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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Mar 2000
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: According to OECD guideline under GLP
Cross-referenceopen allclose all
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study

Data source

Materials and methods

Test guideline
according to guideline
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
Not relevant
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): Methoxyestradien-Cyanhydrin
- Analytical purity: 91.3%
- Lot/batch No.: 57046805

Sampling and analysis

Analytical monitoring:

Test solutions


Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Study design

Test type:
Water media type:
Limit test:
Total exposure duration:
72 h

Results and discussion

Effect concentrationsopen allclose all
72 h
Dose descriptor:
Effect conc.:
0.086 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
Remarks on result:
other: 0.079 - 0.093
72 h
Dose descriptor:
Effect conc.:
0.115 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 0.106 - 0.126

Any other information on results incl. tables

Table 1: Inhibition of biomass and the growth rate (%) of Scenedesmus subspicatus after 72 h exposure to ZK74834

Inhibition in percent
 Dilution of ZK74834    Concentration of ZK74834 (mg/L)   Biomass (integral)   Growth rate  
0  0,0 (control)   0 0
 1:64    0,0181 )   -5,77 -0,87
 1:32    0,0371 )   4,81 1,62
 1 :16    0,0731 )   39,03 15,63
 1:8    0,1471 )   85,04 70,39
 1:4    0,2941 )   77,64 60,19
 1:2    0,5871 )   76,36 53,77

Applicant's summary and conclusion

Validity criteria fulfilled:
ZK74834 had a concentration-depended inhibitory effect on the growth of Scenedesmus
subspicatus. The EbC50 (biomass) was 0.086 mg/L [95% confidence limits: 0.079 - 0.093], the ErC50 (growth rate) was 0.115 mg/L
[95% confidence limits: 0.106 - 0.126] on the basis of measured concentrations.
Consequently, ZK74834 is very toxic to the green algae Scenedesmus subspicatus.
Executive summary:

The purpose of the study was to determine the effects of Methoxyestradien-Cyanhydrin (ZK74834) on the growth of the green algae Scenedesmus subspicatus. ZK74834 is an intermediate of the synthesis of Gestonorone. The study was conducted in agreement with the test guidelines OECD-Guideline 201.

The test item was incubated in an aqueous solution including nutrients with an algae population of Scenedesmus subspicatus for a test duration of approximately 72 hours. The nutrient solution was made up according to the guidelines. For the preparation of the test solutions a suspension with a nominal loading of 100 mg/L ZK74834 was stirred for 24 hours. This suspension was filtered through a membrane filter (0.45 ~m). The resulting solution served as the saturated solution. It was further diluted for concentration levels of 1 :2, 1 :4, 1 :8, 1 :16, 1 :32 and 1 :64 with nutrient solution. The organic carbon concentration of the saturated solution was analysed with a DOC analyzer at the start and end of the incubation. The test item concentration was calculated on the basis of the molecular formula. The mean measured concentration of the saturated stock solution was determined with 1.17 mg/L. The further test concentrations were extrapolated from the result of the DOC-analysis and are shown in the table below.

As a parameter for the growth of the algae population, the cell density of the test and control solutions were measured via Chlorophyll-a-f1uorescence, excitation at 435 nm, emission 685 nm. Out of the f1uorescence values cell density values were calculated according to a calibration curve. The increase of biomass and the growth rate were calculated on the basis of the cell density. The calculated biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated.