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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From November 22, 2016 to November 25, 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
see 'Any other information on materials and methods'
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
yes
Remarks:
see 'Any other information on materials and methods'
GLP compliance:
yes
Analytical monitoring:
yes
Remarks:
DOC determination using a TOC analyser
Details on sampling:
At the start and at the end of the test, the content of the test substance in the test solutions was determined using DOC determination.
Vehicle:
no
Details on test solutions:
For the 1st experiment individual water-accommodated fractions (WAF) were prepared for the test. This was done by mixing the nominal loads with the corresponding amount of algal medium (demineralised water enriched with minerals but without algae) and shaking vigorously for 23 h. The resulting solutions were filtered through 0.45 μm nylon filters. For the 2nd experiment a water-accommodated fraction (WAF) at 100 mg/L nominal load was prepared. This was done by mixing 100 mg/L of test substance with the corresponding amount of algal medium (demineralised water enriched with minerals but without algae) and shaking vigorously for 24 h. The resulting solution was filtered through 0.45 μm nylon filters. The lower concentrations were prepared by serial dilution of this stock solution.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Unicellular freshwater green alga.
Genus: Desmodesmus;
Species: subspicatus;
SAG Strain Number: 86.81;
Taxonomic position: Chlorophyta - Chlorophyceae;
Origin and Culture: The culture of Desmodesmus subspicatus was obtained in January, 2016 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 2 - 8°C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
not specified
Test temperature:
22.4 – 22.5°C
pH:
7.6 - 7.8
Dissolved oxygen:
not specified
Salinity:
not specified
Conductivity:
not specified
Nominal and measured concentrations:
First experiment in mg/L:
Nominal: 1.0; 3.2; 10.0; 32.0; 100.0
Measured: 1.1; 3.4; 10.2; 35.2; 101.6

Second experiment in mg/L:
Nominal: 100.0
Measured: 101.6
Details on test conditions:
In the first experiment: 1.0 to 100 mg/L (nominal);
In the second experiment: treatment concentrations were prepared from serial dilution of a 100 mg/L (nominal) solution
Reference substance (positive control):
yes
Remarks:
Potassium dichromate K2Cr2O7
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
51 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
12 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
3.2 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.:
1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
8.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
2.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
In the first experiment inhibition in all tested concentrations was within the same range and no dose response could be observed. Therefore, the study was repeated.
Results with reference substance (positive control):
Potassium dichromate (K2Cr2O7) was used as positive control in a separate reference test. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).
Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the 72 h nominal EC50 and NOEC of the substance to Desmodesmus subspicatus were determined to be 51 mg/L and 3.2 mg/L (based on growth rate) respectively.
Executive summary:

A study was conducted to determine the toxicity of the substance to Desmodesmus subspicatus according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Two valid experiments were performed. Individual water-accommodated fractions (WAF) were prepared for the test. The study was conducted using 5 test concentrations ranging from 1.0 to 100 mg/L (nominal), with an incubation time of 72 h. The measured concentrations (determined by measurement of dissolved organic carbon, DOC) were comparable to the nominal ones. The cell concentration of each replicate was determined by measuring the cell numbers every 24 h with an electronic particle counter. Growth rate and yield were determined from the cell number at the respective observation time. Significant inhibition of algal growth was observed at all concentrations, except the lowest concentration of 1 mg/L (nominal). Under the study conditions, the 72 h nominal EC50 and NOEC of the substance to Desmodesmus subspicatus were determined to be 51 mg/L and 3.2 mg/L (based on growth rate) respectively (Muckle, 2017).

Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
51 mg/L
EC10 or NOEC for freshwater algae:
3.2 mg/L

Additional information

A study was conducted to determine the toxicity of the substance to Desmodesmus subspicatus according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Two valid experiments were performed. Individual water-accommodated fractions (WAF) were prepared for the test. The study was conducted using 5 test concentrations ranging from 1.0 to 100 mg/L (nominal), with an incubation time of 72 h. The measured concentrations (determined by measurement of dissolved organic carbon, DOC) were comparable to the nominal ones. The cell concentration of each replicate was determined by measuring the cell numbers every 24 h with an electronic particle counter. Growth rate and yield were determined from the cell number at the respective observation time. Significant inhibition of algal growth was observed at all concentrations, except the lowest concentration of 1 mg/L (nominal). Under the study conditions, the 72 h nominal EC50 and NOEC of the substance to Desmodesmus subspicatus were determined to be 51 mg/L and 3.2 mg/L (based on growth rate) respectively (Muckle, 2017).