225-229 Snucins.p65

Chemical recovery of many anthropogenically acidified waters is occurring in Europe and North America in response to recent pollution reductions (1). These chemical improvements are particularly dramatic and well-described for the Sudbury, Ontario, Canada region including the lakes in Killarney Park (2, 3). From lakes in the Sudbury region there is also considerable evidence of natural recovery for a variety of biota including algae (4, 5), zooplankton (6, 7), and fish (8). This paper adds to this emerging body of literature on natural biological recovery by describing the recolonization of nearshore habitats by 3 benthic macroinvertebrate species; 2 mayflies (Stenacron interpunctatum, Stenonema femoratum) and an amphipod (Hyalella azteca). It is part of the Northern Lakes Recovery Study, a multidisciplinary investigation of the natural recovery of lake ecosystems from acidification (9). A unique feature of this study is the monitoring of recovery at the level of specific habitats within lakes. Other less spatially intensive studies of benthic invertebrate recovery in Sudbury area lakes indicate that species richness and densities of individual taxa tend to increase after water-quality improvement (10–12). However, by studying individual patches of habitat within lakes it was possible to quantify the time lag between chemical and biological responses, including within-lake dispersal. These types of quantitative data are required for future development of biological response models that link changes in biota to improvements in water chemistry.