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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009-07-01 to 2010-06-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: OECD Guideline followed under GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Acetaldehyde
- Substance type: colourless liquid
- Physical state: liquid
- Storage condition of test material: cool in the dark

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
Storage of Samples: All samples were stored in a freezer (= - 10 °C), protected from light until analysis was performed.
Sampling: One sample from the freshly prepared stock solution and duplicate samples from the freshly prepared test media (containing algae) of all test concentrations and from the control were taken at the start of the test.
For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, duplicate samples from the test media of all test concentrations and the control (containing algae) were taken at the end of the test (after the 72 hours test period).
Analyses: The concentrations of the test item were analysed in the duplicate test media samples from all test concentrations and both sampling times (0 and 72 hours). From the control samples only one of the duplicate samples was analysed from each of both sampling times.

Test solutions

Vehicle:
no
Details on test solutions:
The test media of nominal 100 and 50 mg/L were prepared by adding 45, respectively 22.5 µL of the test item directly into 350 mL test water. For the preparation of the lower concentrations, a stock solution of 100 mg test item/L was prepared by adding 45 µl test item into 350 mL test water by intense stirring for 5 minutes. Adequate volumes of this stock solution were diluted with test water to prepare the test media of the desired test concentrations. All media were prepared in closed flasks to avoid volitalisation of the test item. The test media were prepared just before introduction of the algae (= start of the test).

Test organisms

Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Species: Pseudokirchneriella subcapitata, Strain No. 61.81 SAG
Origin: The algae were supplied by the "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen", 37073 Göttingen, Germany.
Breeding Conditions:The algae were cultivated in the laboratories of IBACON under standardised conditions according to the test guidelines.

Study design

Test type:
other: static closed vessel
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h

Test conditions

Hardness:
Calculated water hardness of the test water: 0.24 mmol/L (= 24 mg/L) as CaCO3.

Test temperature:
23°C throughout the test
pH:
The pH was adjusted with e.g. 1 M HCl or 1 M NaOH to pH 8.1 ± 0.1.
8.1 at test start and
8.4 - 8.6 at test end
Dissolved oxygen:
-
Salinity:
-
Nominal and measured concentrations:
Nominal: 100, 50, 25, 12.5 and 6.25 mg test item/L and a control
Details on test conditions:
- Introduction of Algae: The test was started (0 hours) by inoculation of a biomass of 2500 algal cells per mL test medium. These cells were taken from an exponentially growing pre-culture, which was set up 3 days prior to the test start under the same conditions as in the test.
- Replicates:The test was performed with three replicates per test concentration and six replicates in the control. Volumes of approximately 60 mL of algal suspension per replicate were continuously stirred with magnetic stirrers in 50 mL Erlenmeyer flasks. The flasks will be closed with a conical stopper
-Blanks: Additionally, one replicate of each test concentration and of the control was prepared without algae to provide a "blank" for the spectrophotometrical measurements. The additional replicates were incubated under the same conditions as described above. The blank values were subtracted from the absorption measured in the samples containing algae in order to eliminate absorption caused by test item (see also "Determination of the Cell Density").
- Test units: Erlenmeyer flasks of 50 mL volume with approximately 60 mL of test medium and closed with a conical stopper.
- Light Regime: Continuous illumination
- Light Intensity: The light intensity was measured once during the test at x positions distributed over the experimental area at the surface of the test media.
- Mean light intensity: 5847 lux (range: 5560 - 6000 lux)
- The test media will be enriched with 300 mg NaHCO3/L to enable algae growth in closed vessels

Reference substance (positive control):
yes
Remarks:
potassium dichromate

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Biologial details: During the test a stimulating effect on the parameters growth rate and yield occurred in the concentrations of 50 and 100 mg test item/L. However, according to the guidline these stimulating effects are not relevant for the determination of the NOEC and the EC50.

Analytical details: At the start of the test 106 % of the nominal test concentrations were found (average of the test concentrations of nominal 50 and 100 mg test item/L). After 72 hours test duration, 77 % of the nominal values were determined (average of the test concentrations of nominal 50 and 100 mg test item/L). In spite of closed vessel design a part of the test item get lost during the course of the test (e.g. metabolisation, adsorption to the algae). However, since no effect occurred in this algae test and the concentration in the aged test media of nominal 100 mg test item/L (=NOEC) was above 80 %, all reported results refer to nominal concentrations.

Results with reference substance (positive control):
For the evaluation of the quality of the algae and the experimental conditions the reference item potassium dichromate p.a. is tested at least twice a year to demonstrate satisfactory test conditions.
Reported statistics and error estimates:
Based on the calculated cell densities, the 72-hour ErC50 and the 72-hour EyC50 (see Definitions), the corresponding EC10 values and where possible their 95 %-confidence limits were calculated by Probit analysis.
For the determination of the 72-hour LOEC and the 72-hour NOEC, the calculated growth rates, and yields at each test concentration were tested for significant differences compared to the control values by the Williams test (yield and growth rate), respectively.
The software used to perform the statistical analysis was ToxRat Professional, Version 2.10, ToxRat Solutions GmbH, 2009.

Any other information on results incl. tables

Table 1: Fullfillment of the validity criteria

Cell Density
Increase in Control Cultures:


96-fold increase within 72 hours and thus, validity criterion was met.

Coefficient of Variation of Sectional (Daily) Growth Rates in Control Cultures:



17.4 % and thus, validity criterion was met.

Coefficient of Variation of Average Growth between Control Replicates:



3.5 % and thus, validity criterion was met.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Acetaldehyde had no inhibitory effect on algeal growth.
Executive summary:

The influence of Acetaldehyde on the growth of the freshwater green algae Pseudokirchneriella subcapitata was assessed in a static dose-response test in closed vessel design according to OECD Guideline 201. The 72-hour NOEC was determined to be at least 100 mg test item/L. The NOEC might even be higher than this concentration, but concentrations in excess of nominal 100 mg test item/L have not been tested according to the recommendations of the test guidelines. The 72-hour LOEC and the 72-hour EC50 were clearly higher than nominal 100 mg test item/L. These values could not be quantified due to the absence of toxicity of Acetaldehyde up to nominal 100 mg test item/L. During the test a stimulating effect on the parameters growth rate and yield occurred in the concentrations of 50 and 100 mg test item/L.