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Toxicity to aquatic algae and cyanobacteria

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:

March 21 - August 30, 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2011

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples of all tested concentrations were taken at test start and test end for chemical analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION:
100 mg of the test item was transferred into a sterile glass flask. 1 L of growth medium was added into the bottle and the test medium was stirred for 2 hours at room temperature (about 20°C) to achieve maximum solubility of the test item. The four other test concentrations were prepared by serial dilution with growth medium. For the control, growth medium without test item was used.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Strain: Catalog No 61.81 SAG
- Source (laboratory, culture collection): SAG, Culture Collection of Algae at Pflanzenphysiologisches Institut of the University at Göttingen, Albrecht von Haller Institut, Untere Klarspüle 2, 37073 Göttingen
- Age of inoculum (at test initiation):
- Method of cultivation: stock cultures were maintained fulfilling the criteria of the OECD guideline

ACCLIMATION
- Acclimation period: A pre-culture was reared (3 days prior to test start)
- Culturing media and conditions (same as test or not):
- Any deformed or abnormal cells observed: OECD standard growth medium

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

stable at 22.5°C

pH:

test concentrations: 8.03 - 8.11
control: 0.06 - 8.73

Nominal and measured concentrations:

The concentrations tested in the definitive test were selected based on results from the
range-finding tests.
Concentrations:
Control, 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: glass flasks
- Fill volume: 100 mL
- Initial cells density: 10 000 cells/mL
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 8

GROWTH MEDIUM
- Standard medium used: yes, sterilised synthetic growth medium acc. to OECD guideline 201

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: contionous illumination
- Light intensity and quality: 92.43 to 97.88 µE m-2 s-1

EFFECT PARAMETERS MEASURED:
The cell concentrations were determined after 24, 48 and 72 hours

TEST CONCENTRATIONS
- Range finding study: 1, 10, 100 mg/L
- Test concentrations main test: 6.25, 12.5, 25, 50, 100 mg test item/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

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

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

17.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

12.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

30.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

5.14 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

6.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Results with reference substance (positive control):

ErC50 value: 3.40 mg/L (nominal; 95% confidence limits: 2.80 – 4.13 mg/L)

Biological data were statistically analysed to determine EC₅₀ and EC₁₀ values together with 95 % confidence intervals.
The computer program ToxRat® [12] was used for statistical evaluations.

Validity criteria fulfilled:

yes

Conclusions:

The 72-hour toxicity of the test item to unicellular green algae was determined in a static system exposed to norminal contrations of 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L according to OECD 201.
The ErC50 was determined > 100 mg test item/L.

Executive summary:

The 72-hour toxicity of the test item to unicellular green algae was determined in a static system exposed to norminal contrations of 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L according to OECD 201.

The ErC50 was determined > 100 mg test item/L.

Description of key information

EC50 (growth rate) > 100 mg test item/L

Additional information

The toxicity of the test item to the green algae was tested in a study followed OECD guideline 201. The algae were exposed to nominal substance concentraions of 6.25, 12.5, 25.0, 50.0 and 100 mg test item/L for 72 hours. The concentrations of the test item in the media were confirmed by measurements of the test item at beginning of the test and at test end using a LC-MS/MS system.

The 72-hour ErC50 and ErC10 values for the inhibition of growth rate were determined to be > 100 mg test item/L and 17.1 mg test item/L, respectively. For yield, an EyC50 of 30.4 mg test item/L and an EyC10 of 5.14 mg test item/L were determined. The NOEC for growth rate and yield was at 12.5 mg test item/L.