Crustacean zooplankton communities in lakes recovering from acidification (original) (raw)
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Can J Fisheries Aquat Sci, 1996
By comparing long-term changes in the crustacean zooplankton communities of three experimentally limed lakes near the Sudbury, Ontario, metal smelters with both temporal and spatial reference lakes distant from Sudbury, we (i) demonstrate the value of reference lakes for studies of recovery, (ii) compare univariate versus multivariate indicators of recovery, and (iii) determine if the pace of recovery was regulated by the severity of acid and metal contamination. The reference lakes provide recovery targets and norms of interannual variability. As indicators of damage and recovery, the performance of the univariate metrics was richness = diversity > evenness > abundance. Multivariate metrics were developed by projecting the Sudbury data onto a correspondence analysis of the spatial reference data. Univariate and multivariate approaches were equally sensitive for metrics based on species presence; however, the multivariate metrics incorporating the relative abundances of taxa were the best overall performers. While the two more acidic (pH 4.5) lakes had not recovered 15 years after neutralization, the zooplankton of Nelson Lake, the least acidic (pH 5.7) of the experimental lakes, recovered completely within 10 years of liming. This augurs well for the recovery of zooplankton in thousands of moderately acidic North American lakes, should international reductions in SO 2 emissions reverse their acidification.
Freshwater Biology, 2012
1. Acidification has damaged biota in thousands of lakes and streams throughout eastern North America. Fortunately, reduced emissions of sulphur dioxide and nitrogen oxides beginning in the 1960s have allowed pH levels in many affected systems to increase. Determining the extent of biological and pH recovery in these systems is necessary to assess the success of emissions reductions programmes. 2. Although there have been promising signs of biological recovery in many systems, recovery has occurred more slowly than expected for some taxa. Past studies with crustacean zooplankton indicate that a mixture of local abiotic variables, biotic variables and dispersal processes may influence the structure of recovering communities. However, most studies have been unable to determine the relative importance of these three groups of variables. 3. We assessed chemical and biological recovery of acid-damaged lakes in Killarney Park, Ontario. In addition, we assessed the relative importance of local abiotic variables, biotic variables and dispersal processes for structuring recovering communities. We collected zooplankton community data, abiotic and biotic data from 45 Killarney Park lakes. To assess the recovery of zooplankton communities, we compared zooplankton data collected in 2005 to a survey conducted for the same lakes in 1972-73 using several univariate measures of community structure, as well as multivariate methods based on relative species abundances. To determine the factors influencing the structure of recovering zooplankton communities, we used hierarchical partitioning for univariate measures and spatial modelling and variation partitioning techniques for multivariate analyses. 4. Our survey revealed significant pH increases for the majority of sampled lakes but univariate measures of community structure, such as species richness and diversity, indicated that only minor changes have occurred in many acid-damaged lakes. Hierarchical partitioning identified several variables that may influence our univariate measures of recovery, including pH, dissolved organic carbon (DOC) levels, fish presence ⁄ absence, lake surface area and lake elevation. 5. Multivariate methods revealed a shift in communities through time towards a structure more typical of neutral lakes, providing some evidence for recovery. Variation partitioning suggested that the structure of recovering copepod communities was influenced most by dispersal processes and abiotic variables, while biotic (Chaoborus densities, fish presence ⁄ absence) and abiotic variables were more important for cladoceran zooplankton. 6. Our results indicate that the recovery of zooplankton communities in Killarney Park is not yet complete, despite decades of emission reductions. The importance of variables related to acidification, such as pH and DOC, indicates that further chemical recovery may be necessary. The
Canadian Journal of Fisheries and Aquatic Sciences, 2009
Chemical recovery is hypothesized to promote rapid recovery of benthic algal communities in formerly acidified lakes; this expectation needs modification. We evaluated the hypothesis in a small lake (L302S) in the boreal forest of northwestern Ontario, Canada, during a decade of pH recovery following a prior decade of experimental acidification from pH 6.7 to 4.5. To account for regional changes during the study, we also studied a nearby reference lake (L239). Taxonomic changes in the epilithon (biofilm on rock surfaces) included persistently lower cyanobacterial biomass following its acidification-related decline and increases in both diatoms and greens. Epilithic metabolic recovery was incomplete because the acidification-induced increase in respiration continued, although the prior decline in photosynthesis was reversed. Unexpectedly, blooms of metaphytic filamentous green algae occurred at higher pH during recovery than during acidification. Although several community attributes recovered fully, recovery of many aggregate functional and taxonomic properties lagged improvements in pH. Divergence was greater at the taxonomic than at the functional level. Despite pH recovery, potential causes of incomplete algal recovery include incomplete chemical recovery and the persistent absence of functionally important biota. Our findings counter the assumption that ecological recovery mirrors the pathway of damage caused by a human stressor.
Freshwater Biology, 2010
1. Recovery of acidified aquatic systems may be affected by both abiotic and biotic processes. However, the relative roles of these factors in regulating recovery may be difficult to determine. Lakes around the smelting complexes near Sudbury, Ontario, Canada, formerly affected by acidification and metal exploration, provide an excellent opportunity to examine the factors regulating the recovery of aquatic communities. 2. Substantial recovery of zooplankton communities has occurred in these lakes following declines in acidity and metal concentrations, although toxicity by residual metals still appears to limit survival for many species. Metal bioavailability, not simply total metal concentrations, was very important in determining effects on zooplankton and was associated with a decrease in the relative abundance of cyclopoids and Daphnia spp., resulting in communities dominated by Holopedium gibberum. 3. As chemical habitat quality has improved and fish, initially yellow perch and later piscivores (e.g. smallmouth bass, walleye), have invaded, biotic effects on the zooplankton are also becoming apparent. Simple fish assemblages dominated by perch appear to limit the survival of some zooplankton species, particularly Daphnia mendotae. 4. Both abiotic (residual metal contamination) and biotic (predation from planktivorous fish) processes have very important effects on zooplankton recovery. The re-establishment of the zooplankton in lakes recovering from stress will require both improvements in habitat quality and the restoration of aquatic food webs.
Developing Conceptual Frameworks for the Recovery of Aquatic Biota from Acidification
AMBIO: A Journal of the Human Environment, 2003
Brian Leung is a research assistant professor at the University of Notre Dame. His current research focuses on ecological forecasting and bioeconomic risk analysis of invasive species, using mathematical, computational, and statistical models. His address: Bill Keller is the senior environmental scientist -Northern Lakes, with the Ontario Ministry of Environment, and is an adjunct professor in the Department of Biology, Laurentian University. His studies focus on documenting and understanding the recovery process in damaged aquatic systems, and on investigating the combined effects of multiple stressors on lakes and on lake recovery. His address: Shelley Arnott is an assistant professor in the Department of Biology at Queen's University. Her research focuses on determining the chemical and ecological factors that influence the recovery of aquatic biota from historical acidification in the face of climatic variability and the spread of nonindigenous species. Her address: John Gunn is a fisheries research scientist with the Ontario Ministry of Natural Resources and heads up the Cooperative Freshwater Ecology Unit at Laurentian University. He specializes in restoration ecology of aciddamaged ecosystems as well as the ecology of salmonid fishes of Ontario. His address: