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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions (no purity)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1994
Report Date:
1994

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct dispersion in culture medium. A 640 mg/L stock solution was prepared in culture medium and serial dilutions produced the required test concentrations.

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Green algae
- Strain: CCAP 276/20

Study design

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

Test conditions

Test temperature:
24 °C
pH:
at test start 8.0
at test end 7.5 - 10.3
Dissolved oxygen:
Medium was air-saturated at test start.
Nominal and measured concentrations:
Nominal: 20, 40, 80, 160 and 320 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: conical flasks
- Type (delete if not applicable): closed (loosely stoppered)
- Material, size, headspace, fill volume: size: 250 mL, fill volume: 100 mL
- Shaking: Orbital shaker, 100 rpm
- Initial cells density of control: 2.17E04 cells/mL
- Control end cells density: 7.99E05 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes, AAP medium according to guideline

- Intervals of water quality measurement: pH of each vessel was measured at test start and test end

OTHER TEST CONDITIONS
- Photoperiod: continuous light
- Light intensity and quality: approx. 7000 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Cell densities were determined at 0, 24, 48 and 72 h.
- Determination of cell concentrations: Cell counting using a Haemocytometer

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2x

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
86 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
75 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.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes
- The results of the test solution analysis showed an increasing carbon concentration with increasing nominal test concentration. The results also showed that there was no significant change in carbon concentration observed over the 72 h exposure period and this was taken to demonstrate the stability of the test preparations employed during the period of exposure.

OBSERVATION OF ABNORMALITIES
- Colour differences: Colourless cells at 160 and 320 mg/L
- Aggregation of algal cells: yes, at 160 and 320 mg/L
- Observation of pH-shift: The pH values of the control and test cultures changed from 8.0 at test start to 7.5 to 10.3 at test end. This effect is considered to be due to the large numbers of algal cells in the log phase of growth respiring oxygen and producing carbonates and bicarbonates as part of photosynthesis which in solution give alkaline conditions. This effect is not considered to affect the integrity of the study given that the cell density of the control cultures increased by a factor 03 37 during the test.

Reported statistics and error estimates:
Statistical analysis using a Students t-test was carried out on the area under the growth curve data for the control and all test concentrations. There were no statistically significant differences (P ≥ 0.05) between the control and 20 mg/L test concentration, however all other test concentrations were significantly different (P < 0.05), and therefore the NOEC is given as 20 mg/L.

Any other information on results incl. tables

Table 1: Inhibition of Growth from the Exposure of S. subspicatus to the test substance for 72 h

Nominal Concentration (mg/L)

Area under curve at 72 h

% Inhibition

Growth rate (0-24 h)

% Inhibition

Control

1.70E07

-

0.051

-

20

1.72E07

+1

0.053

+4

40

1.37E07

19

0.043

16

80

9.18E06

46

0.019

63

160

4.79E05

97

0.000

100

320

-7.64E04

100

-0.005

110

Table 2: Results from Total Organic Carbon (TOC) Analysis

Samples

Nominal Concentration (mg/L)

Concentration of TOC corrected for control (mg C/L)

0 h

20

11.75

40

24.19

80

50.21

160

100.95

320

194.65

72 h

20

10.30

40

21.66

80

46.11

160

86.60

320

191.37

Applicant's summary and conclusion