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Toxicity to aquatic algae and cyanobacteria

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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)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The test item concentrations were analytically determined from of each dilution level and the control after 0 h (test start) and 72 h (test end). Separate replicates for test item analysis after 0 h were prepared without algae. SampIes at end of the test were taken directly from the test replicates.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A definitive test with the saturated solution was carried out. 100 mg/L of the test item were directly weighed out, freshly prepared with dilution water and shaken with 20 rpm for 24 h at room temperature in brown glass flask. After a separation phase of 1.5 h the saturated solution was taken from the homogenous liquid phase. The saturated solution and further four dilution levels were tested in a geometrical series with a dilution factor of 10, nominal.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: green alga
- Strain: SAG 86.81
- Source: Collection of algal cultures in Goettingen, Germany
- Cultivation at test facility: Fresh stocks ware prepared every month on Z-Agar. Light intensity amounted to 35 - 70 µE/m2s for 24 h per day
- Culture medium: Nutrient medium Z according to LÜTTGE et al. (1994)

PRECULTURE
A four day old preculture was used as inoculum. lncubation was performed in 500 ml Erlenmeyer flasks with dilution water. For the start of the test the preculture was directly pipetted into each dilution level and the control to receive an initial cell concentration of approximately 2 – 5E+03 cells/ml in the replicates.

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21 - 24 °C
pH:
6.9 - 8.3
Nominal and measured concentrations:
Nominal test concentrations: 1, 3.2, 10, 32, 100% of the saturated solution
Mean measued concentrations: 0.0642, 0.174, 0.915, 2.97 and 6.30 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: sterile Erlenmeyer flasks sealed with cotton wool plugs, 250 mL, 100 mL
- Initial cells density: 2- 5 E+03 cells/mL

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD 201 medium
- Intervals of water quality measurement: pH at study initiation and study end, temperature continuously, light intensity prior test start

OTHER TEST CONDITIONS
- Photoperiod:24 h/d light
- Light intensity and quality: 60 - 120 µE/m2s

EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: after 72 h in the concentration levels 2.97 and 6.3 mg/L with a plankton chamber
- Chlorophyll measurement: chlorophyll-a-fluorescence, excitation at 436 nm, emission at 685 nm

Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.297 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.242 - 0.359 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.215 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.182 - 0.289 mg/L
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.254 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% CL: 0.230 - 0.277 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.194 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 95% CL: 0.179-0.213 mg/L
Details on results:
After 72 h algae were transferred from geometric mean measured concentrations of 0.915 - 6.30 mg/L and the control to fresh untreated medium and allowed to grow tor further 4 - 12 days under test conditions. The test item effect was observed to be reversible at these concentrations. Therefore, there is potential for recovery following exposure up to 6.30 mg/L (highest test concentration).
Results with reference substance (positive control):
ErC50 = 0.695 mg/L
EyC50 = 0.320 mg/L

ADDITIONAL REPORTED EFFECT CONCENTRATIONS

72 -h ErC20: 0.239 mg/L (95% CL: 0.202 -0.308 mg/L)

72 -h EyC20: 0.209 mg/L (95% CL: 0.192 -0.229 mg/L)

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
See 'Attached justification'
Reason / purpose:
read-across source
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.297 mg/L
Remarks on result:
other: as determined from read-across to C13 alcohol, branched
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.215 mg/L
Remarks on result:
other: as determined from read-across to C13 alcohol, branched

Description of key information

Key value for chemical safety assessment

Additional information

For algae toxicity a study is available for C13 branched alcohol (CAS 27458 -92 -0). The study is performed according to OECD TG 201 and in compliance with GLP criteria (Evonik Oxeno, 2009). In this study, freshwater green algae (D. subspicatus) were exposed to a range of isotridecanol concentrations for 72 -h. Test solution were prepared by adding 100 mg/L of the test item to dilution water followed by shaking (24 hours) at room temperature in a brown glass flask. After a separation phase of 1.5 hours, the saturated solution was further diluted to obtain nominal test concentrations of 0 (control), 3.2, 10, 32 and 100% of saturated solution. Presence of test substance was analytically verified and measured concentrations determined to be 0.0642, 0.174, 0.915, 2.97 and 6.30 mg/L. Cell concentrations were determined after 72 hours exposure in the concentration levels 2.97 and 6.3 mg/L and yield and growth rate calculated from these data. Form this study the 72 -h EC50 and EC10 values for growth rate were 0.297 and 0.215 mg/L, respectively. For yield, the 72 -EC50 and EC10 values were determined at 0.254 and 0.194 mg/L, respectively. After the 72 -hour exposure period algae from the control and the three highest test concentrations were transferred to fresh untreated medium and allowed to grow for a further 4 -12 days under conditions identical to the 72 -h exposure period. The test item effect was observed to be reversible at these concentrations and thus there is potential for recovery following exposure up to 6.30 mg/L.