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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From October 09, 1998 to October 21, 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1998
Report Date:
1998

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
(modified for coloured test substance)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
Duplicate samples were taken at the start of the test from the freshly prepared test media (without algae) of all the concentrations and from the control.

Test solutions

Vehicle:
no
Details on test solutions:
The test medium of the highest test concentration of nominal 100 mg/L was prepared dissolving 100 mg of test substance completely in 1000 mL test water by stirring for 15 minutes.

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Scenedesmus subspicatus
- Strain: CHODAT (86.81 SAG)
- Source (laboratory, culture collection): Sammlug von algenkuturen, pfanzenphysiologisches insstitutder, Universitat Gottingen.
- Age of inoculum (at test initiation): 3 d
- Method of cultivation: according to test guideline.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h

Test conditions

Hardness:
24 mg/L CaCO3
Test temperature:
23˚C
pH:
8 to 8.9
Nominal and measured concentrations:
Nominal concentrations: 100, 32, 10, 3.2, 1.0 and 0.32 mg/L
Details on test conditions:
The test was started (0 h) by inoculum of a biomass of 10,000 algal cells per mL test medium. These cells were taken from an exponentially growing pre culture, which was set up about 3 d prior to the test at the same conditions as the test.

The performed in Erlenmeyer flasks (50mL), each with 15 mL algal suspension continuously stirred by magnetic stirrers, 3 flasks per test concentrations and 6 flasks in the control. Each Erlenmeyer flask was placed in black cylinder, coasted inside with ammonium foil. The cylinders were covered with glass dishes, the dishes were covered with watch glass dishes to prevent evaporation.
Reference substance (positive control):
not specified

Results and discussion

Effect concentrations
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

Any other information on results incl. tables

Results:

Experiment part A
Parameter (0-72 h) Biomass (mg/L) Growth rate (mg/L)
EC50 (95% conf limits) >100 >100
EC10 (95% conf limits) 3.4 (0.1 -11) 18 (4.7 -57)

Experiment part B
Parameter (0-72 h) Biomass (mg/L) Growth rate (mg/L)
EC50 (95% conf limits) >100 >100
EC10 (95% conf limits) 7.4 (2 -15) 30 (15 -63)

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The modified test demonstrated that the observed algal growth inhibition had an indirect cause, namely the light filter effect of the coloured test substance. Toxic effects of the test substance could be excluded up to the highest concentration of 100 mg/L. The ErC50 was therefore > 100 mg/L. The substance was neither found acutely nor chronically toxic to freshwater green algae.
Executive summary:

A study was conducted to determine the toxicity of the test substance to freshwater algae according to a modified version of OECD Guideline 201, in compliance with GLP. Desmodesmus subspicatus cells were exposed for 72 h under static conditions at concentrations of 100, 32, 10, 3.2, 1.0 and 0.32 mg/L. All test media were slightly to strongly coloured by the test substance. Analytical dose verification was conducted using spectrophotometry. The mean measured concentrations in the analysed test media varied from 94 to 98% of nominal values. Therefore, all biological results were related to nominal concentrations. The same inhibition of Desmodesmus subspicatus was observed when the algae grew in test water without test substance, but under reduced light intensities by the filter effect of the coloured test media as in the second parallel experimental part, where the algae grew in the test media was dissolved test substance. Thus, the modified test demonstrated that the observed algal growth inhibition had an indirect cause, namely the light filter effect of the coloured test substance. Toxic effects of the test substance could be excluded up to the highest concentration of 100 mg/L. The ErC50 was therefore > 100 mg/L (nominal) (Peither, 1998).