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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:
2015-2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: well performed OECD study with GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2016
Report Date:
2016

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:
yes
Details on sampling:
Analytical evaluation of the saturated solution of the testitem and the control was carried out via
HPLC-DAD from freshly prepared media after 0 hours. Separate replicates for the test item analysis at the beginning of exposure were prepared without algae. The recovery rates of the test item at the start was below the SysQL. Therefore, no analytical evaluation after 72 h was carried out.

Test solutions

Vehicle:
no
Details on test solutions:
Preparation of the saturated solution
The saturated solution (1.00 mg/L test item were weighed out) was prepared with demineralized water two days prior to the start of the exposure (0 h). The dispersion was stirred for 48 hours (1100 rpm, room temperature) with a magnetic stirrer. Undissolved particles were removed by membrane filtration (membrane filter 0.45 µm, RC, MACHEREY-NAGEL). The filter was saturated in order to avoid adsorption during the filtration. The first 25 mL filtrate were discarded. The filtration was interrupted for ca. 15 minutes to allow for adsorption and saturation of the filter material with dissolved test item. Thereafter, the filtration was continued. The next 25 mL were discarded. After the separation treatment the components of the dilution water were added to the saturated solution. The following filtrate, i.e. the saturated solution, was used in the test. During filtration the filter was always kept covered. 

Test concentration
The saturated solution was tested in a limit test.

Control
Six replicates (without test item) were tested under the same test conditions as the test replicates.

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus subspicatus Chodat
- Strain: SAG 86.81
- Source (laboratory, culture collection): SAG Pflanzenphysiologisches Institut der Universitaet Goettingen, Nikolausberger Weg 18, D-37073 Goettingen, Germany
- Age of inoculum (at test initiation): 4 days
- Method of cultivation: Fresh stocks were prepared every month on Z-Agar. Light intensity amounted to 35 - 70 µE x m-2 x s-1 for 24 h per day.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
No

Test conditions

Hardness:
Dilution water: 0.24 mmol Ca+mg/L.
Test temperature:
min.: 21.5 max.: 22.0, mean value: 21.8
pH:
Nominal concentration pH-value
[mg/L] Start; 0 hours End; 72 hours
1.00 8.02 8.21
Control 7.97 8.23
Dissolved oxygen:
Not measured
Salinity:
Not measured, freshwater conditions
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Type (delete if not applicable): open, cotton wool plugs
- Material, size, headspace, fill volume: sterile 250 mL Erlenmeyer flasks, test volume 100 mL
- Aeration: Test containers were placed on a rotary shaker and oscillated at appr. 70 rpm
- Type of flow-through (e.g. peristaltic or proportional diluter): None
- Renewal rate of test solution (frequency/flow rate): One application at test start
- Initial cells density: Nominal: approximately 2 - 5 x 103 cells/mL, Actual: mean 4847 cells/mL
- Control end cells density: Mean 1390450 cells/mL
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6



GROWTH MEDIUM
- Standard medium used: yes



TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dilution water, composition acc. to the guideline
- Hardness: 0.24 mmol Ca+Mg/L
- pH-value: 8.1 +/- 0.2
- Culture medium: Nutrient Medium Z acc. to LÜTTGE et al. (1994)


OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: 24 h
- Light intensity and quality: 60 - 120 µE x m-2 x s-1, mean value: 68.7



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter] fluorimeter, Cell density and self fluorescence was measured daily via Chlorophyll-a- fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as background signal.



TEST CONCENTRATIONS
- Range finding study:No





Reference substance (positive control):
yes
Remarks:
Potassium dichromate

Results and discussion

Effect concentrations
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1 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
- Observation of abnormalities (for algal test):
- Unusual cell shape: No
- Colour differences: No
- Flocculation: No
- Adherence to test vessels: No
- Aggregation of algal cells: No
- Other: No
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: No
Results with reference substance (positive control):
- Results with reference substance valid? Yes
The toxicity of potassium dichromate (SIGMA, batch number MKBQ9179V, purity 100.0 %, CAS RN 7778-50-9) to the unicellular freshwater green alga Desmodesmus subspicatus was determined over a period of 72 hours from 2015-10-19 to 2015-10-22. For results see Table 8. The reference item toxicity is in the valid range following test facility SOPS.

EC50-Values of the Reference Item
based on nominal concentrations mg/L, (0-72 hours)
Current Study Valid Range (average ± 3 x SD)
Growth Rate Inhibition
ErC50 0.685 0.671 ± 0.401
95 % confidence interval 0.603 - 0.794
Yield Inhibition
EyC50 0.362 0.320 ± 0.139
95 % confidence interval 0.328 - 0.398
SD = Standard deviation



Reported statistics and error estimates:
EC-values and statistical analyses
EC-values of the growth rate and yield inhibition were estimated empirically based on the results of the only treatment level (Limit test design).

NOEC and LOEC values
NOEC/LOEC were determined by calculation of statistical significance of growth rate and yield. As standard a t-test was used for NOEC/LOEC calculations. When running a t-test a Normality test and an Equal Variance test were done first. The SHAPIRO-WILK-Test was used to test for normally distributed populations. The Levene median test was used for equal variance. P-values for both Normality and Equal Variance tests are 0.05. The -value (acceptable probability of incorrectly concluding that there is a difference) is =0.05.


Software
The data for the tables in this report were computer generated and have been rounded for presentation from the full derived data. Consequently, if calculated manually based on the given data minor deviations may occur from these figures.
Calculations were carried out using software
• Excel, MICROSOFT CORPORATION
• SigmaPlot, SPSS INC.

Any other information on results incl. tables

Cell Densities

 

Replicate

Cell density [cells/mL]

No.

0 hours

24 hours

48 hours

72 hours

Saturated solution with a nominal loading of
1 mg/L

1

4847

35692

237579

1445611

2

4847

37241

244669

1272914

3

4847

35090

264710

1544322

4

4847

38044

236251

1498045

5

4847

39516

267587

1539127

6

4847

36105

270733

1475917

Mean

4847

36948

253588

1462656

Control

1

4847

37481

238425

1282487

2

4847

34580

251164

1271423

3

4847

42566

278276

1334729

4

4847

43523

258264

1466103

5

4847

38910

300038

1520510

6

4847

39656

292500

1467450

Mean

4847

39453

269778

1390450

         

 


 

Evaluation after 72 hours

Statistically significant differences of growth rates and yield compared to control values are marked (+), not significant differences are marked (-).

 

 

Replicate

Growth rate

Inhibition of growth rate

Yield

Inhibition of yield

No.

[d-1]

[%]

[cells/mL]

[%]

Saturated solution with a nominal loading of 1 mg/L

1

 

1.90

-1

 

1440764

-4

2

 

1.86

2

 

1268067

8

3

 

1.92

-2

 

1539475

-11

4

 

1.91

-1

 

1493198

-8

5

 

1.92

-2

 

1534280

-11

6

 

1.91

-1

 

1471070

-6

Mean

(-)

1.90

-1

(-)

1457809

-5

Control

1

 

1.86

 

 

1277640

 

2

 

1.86

 

 

1266576

 

3

 

1.87

 

 

1329882

 

4

 

1.90

 

 

1461256

 

5

 

1.92

 

 

1515663

 

6

 

1.90

 

 

1462603

 

Mean

 

1.89

 

 

1385603

 

 

 

Section-by-Section and Average Specific Growth Ratesof the Control Group (0 – 72 hours)

 

 

Replicate No.

Specific growth rate [d-1]

Mean

(0 - 72 h)

SD

±

CV
[%]

Mean CV [%]

section-by-section                           

0 - 24 hours

24 - 48 hours

48 - 72 hours

Control

1

2.05

1.85

1.68

1.86

0.182

9.77

12.8

2

1.97

1.98

1.62

1.86

0.204

11.0

3

2.17

1.88

1.57

1.87

0.302

16.1

4

2.20

1.78

1.74

1.90

0.253

13.3

5

2.08

2.04

1.62

1.92

0.255

13.3

6

2.10

2.00

1.61

1.90

0.258

13.5

 

 

 

Mean

1.89

 

 

 

 

 

SD ±

0.03

 

 

 

 

CV [%]

1.37

 

CV= Coefficient of variation

SD= Standard deviation

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
In this study the test item was found not to inhibit the growth rate of the freshwater green alga Desmodesmus subspicatus after 72 hours. The NOEC-value of the test item for both inhibition of growth rate and inhibition of yield after 72 hours was 1.00 mg/L. The EC50-values of the test item for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were both > 1.00 mg/L, respectively. All effect levels are given based on the saturated solution prepared with a nominal loading of 1 mg/L of the test item.
Executive summary:

The toxicity of the test item to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 (2011) and Council Regulation (EC) No.761/2009/Method C.3 (2009) . The aim of the study was to assess the effects on growth rate and yield over a period of 72 hours.

The study was conducted under static conditions with an initial cell density of 4847 cells/mL.Asaturated solutionwith a nominal concentration of 1.00 mg/L was tested. Six replicates were tested for the limit concentration and the control. Environmental conditions were determined to be within the acceptable limits.

The concentrations of the test item in the saturated solution and the control were analytically verified via HPLC-DAD at the start of exposure. The recovery rates ofthe test item at the start were below the System Quantifiquation Limit of the analytical method (0.1 mg/L test item).

All effect values of the test item are given based on the nominal concentration.

 

Table1:  NOEC, LOEC, EC - values of the test item (0-72 hours)

                  based on the saturated solution, prepared with 1 mg/L

                               

 

Growth Rate Inhibition

NOEC

  1.00

LOEC

> 1.00

ErC10

> 1.00

ErC20

> 1.00

ErC50

> 1.00

 

Inhibition of Yield

NOEC

  1.00

LOEC

> 1.00

EyC10

> 1.00

EyC20

> 1.00

EyC50

> 1.00