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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:
from 2000-08-18 to 2000-09-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
EEC, Directive 92/69/1992
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Details on sampling:
- Sampling: after 24, 48, or 72 hours
Vehicle:
no
Details on test solutions:
The test medium (reconstituted water and test item) was freshly prepared. The calibrated flask with test item and vehicle, reconstituted water, was treated in an ultrasound bath for 1 hour. Subsequently, the preparation was stirred with a magnetic stirrer for further 23 hours. Afterwards, the preparation was filtered through a filter funnel with a pore size of 10 - 16 µm. The filtrate was used for the study.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: green unicellular algae
- Strain: SAG 86.81
- Source (laboratory, culture collection): "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universitat Gottingen"
- Method of cultivation: Prior to start the study, the algae were grown in reconstituted water as preculture and the growth rate was determined.

ACCLIMATION
- Acclimation period: none
- Culturing media and conditions (same as test or not):the same
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
250 mg CaCO3
Test temperature:
22 - 23 °C
pH:
7.81 - 9.74
Nominal and measured concentrations:
Nominal concentration of 100 mg/L (limit test); due to very the low water solubility and the fact that the study was a limit test, no further analysis was initiated.
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type: open - completely sealed with sterilized stoppers
- Material, size, headspace, fill volume: glass, 300 mL, 100 mL fill volume
- Aeration: none
- Initial cells density: 10000 algae cells/mL
- Control end cells density: 1188540 cells/mL
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1

GROWTH MEDIUM
- Standard medium used: yes, reconstitution water prepared according to the guideline

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: same as the growth medium

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuously illuminated
- Light intensity and quality: 7500 to 9500 Lux

EFFECT PARAMETERS MEASURED
- Determination of cell concentrations:The algae cell densities were determined with an electronic particle counter (Coulter, Z2).

TEST CONCENTRATIONS
- Justification for using less concentrations than requested by guideline: In a pretest under static conditions, inhibition of the growth rate of the algae, Desmodesmus subspicatus, was not observed at a concentration of 100 mg/L nominally.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
Regularly, a positive control test to check the test system is carried out with potassium dichromate.

Table 1: Cell density

 

Cell density per mL

Growth
inhibition

(0 - 72 hours)

nominal

 

0 hour

24 hours

48 hours

72 hours

Ia

Iµt

0

 

10000

51030

241791

1230633

 

 

 

10000

54927

257040

1228527

 

 

 

10000

52740

242420

1106460

 

 

 

mean

10000

52899

247084

1188540

 

 

100

 

10000

59130

319209

1268460

 

 

 

10000

58473

333251

1280610

 

 

 

10000

60210

324411

1260117

 

 

 

mean

10000

59271

325624

1269729

 

 

Inhibition Ia

 

-14.9

-30.3

-11.3

-14.4

-1.4

Ia = inhibition of cell growth in percent

Iµt = Inhibition of growth rate in percent

-Ia = The growth of the algae was better in the test medium than in the control group.

A dose group with nominal 100 mg/L of the test item (maximal water solubility < 0 005 mg/L) revealed no aquatic toxicity in this test system.

An aqueous solution of nominal 100 mg/L of the test item revealed no effect for Desmodesmus subspicatus. The EC50 exceeded the maximal water solubility (< 0.005 mg/L) of the test material and. thus, could not determined in this test.

The following ECx values and no effect concentration for Desmodesmus subspicatus were determined:

72 h EbC50 = > 0.005 mg/L (nominal > 100 mg/L)

72 h ErC50 = > 0.005 mg/L (nominal > 100 mg/L)

NOEC = > 0 005 mg/L (nominal > 100 mg/L)

Validity criteria fulfilled:
yes
Conclusions:
The test item was tested to Desmodesmus subspicatus in an open static test system according to OECD 201 (1984). Under the given conditions of this study the 72-h ErC50 value and the 72-h NOEC were determined to be > 100 mg/L.
Executive summary:

The influence of the test substance on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested according to OECD 201 (1984) under GLP conditions. The study design included one control and one test item group with three replicates, each containing about 100 mL reconstituted water or test medium and 10000 cells/mL at the start of the experimental phase. The algae were exposed to a filtrate of nominal 100 mg/L and the study was performed as a limit test in an open static test system. The analysis of the saturated aqueous preparation revealed that the water solubility of the test substance in reconstituted water was < 0.005 mg/L and could not be determined analytically. The test material concentration in the aqueous medium could not be quantified since it was below the level of detection. Regularly, a positive control test to check the test system is carried out with potassium dichromate. The validity criteria of the test were met. Under the given conditions of this study the 72-h ErC50 value and the 72-h NOEC were determined to be > 100 mg/L.

Description of key information

The test item was tested to Desmodesmus subspicatus in an open static test system according to OECD 201 (1984). Under the given conditions of this study the 72-h ErC50 value and the 72-h NOEC were determined to be > 100 mg/L.

Key value for chemical safety assessment

Additional information

The influence of the test substance on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested according to OECD 201 (1984) under GLP conditions. The study design included one control and one test item group with three replicates, each containing about 100 mL reconstituted water or test medium and 10000 cells/mL at the start of the experimental phase. The algae were exposed to a filtrate of nominal 100 mg/L and the study was performed as a limit test in an open static test system. The analysis of the saturated aqueous preparation revealed that the water solubility of the test substance in reconstituted water was < 0.005 mg/L and could not be determined analytically. The test material concentration in the aqueous medium could not be quantified since it was below the level of detection. Regularly, a positive control test to check the test system is carried out with potassium dichromate. The validity criteria of the test were met. Under the given conditions of this study the 72-h ErC50 value and the 72-h NOEC were determined to be > 100 mg/L (reference 6.1.5-1).