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Ecotoxicological information

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:
12 - 14 Jun 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions: The study is not performed under GLP conditions. No test substance monitoring is performed. No NOEC value is determined.
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
no NOEC value is calculated
GLP compliance:
no
Remarks:
but performed according to ISO 17025
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Method: Test solutions are prepared in accordance with the OECD monography n°23. Aqueous algae test medium is saturated with the substance to be tested by dynamic contact setting with a known test substance amount. The preparation consists of 68 h of gentle agitation by magnetic stirring to obtain a vortex of about 1/3 (or less under some conditions) of the height between the top and the bottom of the flask, followed by 4 h of phase separation.The aqueous phase, containing the soluble substances is taken to perform the test. The test solution is identified to its loading rate (massic proportion of substance to be tested/ test medium mass introduced into the diphasic reactor) while operating the Water accomodated fraction (WAF). The implemented loaded ratio is : 0.11/1000.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Source: Microbiotests Inc., Venecoweg 19, 9810 Nazareth, Belgium (Batch No.: SC110112)
- Method of cultivation: The algae are maintained in culture in the laboratory by weekly subcultures.

ACCLIMATION
- Acclimation period: An inoculum is prepared by dispersion of algae into dilution water. The cell culture is acclimated for 4 days.
- Culturing media and conditions: same as test
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
23 ± 2 °C
pH:
8.0 - 8.1
Nominal and measured concentrations:
Nominal: 110 mg/L loading rate WAF
Details on test conditions:
TEST SYSTEM
- Test vessel: culture vial for spectrophotometric measurement
- Type: The vials are half-covered.
- Material: polyacrylate; Size: 35 mL
- Initial cells density: 5000 - 10000 cells/mL (confirmed by optical counting)
- Control end cells density: 395531 cells/ml (mean)
- No. of vessels per concentration: 6
- No. of vessels per control: 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to OECD guideline 201
- Culture medium different from test medium: no
- Intervals of water quality measurement: The pH of the control and the treatment is measured at the beginning and the pH of one vial is measured at the end of the test.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: continuous light
- Light intensity and quality: 8000 lux (spectra from 400 - 700 nm)
- The culture vials are placed onto a rotative stirrer (60 mvt/s).

EFFECT PARAMETERS MEASURED: Cell concentration was recorded after 24, 48 and 72 h test duration.
- Determination of cell concentrations: spectrophotometer
- Other: Microscopic examination of algal cells were performed at the end of the test.
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
(WAF)
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
(WAF)
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control: yes
- Observation of abnormalities: No abnormalities were observed.
- Unusual cell shape: The microscopic examination of algae cells, at the end of the test, confirmed the organism identy and the normal shape of the cells (no fading).
- Any stimulation of growth found in any treatment: The growth rate of the treatment was slightly higher than the growth rate of the control.

Table 1: Cell concentrations measured in control and treatment and inhibition in treatment

Nominal concentration [mg/L]

replicate

Measured cell concentration [cells/mL]

Inhibition [%]

24 h

48 h

72 h

control

1

41282

140728

376831

-

2

29638

106910

391650

3

32814

115378

368363

4

32814

130197

413879

5

32814

151368

422347

6

27521

97383

400118

mean

32814

123670

395531

110

1

39165

103029

398707

- 0.2

2

38107

118906

461159

- 1.5

3

55043

134784

419877

- 1.7

4

37048

122082

465393

- 3.9

5

33872

111497

423053

- 4.1

6

34931

112555

475978

- 4.7

mean

39694

117142

440695

-2.7 ± 1.8

Description of key information

No toxic effects up to the limit of water solubility (< 0.15 mg/L) for Pseudokirchneriella subcapitata (OECD 201)

Key value for chemical safety assessment

Additional information

One study investigating toxicity of Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) to freshwater algae is available. The non GLP study was conducted under static conditions according to OECD guideline 201 using Pseudokirchneriella subcapitata as test organism (Bouillon, 2012). A 110 mg/L loading rate WAF was tested in a limit test. No NOEC calculation was performed. No growth inhibition was observed in the treatment throughout the test period of 72 h. Hence, the 72 h-EL10 and EL50 is determined to be > 100 mg/L based on the nominal test concentration.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within the CSR.