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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
Study period:
27th June 2017 - 30th June 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Remarks:
Certificate attached in the Study report
Specific details on test material used for the study:
Because the test item is very poorly soluble in water, test solutions were prepared using a saturated solution method (water accommodated fraction, WAF) according to the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, OECD No. 23
Analytical monitoring:
not specified
Details on sampling:
The exposure time was 72 hours. The test was started (0 hours) by inoculation of a biomass of approximately 104 algal cells per mL test medium.
Details on test solutions:
Reconstituted algal growth medium (OECD medium, according to OECD 201) was used as dilution water for both the range finding and definitive tests.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Strain number: 61.81 SAG (identical strains: CCAP 278/4; UTEX 1648; ATCC 22662). The algae were supplied by the SAG: Collection of Algal Cultures, Inst. Plant Physiology, and University of Göttingen, GERMANY. Cultured under standardised conditions (see OECD 201) in the Ecotoxicological Laboratory of CiToxLAB Hungary Ltd. The species of Pseudokirchneriella subcapitata used, being a fast-growing species, is convenient for culturing and testing and is a recommended species by relevant guidelines.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
The cell numbers were determined at 24, 48 and 72 hours after starting the test.
Hardness:
Reconstituted algal growth medium (OECD medium, according to OECD 201)
Test temperature:
Culture temperature was checked at the beginning of the experiment and each day thereafter in a flask filled with water, in the climatic chamber. In addition, water temperature was continuously measured (with a min/max thermometer) within the climate chamber. The temperature was in the range of 22.7 – 23.0 °C measured in the flask and between 22.2 and 23.1 °C measured within the climate chamber.
pH:
The pH was checked at the beginning and at the end of the test, in the control and each concentration. The pH of the control medium was not increased by more than 1.5 units during the test. The range of the pH was 7.37 – 9.21 during the experiment.
Dissolved oxygen:
not measured
Salinity:
not measured
Conductivity:
not measured
Nominal and measured concentrations:
nominal loading rates of 6.25, 12.5, 25, 50 and 100 mg/L.
Details on test conditions:
The test was performed with three replicates per test concentration and six replicates in the control group. Volumes of 100 mL algal suspension per replicate in 250 mL Erlenmeyer flasks were continuously shaken by a laboratory orbital shaker to keep algae in suspension. The flasks were covered with air-permeable stoppers.
Reference substance (positive control):
yes
Remarks:
Preliminary Range Finding Test
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
ca. 76.63 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
ca. 12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
LOELR
Effect conc.:
ca. 25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Details on results:
The biological results are based on nominal loading rates (water accommodated fractions, WAFs).The nominal concentrations of test item used in the main experiment were: 6.25, 12.5, 25, 50 and 100 mg/L nominal loading rate WAF.
Results with reference substance (positive control):
Potassium dichromate is tested at least twice a year to demonstrate satisfactory test conditions.
The 72h ErC 50: 0.88 mg/L, (95 % confidence limits: 0.81 – 0.96 mg/L)
The 72h EyC 50: 0.54 mg/L, (95 % confidence limits: 0.50 – 0.59 mg/L)
The 72h EbC 50: 0.64 mg/L, (95 % confidence limits: 0.59 – 0.70 mg/L)
These values are within the range of laboratory ring test data (see ISO Guideline No. 8692).
Reported statistics and error estimates:
The mean coefficient of variation for section-by-section specific growth rates (days 0-1; 1-2; 2-3) in the control cultures was 10.72 %.
The coefficient of variation of average specific growth rates during the whole test period (day 0-3) in the control cultures was 0.78 %.
Validity criteria fulfilled:
yes
Conclusions:
With respect to the inhibitory effect of the test item, the 0-72 h average specific growth rates, areas and yield were significantly different from that of the control group in the examined concentration range of 25.0 – 100.0 mg/L nominal loading rates (WAFs), therefore the NOELR was determined as 12.5 mg/L nominal loading rate and LOELR was determined as 25.0 mg/L nominal loading rate.
Executive summary:

The effect of test item was assessed on algal growth using the unicellular green alga Pseudokirchneriella subcapitata (Selenastrum capricornutum), over an exposure period of 72 hours. The nominal concentrations of test item used in the main experiment were: 6.25, 12.5, 25, 50 and 100 mg/L nominal loading rate WAF. All validity criteria were met, therefore the study can be considered as valid. the NOELR was determined as 12.5 mg/L nominal loading rate and LOELR was determined as 25.0 mg/L nominal loading rate.

Description of key information

The effect of test item was assessed on algal growth using the unicellular green alga Pseudokirchneriella subcapitata (Selenastrum capricornutum), over an exposure period of 72 hours. The nominal concentrations of test item used in the main experiment were: 6.25, 12.5, 25, 50 and 100 mg/L nominal loading rate WAF. All validity criteria were met, therefore the study can be considered as valid. the NOELR was determined as 12.5 mg/L nominal loading rate and LOELR was determined as 25.0 mg/L nominal loading rate.

Key value for chemical safety assessment

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