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| 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 withÊH2O2,
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. |
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