ASTM D3978-21a

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Designation: D3978 − 21 D3978 − 21a
Standard Practice for
Algal Growth Potential Testing with Pseudokirchneriella
1,2
subcapitata
This standard is issued under the fixed designation D3978; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Algae are natural inhabitants of surface waters and are found in almost every water environment
that is exposed to sunlight. The algae contribute to purification (both organic and inorganic) of streams
and lakes and are necessary as food for fish and fish food organisms. When large amounts of nutrients
are available, excessive growths referred to as “blooms” can occur. Some algal blooms release
substances toxic to fish, birds, domestic animals, and other alga. When nutrients are exhausted, the
growth of algae and production of oxygen by photosynthesis decreases. The respiration of bacteria
decomposing the large quantity of algal cells can deplete dissolved oxygen to the extent that fish and
other oxygen consumers die. Both the abundance and composition of algae are related to water quality,
with algal growth primarily influenced by the availability of nutrients.
The presence of indigenous algae in a water sample suggests that they are the most fit to survive
in the environment from which the sample was taken. The indigenous algae should produce biomass
until limited from further growth by some essential nutrient. If the indigenous algal production is
limited from further growth by an essential nutrient, the laboratory test alga cultured in a
noncompetitive environment and responding to the same limiting nutrient will produce parallel
maximum yield growth responses. Generally, indigenous phytoplankton bioassays are not necessary
unless there is strong evidence of the presence of long-term sublethal toxicants to which indigenous
3
populations might have developed tolerance (1) .
A single-indigenous algal species, dominant at the time of sampling, may not be more indicative of
natural conditions than a laboratory species that is not indigenous to the system. The dynamics of
natural phytoplankton blooms, in which the dominant algal species changes throughout the growth
season, makes it quite certain that even if the indigenous algal isolate was dominant at the time of
collection, many other species will dominate the standing crop as the season progresses.
When comparing algal growth potentials from a number of widely different water sources there are
advantages in using a single species of alga. The alga to be used must be readily available and its
growth measured easily and accurately. It must also respond to growth substances uniformly. Because
some algae are capable of concentrating certain nutrients in excess of their present need when they are
grown in media with surplus nutrients, this factor must be taken into account in selecting the culture
media and in determining the type and amount of algae to use. (2) showed that a blue-green algae
Microcystis aeruginosa, cultured in a low-nitrogen concentration medium, would not grow when
transferred to medium lacking nitrogen. However, when the alga was cultured in medium containing
four times as much nitrogen it was able to increase growth two-fold after transfer into nitrogen-free
1
This practice is under the jurisdiction of ASTM Committee E50 on Environmental Assessment, Risk Management and Corrective Action and is the direct responsibility
of Subcommittee E50.47 on Biological Effects and Environmental Fate.
Current edition approved Jan. 15, 2021Nov. 1, 2021. Published February 2021January 2022. Originally approved in 1980. Last previous edition approved 20122021 as
D3978-04 (Reapproved 2012). DOI: 10.1520/D3978-21.-21. DOI: 10.1520/D3978-21A.
2
Renamed by Gunnar Nygaard, Jirf Komárek, Jørgen Kristiansen and Olav M. Skulberg, 1986. Taxonomic designations of the bioassay alga NIVA-CHL1 ("Selenastrum
capricornutum") and some related strains. Opera Botanica 90:5-46.
3
The boldface numbers in parentheses refer to the references at the end of this practice.
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D3978 − 21a
medium. A green alga Pseudokirchnereilla subcapitata (also known as Selenastrum capricornutum
and Raphid
...