Mills, K, H, Experimental Lakes Area / Fisheries and Oceans, Winnipeg, Canada, millsk@dfo-mpo.gc.ca
Hendzel, L, L, Experimental Lakes Area / Fisheries and Oceans, Winnipeg, Canada, hendzell@dfo-mpo.gc.ca
McNicol, D, K, Environmental Conservation Branch / Canadian Wildlife Service, Nepean, Canada, don.mcnicol@ec.gc.ca
Hann, B, J, University of Manitoba, Winnipeg, Canada, hann@Ms.UManitoba.CA
Vinebrooke, R, D, University of Regina, Regina, Canada, rolf.vinebrooke@uregina.ca
Watkins, E, M, Experimental Lakes Area / Fisheries and Oceans, Winnipeg, Canada, watkinse@dfo-mpo.gc.ca
 
BIOLOGICAL RECOVERY AND DISORDER IN A BOREAL FOREST LAKE RECOVERING FROM ACIDIFICATION
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We studied the recovery from acidification of biological populations in a boreal forest lake in northwestern Ontario, Canada. After a decade of sulfuric acidification during which we lowered the pH gradually from ~6.8 to 4.5, we allowed the epilimnetic pH to increase stepwise to 5.1, 5.8, 6.2 and 6.8 during the next decade. Despite some recovery with the increase in pH, symptoms of disturbance remained. Features of this disturbance included: lags in recovery of several biological properties; hysteresis in recovery trajectories (recovery was not monotonic with pH); increased variability in biotic composition and function; different responses between littoral and pelagic communities; and persistent reductions in biocomplexity. The duration and features of recovery were often difficult to predict because of constraints on recruitment of extirpated biota, food web restructuring, and because some features of recovery were indirect consequences of acidification caused by physical and chemical changes rather than pH alone.