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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-04-08 until 2015-09-24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2015
Report Date:
2015

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Principles of method if other than guideline:
Not relevant
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

Sampling and analysis

Analytical monitoring:
yes
Remarks:
HPLC/UV
Details on sampling:
Samples were taken from the control and the 100% v/v saturated solution test group from the bulk test preparation at 0 hours and from the pooled replicates at 72 hours for quantitative analysis. All samples were stored frozen prior to analysis.

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION OF TEST SOLUTIONS
In view of the difficulties associated with the evaluation of aquatic toxicity of poorly water soluble test items, a modification of the standard method for the preparation of aqueous media was performed. An approach endorsed by several important regulatory authorities in the EU and elsewhere (ECETOC, 1996 and OECD, 2000; for references see original study report), is to expose organisms to a saturated solution of the test item in cases where the test item is of high purity and is poorly soluble in water and in the permitted auxiliary solvents and surfactants. Using this approach, a saturated solution was prepared by stirring an excess (50 mg/L) of test item in culture medium for a period of 24 hours prior to removing any undissolved test item present by filtration (0.2 µm Sartorius Sartopore, first approximate 1 liter discarded in order to pre-condition the filter) to give a saturated solution of the test item.

Range-finding test concentrations were 0.10, 1.0, 10 and 100% v/v saturated solution.

Based on the results of the range-finding test a "limit test" was conducted at a concentration of 100% v/v saturated solution.

A nominal amount of test item (550 mg) was dispersed in 11 liters of culture medium with the aid of propeller stirring at approximately 1500 rpm for 24 hours. After 24 hours the stirring was stopped and any undissolved test item was removed by filtration through a 0.2 µm Sartorius Sartopore filter (first approximate 1 liter discarded in order to pre-condition the filter) to give a 100% v/v saturated solution. An aliquot (1 liter) of the stock solution was inoculated with 13.4 mL of algal suspension to give the required test concentration of 100% v/v saturated solution.

The stock solution and the prepared concentration were inverted several times to ensure adequate mixing and homogeneity.

Test organisms

Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
The test was carried out using Pseudokirchneriella subcapitata strain CCAP 278/4. Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland.

Master cultures were maintained in the laboratory by the periodic replenishment of culture medium. The master cultures were maintained in the laboratory under constant aeration and constant illumination at 21 ± 1 °C.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
Not applicable

Test conditions

Test temperature:
24 +/- 1 °C
pH:
At 0 h: 7.6-7.7
At 72 h: 8.4
Dissolved oxygen:
no data
Nominal and measured concentrations:
Nominal: 100% v/v saturated solution
Measured:
Reference substance (positive control):
yes
Remarks:
potassium dichromate

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: % v/v saturated solution
Nominal / measured:
nominal
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: % v/v saturated solution
Nominal / measured:
nominal
Basis for effect:
biomass
Results with reference substance (positive control):
Exposure of Pseudokirchneriella subcapitata (CCAP 278/4) to the reference item gave the following results:
ErC50 (0 – 72 h) : 1.0 mg/L; 95% confidence limits 0.90 – 1.2 mg/L
EyC50 (0 – 72 h) : 0.49 mg/L; 95% confidence limits 0.42 – 0.58 mg/L

No Observed Effect Concentration (NOEC) based on growth rate: 0.25 mg/L
No Observed Effect Concentration (NOEC) based on yield: 0.25 mg/L
Lowest Observed Effect Concentration (LOEC) based on growth rate: 0.50 mg/L
Lowest Observed Effect Concentration (LOEC) based on yield: 0.50 mg/L

The results from the positive control with potassium dichromate were within the normal ranges for this reference item.
Reported statistics and error estimates:
Student’s t-test incorporating Bartlett's test for homogeneity of variance (P = 0.05)

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated and gave EC50 values of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution. This study showed that there were no toxic effects at saturation.
Executive summary:

A study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed that described in the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth

Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

Preliminary solubility work conducted indicated that it was not possible to obtain a testable solution of the test item using traditional methods of preparation e.g. ultrasonication and high shear mixing.

A preliminary media preparation trial indicated that a saturated solution method of preparation was appropriate for this test item. Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to a solution of the test item at a nominal concentration of 100% v/v saturated solution (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C. The test item solution was prepared by stirring an excess (50 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2 µm Sartorius Sartopore filter, first approximate 1 liter discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test item.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

Exposure of Pseudokirchneriella subcapitata to the test item gave EC50 values of greater than 100% v/v saturated solution. The No Observed Effect Concentration was determined to be 100% v/v saturated solution. This study showed that there were no toxic effects at saturation.