Trajectories of zooplankton recovery in the Little Rock Lake whole-lake acidification experiment.

Trout Lake Station, Center for Limnology, University of Wisconsin, 10810 County Highway N, Boulder Junction, Wisconsin 54512, USA.
Ecological Applications (Impact Factor: 4.13). 03/2006; 16(1):353-67. DOI: 10.1890/04-1800
Source: PubMed

ABSTRACT Understanding the factors that affect biological recovery from environmental stressors such as acidification is an important challenge in ecology. Here we report on zooplankton community recovery following the experimental acidification of Little Rock Lake, Wisconsin, USA. One decade following cessation of acid additions to the northern basin of Little Rock Lake (LRL), recovery of the zooplankton community was complete. Approximately 40% of zooplankton species in the lake exhibited a recovery lag in which biological recovery to reference basin levels was delayed by 1-6 yr after pH recovered to the level at which the species originally responded. Delays in recovery such as those we observed in LRL may be attributable to "biological resistance" wherein establishment of viable populations of key acid-sensitive species following water quality improvements is prevented by other components of the community that thrived during acidification. Indeed, we observed that the recovery of species that thrived during acidification tended to precede recovery of species that declined during acidification. In addition, correspondence analysis indicated that the zooplankton community followed different pathways during acidification and recovery, suggesting that there is substantial hysteresis in zooplankton recovery from acidification. By providing an example of a relatively rapid recovery from short-term acidification, zooplankton community recovery from experimental acidification in LRL generally reinforces the positive outlook for recovery reported for other acidified lakes.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Phytoplankton and littoral invertebrate assemblages in 4 boreal lakes recovering from acidification and 4 minimally disturbed reference lakes studied over 2 decades were used to determine the pathways and trajectories of change under the influence of climatic variability. Assemblage composition (species presence–absence data) but not dominance patterns (invertebrate abundance/phytoplankton biovolume) of acidified lakes became more similar to those of reference lakes (distance decreased with time), indicating that detection of recovery varies as a function of chosen metrics. Acidified lakes had more pronounced shifts in assemblage composition than did reference lakes. The most marked differences were noted for phytoplankton assemblages. Assemblages in acidified lakes had mean between-year Euclidean distances almost 2× greater than those of assemblages in reference lakes. Trends in water chemistry showed unequivocal recovery, but responses of phytoplankton and invertebrate assemblages, measured as between-year shifts in assemblage composition, were correlated with interannual variability in climate (e.g., North Atlantic Oscillation, water temperature) in addition to decreased acidity. The finding that recovery pathways and trajectories of individual acidified lakes and the environmental drivers explaining these changes differed among assemblages shows that biological recovery is complex and the influence of climatic variability is poorly understood.
    Journal of the North American Benthological Society 12/2010; 29(4):1472-1490. · 2.71 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Biological recovery of aquatic ecosystems from acidification damage is a slow process. In lakes near the massive Cu and Ni smelters in Sudbury, Canada, the delays might be caused by residual metals, habitat damage, altered predator–prey interactions, or other persistent ecological stressors. Assessments of benthic invertebrate communities in 24 Sudbury lakes were conducted to evaluate the relative importance of these delaying factors. At the time of sampling, all lakes had chemically recovered to a pH >6.0, but they varied widely in the duration of time above this threshold and in current metal concentrations, watershed contributions of organic matter, littoral habitat composition, and fish community composition. A model developed with redundancy analyses (RDA) of 4 groups of environmental variables (i.e., water chemistry, fish communities, physical lake descriptors, and littoral habitat) accounted for 74.9% of the variance in benthic invertebrate community metrics across these environmental gradients. Fish species richness, duration of pH recovery, and % boulder habitat were the most significant variables and explained 22%, 9%, and 8% of the variance in benthic invertebrate community metrics, respectively. Damaged systems clearly need sufficient time to recover from severe disturbances. However, our study suggests that remediation techniques, such as manipulation of predator–prey interactions through fish introductions, might speed the recovery of benthic invertebrate communities.
    Journal of the North American Benthological Society 06/2010; 29(2):572-585. · 2.71 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Regional acidification of aquatic habitats has caused severe reductions in biodiversity. Reduced sulfur dioxide emissions over the past several decades have resulted in increased pH and alkalinity in some areas of North America and Europe. However, biological recovery has lagged behind increases in lake pH. We propose that acidification-induced changes in predator assemblages can provide biological resistance to recovery of assemblages in lower trophic levels in lakes. Many recovering lakes remain fishless because of low colonization rates and, therefore, support a high abundance of macroinvertebrate predators that may have a large impact on zooplankton community structure. We assessed the distribution of water beetles in relation to pH and presence/absence of fish in 29 lakes on the Canadian Shield. We found that water beetle assemblage composition was not related to pH. However, the occurrence of fish was significantly negatively correlated with water beetle distribution, particularly for the predaceous diving beetle, Graphoderus liberus. Mesocosm experiments in Swan Lake, a fishless lake recovering from acidification, revealed that larval G. liberus can reduce total zooplankton abundance, species richness, and species diversity. In particular, the densities of 4 taxa (Leptodiaptomus minutus, Diaphanosoma birgei, Bosmina (Bosmina) spp., and calanoid copepodids) were reduced by larval G. liberus predation. The high abundance of G. liberus in the absence of fish and the impact of larval G. liberus predation on crustacean zooplankton in Swan Lake suggest that biological resistance may be an important impediment to the recovery of aquatic food webs, despite increasing pH.
    Journal of the North American Benthological Society 12/2006; 25(4):811-824. · 2.71 Impact Factor


1 Download
Available from