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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2012-12-10 to 2012-12-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
adopted 2006
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
adopted 2009
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II)
Version / remarks:
adopted 1996
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Concentrations of the test item were analytically determined at the start and at the end of the test.
Vehicle:
yes
Details on test solutions:
Test concentrations were prepared by appropriate diluting of a saturated stock solution. This saturated stock solution was prepared with a loading rate of 1000 mg/L (i.e. 100 % v/v saturated solution) thereby simulating worst-case scenario conditions.
Based on the results of pre-experiments the following five test concentrations were tested in a geometric series (with a separation factor of 1.7): 12.0; 20.4; 34.6; 58.8; and 100.0 % v/v saturated solution (nominal).
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: 61.81 SAG (identical strains: CCAP 278/4; UTEX 1648; ATCC 22662)
- Source (laboratory, culture collection): Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, Nikolausberger Weg 18, D-37073 Göttingen, Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21.4 – 22.8 °C
pH:
7.75 – 9.98
Nominal and measured concentrations:
Five test concentrations were tested in a geometric series (with a separation factor of 1.7): 12.0; 20.4; 34.6; 58.8; and 100.0 % v/v saturated solution (nominal). Following analytical determination most of the test concentrations were below the limit of quantification. Thus, the results were based on the respective loading rates.
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks of ~250 mL volume with 100 mL test medium.
- Initial cells density: 1E04 cells/mL
- No. of vessels per concentration: three replicates per test concentration
- No. of vessels per control: three replicates
- No. of vessels per vehicle control: six replicates
- Additional test solution control: An additional test item solution control group (1.25 mg/L) without addition of algae was included in the experiment and analysed at the same occasions as the test concentrations in order to check the possibility of the adsorption of test item on algal biomass.

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- in accordance to the guideline

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuously illuminated
- Light intensity and quality: 7914 lux, which was ensured with fluorescent lamps (with a spectral range of 400 - 700 nm).

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Determination of Cell Number: The cell numbers were determined at 24, 48 and 72 hours after starting the test by manual cell counting using a microscope with counting chamber.
Morphological Changes of Algal Cells: The morphological changes of algal cells compared to the control were examined at 24, 48 and 72 hours after starting the test using a microscope.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 - < 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test concentration based on loading rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test concentration based on loading rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 100 - < 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test concentration based on loading rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 - < 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test concentration based on loading rate
Details on results:
The test item had a statistically significant inhibitory effect on the growth of Pseudokirchneriella subcapitata after the exposure period of 72 hours based on the average specific growth rate and yield at 34.6, 58.8 and 100 % v/v saturated solution (nominal). Statistically significantly difference compared to the control was not observed in the two lowest concentrations of 12.0; 20.4 v/v saturated solution (nominal). As most of the test concentrations were below the limit of quantification, the 72-hour NOEC related to growth rate and the LOEC were expressed based on the loading rate and the corresponding dilutions. Accordingly, the 72-hour NOEC related to growth rate and the LOEC value were in the range of 100 – 1000 mg/L (loading rate). Similarly, the 72-h ErC10 was determined to be in the range of 100 – 1000 mg/L (loading rate), the 72-h ErC50 to be > 1000 mg/L (loading rate). After 48 and 72 hours of exposure, smaller cells were detected at nominal concentration of 34.6 % v/v saturated solution.
Thin and swollen cells were noticed at the nominal concentrations of 58.8 and 100 % v/v saturated solution after 24, 48 and 72 hours. Additionally, pinches were observed on the cells at the highest concentration (100 % v/v saturated solution) at the 24 and 48-h observation period.
In the control and in the nominal concentrations range of 12.0 and 20.4 % v/v saturated solution abnormal appearance of algal cells was not observed during the experiment.
Results with reference substance (positive control):
The 72-h ErC50 potassium dichromate: 1.36 mg/L, (95 % confidence limits: 1.25 – 1.49 mg/L
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this acute algal growth inhibition test on Pseudokirchneriella subcapitata the observed results were the following: The 72-h EC50 value based on growth rate was determined to be > 1000 mg/L (loading rate), the 72-h NOEC value was determined to be in the range of 100 – 1000 mg/L (loading rate).
Executive summary:

The growth inhibition effect of the test item on Algae (Pseudokirchneriella subcapitata) over an exposure period of 72 hours in a static system was assessed according to OECD Guideline 201 and EU method C.3. Due to the test item's poor water solubility (maximum water solubility determined to be 0.08 mg/L), a supersaturated solution was prepared thereby simulating worst-case scenario conditions with this 72-h algal growth inhibition test with Pseudokirchneriella subcapitata. Five different concentrations arranged in a geometric series (with a separation factor of 1.7) and concurrent control group were tested. The nominal test item concentrations were 12.0; 20.4; 34.6; 58.8; and 100.0 % v/v saturated solution. The test item had a statistically significant inhibitory effect on the growth of Pseudokirchneriella subcapitata after the exposure period of 72 hours based on the average specific growth rate at 34.6, 58.8 and 100 % v/v saturated solution (nominal). Statistically significantly difference compared to the control was not observed in the two lowest concentrations of 12.0; 20.4 v/v saturated solution (nominal). As most of the test concentrations were below the limit of quantification, the results were expressed based on the loading rate. The 72-hour NOEC related to growth rate and the LOEC value were in the range of 100 – 1000 mg/L (loading rate). Similarly, the 72-h ErC10 was determined to be in the range of 100 – 1000 mg/L (loading rate), the 72-h ErC50 to be > 1000 mg/L (loading rate).

Description of key information

Under the conditions of this acute algal growth inhibition test on Pseudokirchneriella subcapitata the observed results were the following: The 72-h EC50 value based on growth rate was determined to be >1000 mg/L (loading rate), the 72-h NOEC value was determined to be in the range of 100 – 1000 mg/L (loading rate).

Key value for chemical safety assessment

Additional information

The growth inhibition effect of the test item on Algae (Pseudokirchneriella subcapitata) over an exposure period of 72 hours in a static system was assessed according to OECD Guideline 201 and EU method C.3. Due to the test item's poor water solubility (maximum water solubility determined to be 0.08 mg/L), a supersaturated solution was prepared thereby simulating worst-case scenario conditions with this 72-h algal growth inhibition test with Pseudokirchneriella subcapitata. Five different concentrations arranged in a geometric series (with a separation factor of 1.7) and concurrent control group were tested. The nominal test item concentrations were 12.0; 20.4; 34.6; 58.8; and 100.0 % v/v saturated solution. The test item had a statistically significant inhibitory effect on the growth of Pseudokirchneriella subcapitata after the exposure period of 72 hours based on the average specific growth rate at 34.6, 58.8 and 100 % v/v saturated solution (nominal). Statistically significantly difference compared to the control was not observed in the two lowest concentrations of 12.0; 20.4 v/v saturated solution (nominal). As most of the test concentrations were below the limit of quantification, the results were expressed based on the loading rate. The 72-hour NOEC related to growth rate and the LOEC value were in the range of 100 – 1000 mg/L (loading rate). Similarly, the 72-h ErC10 was determined to be in the range of 100 – 1000 mg/L (loading rate), the 72-h ErC50 to be > 1000 mg/L (loading rate).