Acid rain: impacts on populations and communities

Posted on September 22, 2010

Surprisingly few studies have attempted to relate population-level impacts of environmental stress (e.g., effects on genetic diversity) with those at the community level, such as changes to species  diversity.  Lakes in  Ontario, Canadahave been used to examine relationships between environmental stress (acidity) and the genetic and species diversity of zooplankton.  These lakes are valuable sites for such studies because they display a wide range of pH levels as a result of the modifying effects of local geology on the responses of water bodies to acid rain.  Species diversity was measured by collecting zooplankton in vertical net hauls starting near the lake bottom, and genetic diversity was measured by using a mitochondrial DNA tag to distinguish different haplotypes (linked genetic markers) of the common copepod Leptodiaptomus minutus.  Low pH was predicted to reduce community richness by excluding acid-intolerant species, and to lower genetic diversity by reducing population size and increasing genetic drift.  Although acid-related variables could be related to both species diversity and genetic diversity, they had a strong effect only on species diversity.  While limitations on dispersal didn’t affect the diversity of species within zooplankton communities, they did seem to influence the distribution of Leptodiaptomus variants, which was driven mainly by the spatial separation and isolation of lakes.

 Reference:  Derry, A.M., Arnott, S.E., Shead, J.A., Hebert, P.D.N. & Boag, P.T.  2009.   Ecological linkages between community and genetic diversity  in zooplankton among boreal shield lakes.  Ecology  90(8), 2275–2286.