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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2005
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study; restriction due to lack of analytical measurement of test material (nominal concentration used)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Report Date:
2005

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
1) OECD 2000. Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures
2) ECETOC 1996. Aquatic Toxicity Testing of Sparingly Soluble, Volatile and Unstable Substances
- Evidence of undissolved material (e.g. precipitate, surface film, etc): At zero hours all control and test cultures were clear colorless solutions

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Green alga
- Strain: Scenedesmus subspicatus, strain CCAP 276/20
- Source (laboratory, culture collection): Liquid cultures were obtained from the Culture Collection of Algae and Protozoa (CCAP) Institute of Freshwater Ecology, The Ferry House, Far Sawrey, Ambleside, Cumbria.

- Method of cultivation: Cultures were maintained in the laboratory at a temperature of 21 degrees C under continuous illumination (intensity approximately 7000 lux) and constant aeration.

Study design

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

Test conditions

Test temperature:
Temperature was maintained at 24C throughout the test
pH:
pH at 0 hours in control and test material solutions ranged from 6.8 to 7.7. pH values at 72 hours in control and test material solutions ranged from 6.9 to 8.4.
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL glass conical flasks were used. Three flasks each containing 100 mL of test preparations were used for the control and each treatment group. The flasks were plugged with polyurethane foam bungs and incubated at 24 C under continuous illumination (intensity approximately 7000 lux) and constantly shaken at approximately 150 rpm for 72 hours.

- Initial cells density: Preculture conditions gave an algal suspension in log phase growth characterized by a cell density of 1.68 x106 cells per mL. Inoculation of test medium gave an initial cell density of 10^4 cells per mL.

- Control end cells density:
Mean cell density of control at 0 hours was 7.52X10^3 cells per mL
Mean cell density of control at 72 hours was 5.74 x10^5 cells per mL

- No. of vessels per concentration (replicates): triplicate
- No. of vessels per control (replicates): triplicate

GROWTH MEDIUM
The culture medium used for the range finding and definitive tests was the same as that used to maintain the stock culture. Stock solutions of the culture medium was prepared using reverse osmosis purified deionized water. The culture medium contained the following macronutrients: NaNO3, MgCl2.6H2O, CaCl2.2H2O, MgSO4.7H2O, K2HPO4, NaHCO3. The culture medium contained the following micronutrients: H3BO3, MnCl2.4H2O, ZnCl2, FeCl3.6H2O, CoCl2.6H2O, Na2MoO4.2H2O, CuCl2*2H2O; Na2EDTA.2H2O, Na2SeO3.5H2O

- Standard medium used: yes

OTHER TEST CONDITIONS
- Light intensity and quality: 7000 lux continuous illumination

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
Samples were taken at 1, 24, 48, and 72 hours and the cell densities determined using a Coulter Multisizer II Particle Counter.

TEST CONCENTRATIONS

The loading rates to be used in the definitive test were determined by a preliminary range finding test. The range finding test was conducted by exposing Scenedesmus subspicatus cells to a series of nominal loading rates of 10, 100, and 1000 mg/L for a period of 72 hours. After addition of the test material, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a slight dimple at the water surface. These were stirred for 24 hours. The stirring was stopped and the mixtures allowed to stand for 1 hour. Microscopic observations made on the WAFs indicated that dispersed test material was present in the water column and hence it was considered justifiable to remove the undissolved material by filtering through a glass wool plug (2-4 cm in length). Microscopic observations of the WAFs performed after filtering showed that there were no globules/microdispersions of test material to be present.

The cell densities and percentage inhibition of growth values from the exposure of the alga to the test material during the range finding test showed no effect on growth at 10 mg/L loading rate WAF, however growth was observed to be reduced at 100 and 1000 mg/L loading rate WAFs. Based on this information loading rates of 10, 20, 40, 80, and 160 mg/L were selected for the definitive test.















Reference substance (positive control):
no

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
21 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 20 - 22 mg/L
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
24 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 22 - 26 mg/L
Details on results:
- Exponential growth in the control (for algal test): yes

- Observation of abnormalities (for algal test): All test and control cultures were inspected microscopically at 72 hours. After 72 hours there were no abnormalities detected in the control or test cultures at 10 and 20 mg/L loading rate WAFs; however no intact cells were observed to be present in the test cultures at 40, 80, and 160 mg/L loading rate WAF.

Any other information on results incl. tables

Table. Inhibition of Growth Rate and Biomass

Nominal Loading Rate (mg/L)

Area Under Curve at 72 h

% Inhibition

Growth Rate

(0-72 h)

% Inhibition

Control

1.09E7

--

0.060

--

10

1.23E7

[13, increase vs controls]

0.056

7

20

6.84E6

37

0.047

22

40

-3.97E5

104

-0.022

137

80

-4.88E5

104

-0.028

147

160

-5.88E5

105

-0.046

177

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Exposure of Scenedesmus subspicatus to the test material gave an EbL50 (72h) value of 21 mg/L loading rate WAF and an ErL50 (0-72hr) value of 24 mg/L loading rate WAF. The No Observed Effect Loading rate was 10 mg/L loading rate WAF.
Executive summary:

Introduction. A study was performed to assess the effect of the test material on the growth of the green alga Scenedesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No. 201, “Alga Growth Inhibition Test”. 

 

Methods:

Following a preliminary range finding test, the alga were exposed to Water Accommodated Fractions of test material over a range of nominal loading rates of 10, 20, 40, 80, and 160 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 degrees C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group using a Coulter Multisizer Particle Counter.

 

Results:

Exposure ofScenedesmus subspicatusto the test material gave an EbL50 (72h) value of 21 mg/L loading rate WAF and an ErL50 (0-72hr) value of 24 mg/L loading rate WAF. The No Observed Effect Loading rate was 10 mg/L loading rate WAF.