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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:
2010-04-30 to 2010-07-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
In order to confirm correct dosage and stability of exposure concentration samples (about 50 mL) of the control and all test concentrations were taken from separate vessels including culture medium (controls), test solutions and algae at 0 h and 72 h. In order to remove the algae from the test solutions, AES-analysis was performed after centrifugation of the samples at 3950 rpm for 10 minutes, followed by dilution of the samples in deionised water to meet the linear range of the calibration lines.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
The test solutions were prepared in a dilution series from a stock solution of 100 mg/L of the test Item in culture medium for the range-finding test and from a stock solution of 400 mg/L of the test item in culture medium for the definitive test, respectively. The stock solutions and the corresponding dilutions were prepared using a mixing device (Ultra-Turrax, Janke & Kunkel; 8000 rpm, 2 minutes). The test solutions were clear at all test concentrations. The range-finding test and the definitive test were performed as static tests, i.e., without renewal of the test solutions. The controls were kept in culture-medium. Vessels including culture-medium (controls) and test solutions were kept under the same conditions as the test vessels for concentration analysis. Concentration-analysis was performed at 0 h and 72 h. The Alga-test was carried without adjustment of the pH.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus subspicatus (Chlorophyceae, Chlorococcales),
- Strain: SAG 86.81
- Source (laboratory, culture collection): Albrecht von Haller Institut für Pflanzenwissenschaften der Universität Göttingen
- Method of cultivation: Sterile on agar tubes (0.8 % Agar). Transferred to a new agar tube every 2 months.

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24.2 to 24.7 °C
pH:
in the flasks at 0 h:
8.0 to 10.9

in the flasks at 72 h:
9.6 to 10.6

The test item had a significant effect on the pH of the test solutions at the start of the exposure period.
Nominal and measured concentrations:
Nominal test concentrations: Control, 25.0 mg/L, 50.0 mg/L, 100 mg/L, 200 mg/L, 400 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks (test volume 100 mL)
- Aeration: none
- Initial cells concentration: 5000 cells/mL
- No. of vessels per test group (replicates): 3
- No. of vessels per control group (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 400 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Li2CO3
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
90 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Li2CO3
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
50 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Li2CO3
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Li2CO3
Basis for effect:
growth rate
Details on results:
The test item had a significant effect on the pH of the test solutions at the start of the exposure period. The increase of pH in the control and test concentration of 25.0 mg/L during the exposure period is caused by the growth of the algae in the test vessels. In common with other species of fresh-water algae, Desmodesmus subspicatus gains CO2 from HCO3-, leading to a release of hydroxide ions, that raised the pH of the medium. After 72 hours, the pH at test concentration of 100 mg/L had remained stable, a slight decrease of the pH was observed at test concentrations of 50, 200 and 400 mg/L when compared to the 0 hour measurements. In the test the increase of pH in the control of 2.6 (> 1.5 units as recommended in OECD-Guideline 201) had no effect on the growth of the algae as the validity criteria for algal growth were fulfilled.

Reported statistics and error estimates:
The Kolmogorov-Smirnov-test determined normality of the data (α = 0.05). The results of a one-way ANOVA showed a significant effect on the specific growth rate [µ] in the presence of lithium carbonate (F = 66.04; F critical = 5, 12, α = 0.05 = 3.11). Bartlett`s test detected homogeneity of variances (α = 0.05). Dunnett`s test for comparison of the treatment groups with the control showed significant differences between the control and the effective concentrations of 100, 200 and 400 mg/L (α = 0.05).

Concentration of the test item, cells/mL in the test flasks at 72 h, average specific growth rate [µ]over the whole testing period 0-72 h, mean value of the average specific growth rate [µ], standard deviation and coefficient of variation Vc[%], inhibition [%] and mean value of inhibition [%] of the average specific growth rate [µ] in the definitive test:

Concentration

[mg/L]

Cells / mL

Average

Specific

growth rate

[µ]

Average

Specific

growth rate

[µ]

Mean value

Standard deviation

Coefficient of variation

Vc [%]

Inhibition of Average

Specific

growth rate

[%]

Inhibition of Average

Specific

growth rate

Mean value

[%]

 

72 h

0-72 h

0-72 h

0-72 h

0-72 h

0-72 h

0-72 h

Control 1

720000

1.66

 

1.66

 

 

0.01

 

 

0.90

 

 

 

 

 

 

 

Control 2

752000

1.67

Control 3

688000

1.64

25.0

752000

1.67

 

1.68

 

 

0.01

 

 

0.82

 

-0.89

 

-1.37 *

 

25.0

808000

1.70

-2.33

25.0

752000

1.67

-0.89

50.0

512000

1.54

 

1.57

 

 

0.08

 

 

5.02

 

6.85

 

5.15

 

50.0

728000

1.66

-0.24

50.0

464000

1.51

8.83

100

312000

1.38

 

1.44

 

 

0.06

 

 

3.93

 

16.8

 

13.0 **

 

100

432000

1.49

10.3

100

400000

1.46

11.8

200

320000

1.39

 

1.33

 

 

0.06

 

 

4.49

 

16.3

 

20.0 **

 

200

224000

1.27

23.5

200

264000

1.32

20.2

400

136000

1.10

 

1.09

 

 

0.02

 

 

2.22

 

33.5

 

34.4 **

 

400

136000

1.10

33.5

400

120000

1.06

36.0

* Remark: A negative inhibition value means an enhancement of the parameter.

** Significant difference compared to the control according to Dunnett`s test (p = 0.05).

Validity criteria fulfilled:
yes
Conclusions:
In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 of lithium carbonate based on growth rate was determined as greater than 400 mg/L. The overall NOEC was determined to be 50 mg/L. The results are based on the nominal concentrations.
Executive summary:

The effect of lithium carbonate on the growth of an algal species Desmodesmus subspicatus over a 72-hour static exposure period was assessed according to OECD guideline 201. The test solutions were prepared in a dilution series from a stock solution of 100 mg/L of the test item in culture medium for the range-finding test and from a stock solution of 400 mg/L of the test item in culture medium for the definitive test, respectively. The stock solutions and the corresponding dilutions were prepared using a mixing device (Ultra-Turrax, Janke & Kunkel; 8000 rpm, 2 minutes). The test solutions were clear at all test concentrations. The controls were kept in culture medium. Vessels including culture medium (controls) and test solutions were kept under the same conditions as the test vessels for concentration analysis. Concentration analysis was performed at 0 h and 72 h. The Alga-test was carried without adjustment of the pH.AES-analysis confirmed that the test solutions were correctly dosed, i.e., the recoveries were within 92.4 to 103 % of the nominal concentrations at study start. At the end of the exposure, i.e., after 72 hours, the recoveries ranged from 95.9 to 103 % of the nominal concentrations demonstrating that the lithium concentrations were stable throughout the exposure period. Consequently, the results of the definitive test were based on nominal concentrations.In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 based on growth rate was determined as greater than 400 mg/L for lithium carbonate.

The overall NOEC was determined to be 50 mg/L for lithium carbonate (the calculated NOEC for lithium ion: 9.39 mg/L) . The results are based on the nominal concentrations.

Description of key information

In an 72-h algal growth inhibition test with Desmodesmus subspicatus according to OECD guideline 201 the 72-h EC50 based on growth rate was determined to be greater than 400 mg/L. The overall NOEC was determined to be 50 mg/L. The results were based on nominal concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:
400 mg/L
EC10 or NOEC for freshwater algae:
50 mg/L

Additional information

The effect of lithium carbonate on the growth of an algal species Desmodesmus subspicatus over a 72 hour static exposure period was assessed according to OECD guideline 201. The test solutions were prepared in a dilution series from a stock solution of 100 mg/L of the test item in culture medium for the range-finding test and from a stock solution of 400 mg/L of the test item in culture medium for the definitive test, respectively. The stock solutions and the corresponding dilutions were prepared using a mixing device (Ultra-Turrax, Janke & Kunkel; 8000 rpm, 2 minutes). The test solutions were clear at all test concentrations. The controls were kept in culture medium. Vessels including culture medium (controls) and test solutions were kept under the same conditions as the test vessels for concentration analysis. Concentration analysis was performed at 0 h and 72 h. The Alga-test was carried without adjustment of the pH.AES-analysis confirmed that the test solutions were correctly dosed, i.e., the recoveries were within 92.4 to 103 % of the nominal concentrations at study start. At the end of the exposure, i.e., after 72 hours, the recoveries ranged from 95.9 to 103 % of the nominal concentrations demonstrating that the lithium concentrations were stable throughout the exposure period. Consequently, the results of the definitive test were based on nominal concentrations.In this 72-h algal growth inhibition test with Desmodesmus subspicatus the 72-h EC50 based on growth rate was determined as greater than 400 mg/L for lithium carbonate.

The overall NOEC was determined to be 50 mg/L for lithium carbonate (the calculated NOEC for lithium ion: 9.39 mg/L) . The results are based on the nominal concentrations.

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