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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
2011
GLP compliance:
yes (incl. certificate)
Remarks:
Sächsische Staatsministerium für Umwelt und Landwirtschaft, Germany
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0 and 100 mg/L
- Sampling: at the start and at the end of the test
- Sample storage conditions before analysis: samples were frozen
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution was prepared by weighing 100.0 mg test item and filling up to approx. 990 mL with test medium and mixing well. 6.45 mL algal inoculum (measured 77.5 x 104 cells/mL) were added and test medium was added to a total volume of 1000 mL.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: freshwater green algae
- Source (laboratory, culture collection): purchased from “Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Experimentelle Phykologie und Sammlung von Algenkulturen” at the University of Göttingen, Germany, in July 2009, strain: 86.81 SAG (further cultivation in the test facility)
- Breeding: glass flasks with 1000 mL growth medium (OECD medium) kept at 24 ± 2°C with continuous illumination of universal white-type fluorescent light (400-700 nm), intensity: approx. 70 μE·m-2·s-1
- Conditions of the algae used in the test: cultures in logarithmic growth phase

ACCLIMATION
Axenic stock cultures grew in culturing vessels for 3 days prior to test initiation; cultivation was performed in glass flasks with the medium described above; algae were kept at the same temperature and light culturing conditions as during the test.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
22.6 - 23.4 °C
pH:
8.11 - 9.4
Nominal and measured concentrations:
Nominal: 0 and 100 mg/L
Recoveries: 91.2% at 0 h and 88.5% at 72 h
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flask
- Type (delete if not applicable): closed with air-permeable stoppers
- Material, size, headspace, fill volume: 250 mL Erlenmeyer flask, 100 mL test volume, headspace: 150 mL
- Initial cells density: 5000 cells/mL in each replicate
- Control end cells density: 1186700 cells/mL (mean)
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no
- Intervals of water quality measurement: temperature recorded continuously, pH at the start and at the end

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: continuous illumination
- Light intensity and quality: on average 106 μE m-2 s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: actual microscopic cell count using a Neubauer counting chamber, at 24, 48 and 72 hours after the start of the test
Reference substance (positive control):
yes
Remarks:
potassium dichromate
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:
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:
other: yield
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Details on results:
- No statistically significant effects (p ≤ 0.05) on growth rate and yield of Desmodesmus subspicatus were observed
- Exponential growth in the control (for algal test): yes
Results with reference substance (positive control):
- The reference item potassium dichromate is routinely tested at concentrations of 0.13, 0.25, 0.5, 1.0 and 2.0 mg a.i./L in a separate study.
- ErC50: 1.01 mg/L
- EyC50: 0.38 mg/L
- NOEC: 0.13 mg/L
Reported statistics and error estimates:
NOEC / LOEC calculation for average specific growth rate after 72 hours (based on nominal test item concentrations) were performed using the STUDENT-t test for Homogeneous Variances.

The mean measured concentrations of the substance in the test solutions remained at 91% of nominal values at the start of the test and at 89% at the end of the test (after 72 h). Therefore the toxicity results are based on the nominal concentrations.

Validity criteria fulfilled:
yes

Description of key information

ErC50 (72 h) > 100 mg/L (Desmodesmus subspicatus; OECD 201)

NOErC (72 h) >= 100 mg/L (Desmodesmus subspicatus; OECD 201)

Key value for chemical safety assessment

Additional information

One study is available on the toxicity of Reaction mass of 2-(3,4-dimethyl-1H-pyrazol-1-yl)succinic acid and 2-(4,5-dimethyl-1H-pyrazol-1-yl)succinic acid to algae. The study was conducted as a limit test according to OECD Guideline 201 and GLP (Juckeland, 2012). The test organism Desmodesmus subspicatus was exposed to the test substance at a nominal concentration of 100 mg/L for 72 hours. No statistically significant effect on growth rate and yield was observed during the study. The NOEC is thus determined to be >= 100 mg/L and the EC50 > 100 mg/L.