Biological field and laboratory methods for measuring the quality of ...

BIOLOGICAL METHODS
Ignore small cell fragments. If the slide has very
few diatoms, limit the analysis to the number of
cells encountered in 45 minutes of scanning.
When the count is completed, total the tallies
and calculate the percentages of the individual
species.
4.2 Zooplankton
4.2.1 Qualitative analysis ofzooplankton
In the initial examination, remove excess
preservative from the sample with the use of an
aspirator bulb attached to a small piece of glass
tubing whose orifice is covered with a piece of
No. 20 mesh netting. Swirl the sample, and with
a large-bore pipet, remove a portion of the
suspension and place 2 ml into each section of a
four-compartment glass culture dish (100 X 15
mm). Examine a total of 8 ml for adult
Copepoda, Cladocera, and other large forms
with the use of a binocular dissecting microscope
at a magnification of 20 to 40X. Count
and identify rotifers at a higher magnification
(lOOX). All animals should be identified to
species if possible. For qualitative analysis of
relative frequency, the following classification is
suggested:
Species in
fields, %
60 - 100
30 - 60
5 - 30
1 - 5