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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24.07.2017 - 08.08.2017
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
2009
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Test material form:
solid: particulate/powder

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
10 mL of blank control and 0.32 mg/L were acidified with 100 µL HNO3 (65 %) and measured undiluted.
2 mL of 1.0 mg/L were acidified with 100 µL HNO3 (65 %) and filled up on 10 mL. Accordingly, the samples were diluted 1:5.
1 mL of 3.2 mg/L were acidified with 100 µL HNO3 (65 %) and filled up on 10 mL. Accordingly, the samples were diluted 1:10.
100 µL of 10 and 32 mg/L were acidified with 100 µL HNO3 (65 %) and filled up on 10 mL. Accordingly, the samples were diluted 1:100.
100 µL of 100 mg/L were acidified with 200 µL HNO3 (65 %) and filled up on 20 mL. Accordingly, the samples were diluted 1:200.

Test solutions

Vehicle:
no
Details on test solutions:
For each treatment, 200 mL of the respective test item solution was mixed with the necessary amount of algal pre-culture (1.170 mL) to achieve a cell concentration of 3.5 *103 cells/mL. For the blank control, 350 mL nutrient medium was used instead of test item solution and mixed with the necessary amount of algal pre-culture (1.638 mL).

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
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.

Study design

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

Test conditions

pH:
Nominal Concentration in mg/L 0 h 72 h

Blank control 7.6 8.5
0.32 7.6 8.1
1.0 7.5 8.4
3.2 7.4 7.9
10 7.2 7.7
32 6.7 7.1
100 5.2 5.2
Nominal and measured concentrations:
0.32 / 1.0 / 3.2 / 10 / 32 / 100 mg/L nominal concentration
Reference substance (positive control):
yes
Remarks:
Potassium dichromate

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
< 0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
< 0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.22 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
17.09 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.02 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.51 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Reported statistics and error estimates:
Calculation of results was performed with the help of validated software ((Microsoft Excel®). The estimation of the biological data was accomplished using the software ToxRat® Professional,version 3.2.1.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
All validity criteria were met.
No observations were made which might cause doubts concerning the validity of the study outcome. The result of the test can be considered valid.
Executive summary:

One valid experiment was performed.

The study was performed using 6 concentrations ranging from 0.32 to 100 mg/L nominal concentration. Incubation time (test systemDesmodesmus subspicatus)was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield[1]were determined from the cell number at the respective observation times.

Significant inhibition of algal growth was observed in all concentrations.

 

At the start and at the end of the test and every 24 hours, the content of Zirconium as component of the test item (37.82 %) in the test solutions with and without algae was determined using ICP-analysis.

In the solution with algae, only in the three highest concentrated treatments Zirconium was measurable until the end of the test. That means the test item resp. Zirconium as component of the test item was present but not measurable in presence of the test organism.

In the solutions without algae, Zirconium was measurable in all test replicates until the end of the study. Nevertheless, the measured concentrations within the replicates were partly scattering. In the test solutions a decrease followed by an increase of the measured Zirconium concentration was observed. This might be caused by a reaction of the test item with the components of the test medium.

Nevertheless, the measured Zirconium concentration showed clear the presence of dis-solved test item in the test solution and the result of the algae test showed a clear dose-response relationship.

Because of these influences of the algae and the minerals in the medium, no calculation of the measured test item concentration based on measured Zirconium concentration was performed. The determination of the results was based on the nominal concentrations.

The 72h-EC50s of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined 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).


Yield (according to OECD Guideline 201) is defined as the biomass at the end of the exposure period minus the biomass at the start of the exposure period. Calculation see under 8.2 Growth and growth inhibition are quantified from measurements of the algal biomass as a function of time. Algal biomass is defined as the dry weight per volume, e.g. mg algae/L test solution. However, dry weight is difficult to measure and therefore surrogate parameters are used. Of these surrogates, cell counts are most often used.