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

BIOLOGICAL METHODS
further identification. Small, delicate species
may be preserved in buffered 4 percent formalin
solution. Some of the more useful taxonomic
works for identification are Muenscher (1944),
Eyles and Robertson (1944), Fassett (1960) and
Winterringer and Lopinot (1966).
2.1 Qualitative Sampling
Qualitative sampling includes visual observation
and collection of representative types from
the study area. Report the extent of growth as
dense when coverage is continuous, moderate
when growths are common, and sparse when the
growth is rarely encountered. The crop of plants
may be comprised ofjust one genus or may be a
mixture; if a mixture, estimate the percentage of
individual types.
Sampling gear is varied and the choice of tools
usually depends on water depth. In shallow
water, a garden rake or similar device is very
effective for collecting macrophytes. In deeper
water, employ grabs, such as the Ekman, to
collect submersed types. In recent years, scuba
diving has gained popularity with many investigators
in extensive plant surveys. Phillips (1959)
provides detailed information on qualitative
sampling.
2.2 Quantitative Sampling
Quantitative sampling for macrophytes is
usually to determine the extent or rate of
growth or weight of growth per unit of area. The
study objectives determine whether measurements
will involve a single species or several.
Before beginning a quantitative investigation,
develop a statistical design to assist in determining
the best sampling procedure, sampling
area size, and number of samples. Often proce-
2
.dures adapted from terrestrial plant surveys are
applicable in the aquatic environment. The
following references will be helpful in adopting a
suitable technique: Penfound, 1956; Westlake,
1966; Boyd, 1969; Forsberg, 1959, 1960;
Edwards and Owens, 1960; Jervis, 1969; Blackburn,
et aI., 1968.
Standing crop. Sampling should be limited to
small, defined subareas (quadrates) with conspicuous
borders. Use a square framework with the
poles anchored on the bottom and floating line
for the sides. Collect the plants from within the
frame by hand or by using a long-handled garden
rake. Forsberg (1959) has described other
methods such as laying out long, narrow
transects.
Obtain the wet weight of material after the
plants have drained for a standard period of
time, determined by the investigator. Dry the
samples (or subsamples for large species) for 24
hours at 105°C and reweigh. Calculate the dry
weight of vegetation per unit area.
Planimeter accurate maps to determine the
total area of investigation. If additional boat or
air reconnaissance (using photographs) is done
to determine type and extent of coverage, data
collected from the subareas can then be expanded
for the total study area. Boyd (1969)
describes a technique for obtaining surface
coverage by macrophytes in a small body of
water.
Productivity. Estimate standing crops at predetermined
intervals to relate growth rates to
pollution, such as nutrient stimulation, retardation,
or toxicity from heavy metals and thermal
effects. Wetzel (1964) and Davies (1970)
describe a more accurate method with the use of
a carbon-14 procedure to estimate daily productivity
rates of macrophytes.