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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
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
- 100 mg of the test item was weighed into a glass flask and mixed with 1000 mL of the test medium.
- After a thorough mixing the stock mixture was not homogeneous with visible not dissolved parts of the test item.
- Therefore, the stock mixture was sonicated with heating at 40°C for 20 min and then mixed by mechanic shaker at room temperature for 24 h.
- Once more the stock mixture was sonicated with heating at 40°C for 20 min and then mixed by mechanic shaker at room temperature for 48 h (total time of mixing was 72 h).
- The homogeneous and transparent stock solution of yellow colour and characteristic odour was the highest test concentration and was used to prepare the lower test concentrations by sequential dilution with the test medium.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata (Reinsch) Korshikov (syn. Selenastrum capricornutum Prinz)
- Strain: SAG 61.81
- Source (laboratory, culture collection): cultured in the Institute of Industrial Organic Chemistry Branch Pszczyna, Department of Ecotoxicology, Laboratory of Aquatic Toxicology, stock from The Algae Collection of Göttingen University, Germany
- Age of inoculum (at test initiation): A pre-culture with cell density of 1 x 10*4 per mL was renewed three days before the definitive test.
- Method of cultivation: Algae were transferred from agar bevels to the fresh medium (for Pseudokirchneriella subcapitata AAP medium is recommended in 250 mL Erlenmeyer flask and incubated in 21 – 24 °C in constant illumination (pre-culture). The algae culture was renewed (inoculated to a
new medium) twice a week in sterile conditions.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21.9 – 22.7 ºC
pH:
exposure initiation: 7.33 - 8.44
exposure termination: 7.66 - 8.05
Nominal and measured concentrations:
Nominal test concentrations: control, 0.032, 0.1, 0.32, 1.0, 3.2, 10, 32 and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: glass flasks
- Size, fill volume: 250 mL, 100 mL
- Renewal rate of test solution: The algae culture was renewed (inoculated to a new medium) twice a week in sterile conditions. A pre-culture with cell density of 1 x 10*4 per mL was renewed three days before the definitive test.
- Initial cells density: 1 x 10*4cells/mL
- Control end cells density: 1 x 10*4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Photoperiod: constant illumination
- Light intensity and quality: 6600 – 7990 lx, six 24 W light bulbs

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: microscopic cells counting in Bűrker chamber

Reference substance (positive control):
yes
Remarks:
3,5 dichlorophenol
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.117 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.116 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
10.27 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
2.138 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
In samples of fresh solutions the concentration of the test item was in the range of 84.6 – 95.0% of nominal

In samples of old solutions with algae the determined concentration of the test item in the concentrations < 32 mg/L were below the LoD (< 0.03 mg/L), and 36.0 and 55.5% of the initial concentration in the concentrations 32 and 100 mg/L

The test item concentration was not stable under test conditions and the decrease was concentration-dependent
Results with reference substance (positive control):
The ErC50 (72h) of the control substance was 2.09 mg/L.
Reported statistics and error estimates:
Shapiro-Wilk’s Test on Normal Distribution, Levene’s Test on Variance Homogeneity (with Residuals), Welch-t test for inhomogenous variances

Increase of biomass in the control during 72 h was 91.2 fold (criterion – not less than 16 fold).

The coefficient of variation of the mean specific growth rate among the replicates in the control over the whole test period (test initiation – test termination) was 0.9% (criterion – not more than 7%).

The mean of the replicate coefficients of variation in the section-by-section growth rate was 12.5% (criterion – not exceeding 35%).

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of aquatic algae was investigated for ‘α,α'-propylenedinitrilodi-o-cresol’ in a GLP guideline study according to the OECD 201 (Alga, Growth Inhibition Test).

The analytical monitored study was conducted with the green algae species Pseudokirchnerella subcapitata.

After 72 hours of exposure the ErC50 was 1.117 mg/L and the ErC10 was 0.116 mg/L (measured).

Description of key information

Acutely toxic to aquatic algae.


The toxicity of aquatic algae to the substances was investigated in a GLP guideline study according to OECD 201 (Algae, Growth Inhibition Test).. The analytical monitored study was conducted with the green algae species Pseudokirchnerella subcapitata.

After 72 hours of exposure, the ErC50 was 1.117 mg/l and the ErC10 was 0.116 mg/l (measured).

Key value for chemical safety assessment

EC50 for freshwater algae:
1.117 mg/L
EC10 or NOEC for freshwater algae:
0.116 mg/L

Additional information

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