Reduction in fitness of the gastrotrichLepidodermella squammataby dilute acid mine water and amelioration of the effect by carbonates

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Abstract
Individuals from a clone of Lepidodermella squammata were cultured in lake water (control) and 6 solutions of dilute acid mine water with constant conductivity but varying carbonate content. Life table data were analysed based on a cohort of 45 animals for each treatment. Animals were able to survive briefly in dilute acid mine water (370/imho/cm total conductivity) with levels of carbonate below 12 ppm. At higher levels of carbonate, survival was similar to controls, and reproduction increased significantly with increasing carbonate level over the range tested, 13–67 ppm, with a plateau in the mid- range of 17–47 ppm. Mean number of eggs per female in the control and the 4 test solutions supporting reproduction was directly related to carbonate level, while variance was inversely related to carbonate level. Both environmental and genetic sources for the observed variability were minimized experimentally. Nevertheless, increased selection pressure, occurring in the presence of dilute acid mine water through the medium of lowered carbonates, appeared to be expressed through increased variability in egg production within a cohort.