Coring, sediment processing and diatom taxonomy
Elison Lake and Col Pond were cored while still frozen with a SIPRE-CRREL drilling apparatus. Lower Dumbell Lake was cored with a miniature Glew-style gravity corer, whereas Solstice Lake was cored with a percussion corer modified for portability. Samples were processed for diatom analysis by oxidation with H2O2, H2SO4 and K2Cr2O7, followed by repeated washings with deionized water. Dilutions of these slurries were dried onto coverslips, mounted in Naphrax or Hyrax media (refractive indices >1.65) and examined at 1000X under oil immersion with differential interference or phase contrast light microscopy. Diatoms were counted to sums >500 valves per sample in transects that included slide margins. Identifications followed several taxonomic sources, principally Hustedt (1959), Foged (1981), Germain (1981), Patrick and Reimer (1966, 1975) and Krammer and Lange-Bertalot (1986-1991). These sources are supplemented by taxonomic and nomenclatural studies specific to our study areas (Douglas and Smol, 1993; Hamilton et al., 1994). Diatom concentrations were calculated for the Solstice Lake samples by the addition of a known quantity of exotic markers (Eucalyptus pollen grains) to cleaned slurries.