636WG3
Xenobiotics in the Urban Water Cycle - Impact Assessment
Algal test (freshwater)
For which sample
type is it good?
Wastewater, surface water, urban runoff, pure chemcials,
mixture of chemicals
How and where to
use it?
Laboratory
Species
Unicellular freshwater green
algae e.g. Pseudokirschneriella
subcapitata (Selenastrum
capricornutum) or
Scenedesmus subspicatus
Where do the test
species live in
nature?
Surface water, fresh
Test description
The algal test is a static test (“batch-test”) with single celled
micro-algae. In the standardised test with fresh water algal
species Scenedesmus subspicatus or Selenastrum
capricornutum are used. The latter actually has the correct
taxonomic name Pseudokirchneriella subcapitata, but has also
been named Rahpidocelis subcapitata and Kirchneriella
subcapitata.
The algal test is performed by preparing different concentrations
of the test substance in a nutrient media, which ensures that
the algae can grow exponentially for the duration of the
experiment, which normally is 72 hours. Algae are added to the
various test concentrations (10,000 cells/ml) and the flasks are
incubated in artificial light and at a constant temperature (23
°C). The biomass is measured daily during tests either by
microscopy, electronic particle counting, spectrophotometry or
fluorescence measurements. The growth rate reduction can be
determined from these biomass measurements by comparing to
the growth rate of a non-inhibited control group.
The algal test is actually a test for chronic toxicity since the
biomass will be able to double 7-8 times in a 72-hour period,
i.e. the test is a multi-generation test, despite its short duration.
Standard test
procedures
ISO 8692:2004 Water quality - Freshwater algal growth
inhibition test with unicellular algae
Examples of
application on
environmental
samples
The test has been applied for a
range of environmental
samples including surface
waters, wastewaters, urban
Baun, A., Bussarawit, N., and
Nyholm, N. (1998). Screening
of Pesticide Toxicity in Surface
Water from an Agricultural
runoff, soil elutriates, landfill
leachates, and groundwater
Area at Phuket Island
(Thailand). Environmental
Pollution, 102, 185-190.
Baun, A., Jensen, S.D., Bjerg,
P.L., Christensen, T.H., and
Nyholm, N. (2000). Toxicity of
organic chemical pollution in
groundwater downgradient of
a landfill (Grindsted,
Denmark). Environ. Sci.
Technol., 34, 1647-1652.
Baun, A., Justesen, K.B., and
Nyholm, N. (2002). Algal tests
on soil suspensions and
elutriates: A comparative
evaluation for PAH
contaminated soils.
Chemosphere, 42 (2), 251258.
Christensen, A.M., Nakajima,
F., Baun, A. (2006). Toxicity of
water and sediment in a small
urban river (Store Vejleå,
Denmark). Environmental
Pollution,144 (2), 621-625.
Examples of
special test
sensitivity issues
Test materials should be soluble under test conditions.
Special care is necessary with materials of low water solubility.
For highly volatile compounds/samples a closed test with
enriched CO2 headspace may be applied (Halling-Sørensen, B.,
Nyholm, N. and Baun, A. (1996). Algal toxicity tests with volatile
and hazardous compounds in air-tight test flasks with CO2
enriched headspace. Chemosphere, 32, 1513-1526.)
WG3 contact
Anders Baun ([email protected])