Phytoplankton of the seasonal surveys of 1977, and further pre- vs. post-operational comparisons at Cook Nuclear Plant / John C. Ayers, Susan J. Wiley.

The once-settled sample is then diluted if need be and settled again,
this time in 18-ml cylinders. These cylinders are attached with a small
amount of stopcock lubricant (to prevent leakage) to the microscope slides
which rest on an aluminum plate one quarter inch thick. The whole apparatus
is then secured together mechanically. The microscope slides, prior to
having the cylinders placed on them, were treated with Dessicote to provide a
hydrophobic surface to the slide. After the samples have settled overnight,
the aluminum plate on which they rest is placed on a block of dry ice for 90
seconds or less. This freezes the bottom 1-1.5 ml. The unfrozen part is
then discarded and the cylinders are removed from the slides. The slides are
then placed in an anhydrous ethanol chamber for 2 days, and then in a toluene
chamber for 2 days.
The first chamber removes the excess water and the second prepares the
samples for their final mounting in toluene based Permount. One drop of
Permount is put on the slide, a cover slip is then placed over it, and the
slide is allowed to dry for two days or more.
The specimens are counted, at 1200X under oil immersion on a Leitz
Ortholux microscope, to species, variety and form when practical, otherwise
to genus or group. Only those specimens that appear to have been viable at
the time of collection are counted. Two sweeps of the slide are made, one
vertical and one horizontal. This provides an indication of the randomness
of the species on the slide.
All species are counted to individual cells, except for filamentous
blue-green algae with cylindrical trichomes which are counted as individual
organisms. Prior to 1974 all colonial blue-greens were counted as single
organisms; the change in counting resulted in an apparent increase of
blue-greens beginning in 1974.

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