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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:
2000-06-27 to 2000-06-30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Reference:
Composition 1
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Analytical monitoring:
yes
Details on sampling:
Analysis of all test concentrations plus a control; additional analysis of the highest and the lowest test concentration without algal inoculum, at test start and after 72 hours of exposure. HPLC analysis
Vehicle:
no
Details on test solutions:
Method: direct weighing into water from a stock solution (2.4 mg/L)
To produce the stock solution, the test substance was weighed into water, treated for 60 seconds at 8000 rpm with an ultra turrax and afterwards, stirred for 24 hours on a magnetic stirrer. To remove undissolved particles, the resulting emulsion was filtered using a folded filter of the pore size 7 - 12 µm.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- Strain: Chodat
- Source: Institute of Plant Physiology, University of Göttingen, Germany
- Method of cultivation: in a light chamber at 23 +- 2 °C and with a quantum flux which equals to 120 µE/m²*s
- Water for dilution: deionized water
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
no post observation period
Hardness:
no data
Test temperature:
no data
pH:
- at the start of the test: 8.1-8.2
- at the end of the test (after 72h of exposure): see Table 2
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
- Nominal test concentrations: 0.031, 0.063, 0.13, 0.25, 0.5, and 1.0 mg/L
- Measured test concentrations: see Table 1
- Concentrations were also measured in the lowest and highest test concentration at 0 and 72h in replicates without algae, to be able to see if substance adsorbs to algae
Details on test conditions:
- Incoulum: algal suspension taken from an exponentially growing preculture which serves to adjust an initial cell density of 10 000 cells per millilitre - Control: Inoculum in nutrient medium and water for dilution (deionized water)

TEST SYSTEM
- Test vessels: Erlenmeyer flasks (300 mL) with stoppers
- Initial cells density: 10,000 cells/mL
- Control end cells density: inoculum in nutrient medium and water for dilution (deionized water)
- No. of organisms per vessel: no data
- No. of vessels per concentration (replicates): no data
- No. of vessels per control (replicates): no data
- No. of vessels per vehicle control (replicates): no data

GROWTH MEDIUM
- Standard medium used: no data

TEST MEDIUM
- Volume of test medium: 100 mL

Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 0.2 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 0.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 0.06 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: cell density
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
ca. 0.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: cell density
Details on results:
It was shown that the low recovery of the test substance in the replicates can be mainly attributed to adsorption to algae as the replicates without algae did not show a significant loss of substance over 72h. Nevertheless the biological results were based on the arithmetic mean of measured values.
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
no data

Table 3: Determined ECx-values for the test substance

EC-values

Based on biomass (EbC)

(confidence interval)

Based on growthrate (ErC)*

EC05

0.02 (0.00-0.05)

0.02

EC10

0.03 (0.00-0.06

0.03

EC50

0.10 (0.03-0.25)

0.20

EC90

0.39 (0.18-11)

1.3

EC95

0.58 (0.24-41)

2.1

* no data given for the confidence interval

Table 4: Study evaluation after 72 hours of exposure

Nominal concentration test substance [mg/L]

Growth

[integral of biomass]

% inhibition [-] or % increase [+] of growth compared to the control

Growth rate [1/d]

% inhibition [-] or increase [+] of growth rate compared to the control

control

328,000

0.0

1.1

0.0

0.031

310,000

5.5

1.1

0.0

0.063

299,000

8.8

1.1

0.0

0.13

97,400

70.3

0.8

27.3

0.25

35,000

89.3

0.4

63.6

0.5

28,300

91.4

0.3

72.7

1.0

25,000

92.4

0.2

81.8

Validity criteria fulfilled:
yes
Conclusions:
Under the experimental conditions used in the test, the test substance causes an 50 % reduction in growth (of biomass) and in the growth rate of the tested algae species (Scenedesmus suspicatus CHODAT) in a concentration of 0.10 mg/L and 0.20 mg/L respectively. The lowest concentration which causes reduction of the growth in the tested algae species compared to the control within a 72-h-exposure period (=LOEC) was determined as 0.10 mg/L, whereas the highest concentration not causing growth inhibition (=NOEC) was determined as 0.06 mg/L.
Executive summary:

Exponentially-growing cultures of a species of green algae were exposed to six different concentrations of the test substance over several generations under defined conditions. The test solutions were incubated for a period of 72 h, during which the cell density in each vessel was measured every 24 h. The inhibition of growth and growth rate in relation to a control was determined after 72 h after exposure to the test substance. The concentrations of the test substance which cause a 50 % reduction in growth (EbC50) and growth rate (ErC50) relative to control were determined with 0.10 mg/L and 0.20 mg/L respectively. The lowest concentration which causes reduction of the growth in the tested algae species compared to the control within a 72-h exposure period (=LOEC) was determined as 0.10 mg/L, whereas the highest concentration not causing growth inhibition (=NOEC) was determined as 0.06 mg/L.

Description of key information

The 72h ErC50 value is 0.2 mg/L. The 72h NOEC value was determined to be 0.06 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
0.2 mg/L
EC10, LC10 or NOEC for freshwater algae:
0.06 mg/L

Additional information

The key study was performed with the freshwater green algal species Scenedesmus subspicatus according to EU Method C.3 (1992) in a 72 -hour static test. Six nominal concentrations of 0.031, 0.063, 0.13, 0.25, 0.5 and 1 mg/L were tested. Test concentrations were measured at the beginning and end of the test. Results were based on the arithmetic mean of analytical values. Measurements of replicates without algae showed that the substance loss can be mainly attributed to adsorption to algae.

The test substance concentration which caused a 50% reduction in biomass (EbC50) and growth rate (ErC50) relative to control were determined at 0.10 mg/L and 0.20 mg/L, respectively. The lowest concentration which causes reduction of the growth in the tested algae species compared to the control within the 72-h-exposure period (=LOEC) was determined at 0.10 mg/L, whereas the concentration not causing growth inhibition (=NOEC) was determined to be 0.06 mg/L.

The second study probably conducted according to OECD 201 but as only a results page is available and thus no details on the study are available the reliability of the study could not be assessed, and therefore a reliability level of 4 (not assignable) was given to the study. Nevertheless the study supports the findings in the key study. The 72h-NOEC was determined to be 0.13 mg/L and the EC50(72h) was determined to be 0.34 and 0.5 mg/L, respectively.

The effects of the test substance on the growth of marine algae were not studied.