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Ecotoxicological information

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 1996-10-15 to 1996-10-18
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Details on sampling:
- No concentrations were measured
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test was performed with an aqueous extract (eluate) of the test substance. A defined amount of the substance was weighed out and suspended in demineralized water by stirring for about 20 h (Ikamag RCT basic, step 8, at 22 ± 1 °C). Undissolved test substance was removed by filtration with a paper filter, followed by a passage through a membrane filter with a pore diameter of 0.45 µm. The test was performed with the filtrate (eluate).
- Controls: Blank control performed without test substance.
- Evidence of undissolved material: no

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: algae
- Strain: No. CHODAT SAG 86.81
- Source: Collection of algae cultures, Plant Physiological Institute of the University of Gottingen (Germany)

ACCLIMATION
- Culturing media and conditions: same as the test
- Any deformed or abnormal cells observed: no
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
23 °C ± 2 °C
pH:
- in uninoculated solution: 8
- in inoculated solution: 9.4 - 9.7
Nominal and measured concentrations:
- Nominal concentration: 0 (control) and 100 mg/L (Limit test)
- Measured concentrations: No concentrations were measured
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flask (nominal volume 250 mL) with gas-permeable silicone sponge caps
- Volume: 250 mL
- Initial cells density: 10 000 cells/mL
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to OECD guideline
- Culture medium different from test medium: no
- Intervals of water quality measurement: The pH-values were measured after 0 and 72 h in an uninoculated replicate per concentration and after 72 h in an inoculated replicate per concentration. The temperatur was measured continuously.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuous illumination
- Light intensity and quality: approx. 120 µE/(m2-s) in the wavelength range 400 - 700 nm

EFFECT PARAMETERS MEASURED: The purpose of this aquatic toxicity study was to evaluate the inhibitory effect of the test material on the growth of the freshwater green algae species, Desmodesmus subspicatus. The inhibition of the growth in relation to a control was determined over a period of 72 hours.
- Determination of cell concentrations: The algae cell densities were determined after 72 h in a counting chamber (Neubauer improved) in replicate 1 of the inoculated control.
- Chlorophyll measurement: yes. The in vivo Chlorophyll-a fluorescence was measured through pulsed excitation with light flashes having a wavelength of 435 nm after 0, 24, 48, 72 h in an EOS Filterfluorometer FL 2.

TEST CONCENTRATIONS
- Range finding study: not performed
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Exponential growth in the control: yes
- Observation of abnormalities: no
- Unusual cell shape: not observed
- Colour differences: not observed
- Flocculation: not observed
- Adherence to test vessels: not observed
- Aggregation of algal cells: not observed
- Any stimulation of growth found in any treatment: no
- Any observations that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no
Results with reference substance (positive control):
No test with reference substance was performed.

Table 1: Cell density of the algae, measured via the parameter Chlorophyll-a fluorescence. Means of the relative fluorometer units.

 

Concentration

[mg/L]

0 h

24 h

48 h

72 h

Cell density after 72 h

[% of the control]

0 (control)

40

125

657

2382

100

100

39

132

796

2697

113

 

Table 2: Inhibition of the algal growth rates after 72 hours

 

Concentration

[mg/L]

Biomass

Growth Rate

 

absolute

Inhibition [% of the control]

absolute

Inhibition [% of the control]

0 (control)

1833

0.0

0.057

0.0

100

2140

-16.7

0.059

-3.7

 

Table 3: pH-values at the start (t = 0 h) and at the end (t = 72 h) of the test

 

Concentration

[mg/L]

 

48 h

72 h

Cell density after 72 h

[% of the control]

0 (control)

8.0

8.0

9.4

100

8.0

8.0

9.7

 

Validity criteria fulfilled:
yes
Conclusions:
The test substance was tested to Desmodesmus subspicatus in a static test system according to OECD 201 (1984). Under the given conditions of this study the 72 h ErC50 value and the NOEC were determined to be > 100 mg/L.
Executive summary:

The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested according to OECD 201 (1984) under static and GLP conditions. The algae were exposed to different concentrations of test material and the growth was calculated after 0, 24, 48 and 72 hours of exposure in the test media. The study with the test substance was performed with nominal concentrations of 0 (control) and 100 mg test material/L (limit test) in reconstituted water. Because of the poor water solubility of the test substance no analytics were performed. The study design included three replicates per test material concentration, each containing about 100 mL test medium and 10,000 cells/mL at the start of the experimental phase and a control without algae. A blank control without test substance was performed. No test with reference substance was performed. Under the given conditions of this study the 72 h ErC50 and the NOEC were determined to be > 100 mg/L.

Description of key information

The test substance was tested to Desmodesmus subspicatus in a static test system according to OECD 201 (1984). Under the given conditions of this study (reference 6.1.5-1) the 72 h ErC50 value and the NOEC were determined to be < 100 mg/L.

Key value for chemical safety assessment

Additional information

The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested according to OECD 201 (1984) under static and GLP conditions. The algae were exposed to different concentrations of test material and the growth was calculated after 0, 24, 48 and 72 hours of exposure in the test media. The study with the test substance was performed with nominal concentrations of 0 (control) and 100 mg test material/L (limit test) in reconstituted water. Because of the poor water solubility of the test substance no analytics were performed. The study design included three replicates per test material concentration, each containing about 100 mL test medium and 10,000 cells/mL at the start of the experimental phase and a control without algae. A blank control without test substance was performed. No test with reference substance was performed. Under the given conditions of this study the 72 h ErC50 and the NOEC were determined to be > 100 mg/L.

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