QUINLAN, ROBERTO, PETER R. LEAVITT, ARUNA S. DIXIT, ROLAND I. HALL, and JOHN P. SMOL Landscape Effects of Climate,Agriculture, A
Limnol. Oceanogr., 47(2), 2002, 378±391 q 2002, by the American Society of Limnology and Oceanography, Inc. Landscape effects of climate, agriculture, and urbanization on benthic invertebrate communities of Canadian prairie lakes Roberto Quinlan1 Paleoecological Environmental Assessment and Research Laboratory (PEARL), Department of Biology, Queen's University, Kingston, Ontario, Canada, K7L 3N6 Peter R. Leavitt Limnology Laboratory, Department of Biology, University of Regina, Regina, Saskatchewan, Canada, S4S 0A2 Aruna S. Dixit Paleoecological Environmental Assessment and Research Laboratory (PEARL), Department of Biology, Queen's University, Kingston, Ontario, Canada, K7L 3N6 Roland I. Hall2 Limnology Laboratory, Department of Biology, University of Regina, Regina, Saskatchewan, Canada, S4S 0A2 John P. Smol Paleoecological Environmental Assessment and Research Laboratory (PEARL), Department of Biology, Queen's University, Kingston, Ontario, Canada, K7L 3N6 Abstract Paleoecological analyses of fossil chironomid assemblages from eight lakes of the Qu'Appelle Valley, Saskatch- ewan, Canada, were used to quantify the relative in¯uence of climate, resource use, and urbanization on benthic invertebrate communities 1850±1995. Fossil analyses inferred that Qu'Appelle lakes are naturally productive but that invertebrate communities were altered by agriculture and urbanization. In western lakes, rates of community change (chord distance per 5 yr) were low and nonsigni®cant (P . 0.05) prior to European settlement, but increased twofold after ;1930±1940. In contrast, uniformly signi®cant rates of community change were recorded in eastern downstream lakes only after the 1960s. In both cases, high rates of change corresponded to alterations in the balance between deep-water (Chironomus) and littoral species (Cladotanytarsus mancus group, Tanytarsus s.lat.
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