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

BIOLOGICAL METHODS
When making waste management decisions, it
is important to consider and tentatively define
the persistence of a pollutant. Materials that
have half lives less than 48 hours can be termed
as rapidly decaying compounds; those with half
lives greater than 48 hours but less than 6
months, as slowly decaying; and those compounds
in natural waters with half lives longer
than 6 months, as long-lived persistent materials.
Bioassays can be conducted over almost any
interval of time, but the test duration must be
appropriate to the life stage or life cycle of the
test organisms and the objectives of the investigation.
The purpose of short-term tests, such as
acute mortality tests, is to determine toxicant
concentrations lethal to a given fraction (usually
50 percent) of the organisms during a short
period of their life cycle. Acute mortality tests
with fish generally last about 4 to 7 days. Most
toxicants, however, cause adverse effects at
levels below those that cause mortality. To meet
this need, long-term (chronic) tests are designed
to expose test organisms to the toxicant over
their entire life cycle and measure the effects of
the toxicant on survival, growth, and reproduction.
Sometimes only a portion of the life cycle
is tested, such as studies involving growth or
emergence of aquatic insects. With fish, such
tests usually last for 30, 60, or 90 days and are
often termed subacute.
Laboratory bioassays may be conducted on a
"static" or "continuous flow" basis. The specific
needs of the investigator and available test facilities
determine which technique should be used.
The advantages and applications of each have
been described in Standard Methods, (APRA,
1971) and by the National Technical Advisory
Committee (1968). Generally, the continuousflow
technique should be used where possible.
Apparatus advantageous for conducting flowthrough
tests includes diluters (Mount and
Warner, 1965; Mount and Brungs, 1967), valve
controlling systems (Jackson and Brungs, 1966)
and chemical metering pumps (Symons, 1963).
The biological effects of many industrial
wastes are best evaluated in the field; transporting
large volumes of industrial wastes to a
laboratory for bioassay purposes can be impractical.
Testing facilities are best located at the site
2
of the waste discharge. A bioassay trailer
(Zillich, 1969) has proven useful for this purpose.
In situ bioassay procedures are also a good
method for defining the impact to aquatic life
below the source of industrial waste discharges
(Basch, 1971).
Biomonitoring, a special application of biological
tests, is the use of organisms to provide
information about a surface water, effluent, or
mixtures thereof on a periodic or continuing
basis. For the best results, biomonitoring should
maintain continuous surveillance with the use of
indigenous species in a flow-through system
under conditions that approximate the natural
environment.
2.0 PHYTOPLANKTON - ALGAL ASSAY
The Algal Assay Procedure: Bottle Test was
published by the National Eutrophication Research
Program (USEPA, 1971) after 2 years of
intensive evaluation, during which excellent
agreement of the data was obtained among the 8
participating laboratories. This test is the only
algal bioassay that has undergone sufficient evaluation
and retlnement to be considered reliable.
The following material represents only a brief
outline of the test. For more explicit details, see
the references.
2.1 Principle
An algal assay is based on the principle that
growth is limited by the nutrient that is present
in shortest supply with respect to the needs of
the organism. The test can be used to identify
algal growth-limiting nutrients, to determine
biologically the availability of algal growthlimiting
nutrients, to quantify the biological
response (algal growth response) to changes in
concentrations of algal growth-limiting nutrients,
and to determine whether or not various
compounds or water samples are toxic or inhibitory
to algae.
2.2 Planning Algal Assays
The specific experimental design of each algal
assay is dictated by the particular problem to be
solved. All pertinent ecological factors must be
considered in planning a given assay to ensure
that valid results and conclusions are obtained.