WATER QUALITY: Technical Information--Briefing paper on aquatic biology: "Algal growth potential" by W. Thomas Shoaf



                                             March 27, 1975

QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 75.18

Subject: WATER QUALITY: Technical Information--Briefing paper 
         on aquatic biology: "Algal growth potential" by 
         W. Thomas Shoaf

The attached description of "Algal growth potential" by 
W. Thomas Shoaf (WRD,Doraville, Ga.) represents a 
continuation of the series of briefing papers on biological 
quality initiated by the Quality of Water Branch in August, 
1974. Quality of Water Branch Technical Memorandum No. 75.17 
transmitted the provisional method for determining algal 
growth potential (AGP) and announced the availability of the 
determination from the Doraville Central Laboratory.

Please circulate the briefing paper as widely as possible in 
all district and projcct offices.



                                R. J. Pickering

Attachment

WRD Distribution: A,B,FO-L,PO,S


                  ALGAL GROWTH POTENTIAL

                      W. Thomas Shoaf

Algal growth potential is defined as the maximum algal mass 
(dry weight) that can be produced in a natural water sample 
under standardized laboratory conditions. The characteristic 
growth pattern for unicellular algae in a culture of limited 
volume is shown in Figure 1:

(See hard copy for Figure 1)

Algal growth potential is the algal mass present at 
stationary phase and is expressed as milligrams dry weight 
per litre of algae produced. Dry weight was chosen as a 
measure of algal growth because it is the most reliable 
parameter for all sample sources.

Standardization of Analysis. The determination of the algal 
growth potential of a water sample using the natural algae 
present is perhaps most desirable. The presence of these 
algae and associated microorganisms suggests that they are 
suited to survive the environment in which they live, and 
their potential for accelerated growth is of primary interest 
in many situations. The primary difficulty in using 
indigenous algae is the time required for measuring growth of 
diverse forms of algae such as colonial, filamentous, or 
unicellular forms. In some instances, water samples contain 
few algae, and the introduction of foreign algae would be 
needed to insure a growth response.

Algal growth potentials can only be compared when variables 
which affect algal growth, such as light and temperature, are 
standardized and controlled. The need for standardization of 
tcchniques for measuring algal growth potential for routine 
analysis was recognized by the Joint Industry/Government Task 
Force on Eutrophication (Bartsch, 1969). A cooperative 
developmental effort by the Soap and Detergent Association 
and the Environmental Protection Agency to produce a test for 
determining algal growth potential in natural water samples 
was the result (Bartsch, 1971). Selenastrum capricornutum was 
selected as a test organism for the following reasons: (l) It 
is a unicellular alga and its growth can be monitored 
accurately and rapidly with an electronic particle counter. 
(2) Selenastrum has been shown to tolerate acidic and 
alkaline waters as well as oligotrophic (nutrient-poor water) 
and eutrophic (nutrient rich water) conditions in aquatic 
environments (Forsberg, 1972). (3) It is listed among the 
most pollution-tolcrant algae by Palmer (1969). (4) The algal 
growth potential determined with S. capricornutum and the 
potential determined with the species indigenous to the water 
sample correlate well (Maloney and others, 1972). (5) The 
algal growth potential for various fresh water environments 
using S. capricornutum, as measured by the standard test 
(Bartsch, 1971), varies widely from 0.1 to 248 milligrams dry 
weight of algae per litre (National Lake Survey Program, 
1973).

Application. The design of a project is developed to meet a 
specific objective. All pertinent factors must be considered 
in planning if valid results and conclusions are to be 
obtained. It should be possible to evaluate algal growth 
potential data more effectively in light of other biological, 
chemical, and physical measuremcnts obtained by sampling at 
common sites. Various collection methods for streams and 
lakes have been described by Guy and Norman (1970), Goerlitz 
and Brown (1972) and Slack and others (1973).

The objectives of algal growth potential tests might include 
the establishment of baseline data or determination of the 
growth controlling nutrient(s), the influence of a nutrient, 
or the source of a nutrient when several inflows are 
involved. One of the first items that should be determined 
when measuring algal growth potential is what constitutes a 
significant change. A certain degree of variability can be 
expected with any assay or survey; however, once the baseline 
data are established, experimentation can be conducted.

The algal growth potential principle is based on Liebig's Law 
of the Minimum which recognizes that the development of a 
population is esscntially regulated by the substance 
occurring in minimal quantity relative to the requirements of 
the population. Algal growth potential measurements thus have 
been used frequently to derive information on the rcquired 
nutrients which are limiting algal growth. This type of 
measurement is usually designed to examine in detail only a 
few nutrients which preliminary testing indicates may be 
limiting or in short supply. The approach is to observe the 
effect that certain growth promoting substances (nutrients) 
have upon the algae. These substances may be of precise known 
composition (Bartsch, 1971; Miller and Maloney, 1971; Maloney 
and others, 1972) or their composition may be somewhat less 
known, such as that of an effluent which may flow into a lake 
or stream from a suspected nutrient source (Brown and others, 
1969). The practice of adding such substances to a water 
sample is called spiking. In the case of chemical spikes, it 
is obvious that if increasing amounts of a limiting nutrient 
are added to a water sample, eventually another factor 
becomes limiting. The determination of how much and what to 
spike may be made easier when the concentration of the 
nutrient(s) of interest is known. Because algal growth in 
natural water samples can be limited by one or several 
nutrients in close succession, it might be necessary to test 
spikes of combinations of nutrients that could be limiting.

When only one nutrient is limiting algal growth, it is likely 
that a correlation will be observed between the concentration 
of that nutrient and the algal growth potential. Some algal 
growth potential studies have shown correlations between 
orthophosphate and algal growth (Wang and others, 1972), 
while correlations also are likely for other nutrients in 
other aquatic environments.

Interpretation of Results. Algal growth potential data which 
are derived in the laboratory under controlled conditions of 
light and temperature do not necessarily reflect conditions 
in the natural aquatic environment from which the sample was 
taken. Only the potential at a given time can be measured. In 
nature, daily and seasonal variations in the intensity and 
duration of light occur, which can effect algal growth. 
Changes in other environmental factors can be important as 
well.  For example, the rate of algal growth roughly doubles 
with every 11!C (20!F) rise in water temperature between 0!C 
(32!F) and 32!C (90!F) (Ferguson, 1968). Growth can be 
inhibited by any suspended material, living or non-living, 
which interferes with the effective penetration of light 
essential to the algae. Grazing by invertebrates and fish, 
toxic materials entering the water, plant or animal 
excretions, or decay products from the algae themselves are 
all additional examples of factors that may inhibit growth 
potential.

In the standard procedure described by Bartsch (1971), 
membrane filtration of the water sample to remove indigenous 
algae, bacteria, fungi and any other particles which might 
interfere is required. These microorganisms contain 
nutrients, which are not available to other algae while these 
organisms are living, but later become a source of nutrients 
as a result of decay after death. Thus, it is possible to 
measure a high concentration of algae during a "bloom" but 
observe a low algal growth potential. After cell death and 
decay, the algal growth potential will probably increase. 
This, as well as the other factors mentioned above, must be 
taken into consideration when attempting to make predictions 
about future algal growth.

Summary. Algal growth potential is defined as the maximum 
algal mass (dry weight) that can be produced in a natural 
water sample under standardized laboratory conditions. Algal 
growth potential measurements are designed to establish 
baseline data, growth limiting factors (nutrients), and the 
influence and source of various growth promoting nutrients, 
so as to provide improved means for predicting and 
controlling excessive algal growth in aquatic habitats. Data 
can be compared only when the variables which control algal 
growth are standardized. Algal growth potentials derived in 
the laboratory may not reflect natural conditions because of 
insufficient light or temperature, grazing by invertebrates 
or fish, or the presence of any toxic materials. An 
understanding of the principle of the test and the factors 
that a#fect the expression of algal growth potentials is 
critical to proper data interpretation.

REFERENCES CITED

Bartsch, A. F., 1969, Provisional algal assay procedure: 
Corvallis, Oregon, U.S. Environ. Protection Agency, 61 p.

Bartsch, A. F., 1971, Algal assay procedure: bottle test: 
Corvallis, Oregon, U.S. Environ. Protection Agency, 82 p.

Brown, R. L., Bain, R. C., and Tunzi, M. G., 1969, Effects of 
nitrogen removal on the algal growth potential of San Joaquin 
valley agricultural tile drainage effluents: Paper presented 
before the Amer. Geophysical Union Nat. Meeting, San 
Francisco, Calif., 15 p.

Ferguson, F. A., 1968, A nonmyopic approach to the problem of 
excessive algal growth: Environ. Science and Technol. v. 2, 
p. 188-193.

Forsberg, C. G., 1972, Algal assay procedure: Jour. Water 
Pollution Control Federation, v. 44, p. 1623-1628.

Goerlitz, D. F.,and Brown, E., 1972, Methods for analysis of 
organic substances in water: U.S. Geol. Sur.vey Tech. Water 
Resources Inv., Bk. 5, Ch. A3, p. 2-3.

Guy, H. P.,and Norman, V. W., 1970, Field methods for the 
measurement of fluvial sedimcllts: U.S. Geol. Survey Tech. 
Water Resources Inv., Bk. 3, Ch. C2, 59 p.

Maloney, T. E., Miller, W. E., and Shiroyama, T., 1972, Algal 
responses to nutrient addition in natural waters. I. 
Laboratory assays: Nutrients and eutrophication, Special 
Symposium, Amer. Soc. ' Limnol. and Oceangr., v. 1, p. 155.

Miller, W. E.,and Maloney, T. E., 1971, Effects of secondary 
and tertiary wastewater effluents on algal growth in a lake-
river system: Jour. Water Pollution Control Federation, v. 
43, p. 2361-2365.

National Lake Survey Program, 1973, Highlights: Corvallis, 
Oregon, Environmental Protection Agency, 5 p.

Palmer, C. M., 1969, A composite rating of algae tolerating 
organic pollution: Jour. Phycology, v. 5, no. 1, p. 78-82.

Slack, K. V., Averett, R. C., Greeson, P. E., and Lipscomb, 
R. G., 1973, Methods for collection and analysis of aquatic 
biological and microbiological samples: U.S. Geol. Survey 
Tech. Water Resources Inv., Book 5, Ch. A4, 165 p.

Wang, W. C., Sullivan, W. T., and Evans, R. L., 1972, A 
technique for evaluating algal growth potential in Illinois 
surface water: Urbana, Illinois State Water Survey, Report of 
Investigation 72, 16 p.