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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:
04-03-2013 to 14-05-2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study according to the guideline under GLP
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
Test was performed on water accomodated fraction.
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: duplicate samples from all replicates at all concentrations at 0 and 72 h (pooled in main test)
- Sample storage conditions before analysis: at -20 °C
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: stirring for 23 hours, standing 1 hour and transfer via tube with Nescofilm seal by mid depth syphoning using a glass wool plug (WAF)
- Stirring period: recovery as TOC at 100 mg/L after 24 h stirring 2.67 mg/L; 96 h stirring 2.87 mg/L
- Differential loading: 0.10, 0.32, 1.0, 3.2 and 10 mg/L (all WAFs were prepared by dilution of 10 mg/L WAF)
- Controls: untreated
- Evidence of undissolved material: microscopic evaluation of the WAFs did not show any undissolved material
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchnerella subcapitata
- Strain: CCAP 278/4
- Source : Culture Collection of Algea and Protozoa (CCAP), SAMS Research SErvices Ltd., Scottish Marine Institute, Oban, Argyll, Scotland
- Age of inoculum (at test initiation):
- Method of cultivation: under constant aeration and illumination at 21 °C in AAP medium (pH adjusted to 7.5)

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24 ± 1 °C
pH:
at t=0 7.6-7.7
at t=72 7.9-8.2
Nominal and measured concentrations:
main test
nominal loading rates: 0.10, 0.32, 1.0, 3.2 and 10 mg/L
measured:
t=0 0.119, 0.103, 0.214, 0.687 and 2.13 mg/L;
t=72 measured (TWA): 0.075, 0.067, 0.12, 0.36 and 1.09 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL conical flask with polyurethane foam bug filled with 100 mL
- Aeration: none, sheken at 150 rpm
- Initial cells density: 5E03 cells/mL
- Control end cells density: 5E03 cells/mL (exponential growth observed during the 72 h test period)
- No. of vessels per concentration (replicates): 3 for test substance concentrations
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes AAP

OTHER TEST CONDITIONS
- Adjustment of pH: none
- Photoperiod: continuously light (380-730 nm)
- Light intensity: 7000 Lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Coulter counter at 0, 24, 48 and 72 hours
- Chlorophyll measurement: none

TEST CONCENTRATIONS:
- Range finding study: Loading rates: first 10 and 100 mg/L ; second 0.01, 0.1, and 1.0 mg/L
- Test concentrations:Loading rate: 0.10, 0.32, 1.0, 3.2 and 10 mg/L
- Results used to determine the conditions for the definitive study: inhibition of growth at 1.0 mg/L and above
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
3.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 2.8-3.5 mg/L
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
1.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 0.12 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
dissolved
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
ca. 0.36 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks:
52% inhibition at this concentration
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): yes at 0.1, 0.32 and 1.0 mg/L no abnormalities; at 3.2 and 10 mg/L no intact cells present
Results with reference substance (positive control):
EC50 for potassium dichromate for growth rate 1.2 mg/L
Reported statistics and error estimates:
Bartlett test for homogeneity of variance
Dunnett test for statistically differences between test groups and controls

 Loading rate (mg/L)

Mean Growth Rate (% of controls)

Mean Biomass inhibition (% of controls)

0

100

100

0.10

102

110

0.32

101

105

1.0

98

90

3.2

48

3

10

<0

<0

 

Validity criteria fulfilled:
yes
Conclusions:
The ECr50 for algae is 3.1 mg/L as loading rate. The NOELR is 1.0 mg/L as loading rate (0.12 mg/L measured TWA).
Executive summary:

Algae were exposed to 0, 0.10, 0.32, 1.0, 3.2 and 10 mg/L test substance during 72 hours. Effects on growth rate and biomass were seen at 3.2 and 10 mg/L with no normal cells present at these concentrations. The analyses for accuracy of preparation showed a decrease over the 72 hour test period. The average measured concentration at the NOELR of 1.0 mg/L was 0.12 mg/L.

The ECr50 for algae is 3.1 mg/L as loading rate. The NOEC is considered to be 0.12 mg/L. The ErC50 based on measured concentrations is ca. 0.36 mg/L.

Description of key information

Algae were exposed to 0, 0.10, 0.32, 1.0, 3.2 and 10 mg/L test substance during 72 hours. Effects on growth rate and biomass were seen at 3.2 and 10 mg/L with no normal cells present at these concentrations. The analyses for accuracy of preparation showed a decrease over the 72 hour test period. The average measured concentration at the NOELR of 1.0 mg/L was 0.12 mg/L.

The ELr50 for algae is 3.1 mg/L as loading rate. The NOEC is considered to be 0.12 mg/L. The ErC50 based on measured concentrations is ca. 0.36 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.36 mg/L
EC10 or NOEC for freshwater algae:
0.12 mg/L

Additional information