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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:
2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
- Preparation of the saturated solution: The saturated solution1 (1.00 mg/L test item was weighed out) was prepared with demineralized water two days prior to the start of the exposure (0 h)
- Treatment: The test item was dispersed in the demineralized water by stirring with approximately 1100 rpm for 48 h at room temperature. After
completion of stirring, undissolved particles were removed by centrifugation (1 0 m in, 18533 g).
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- Origin: Sammlung von Algenkulturen (SAG), Pflanzenphysiologisches lnstitut der Universitat Gottingen (Germany), Nikolausberger Weg 18, 37073 Getting en (Germany)
- Cultivation at test facility: Fresh stocks were prepared every month on Z-Agar; Light intensity amounted to 35- 70 IJE · m-2 ·s-1 for 24 h per day.
- Culture medium: Nutrient medium Z according to LOTTGE et al. (1994).
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
0.24 mmol Ca+Mg/L
Test temperature:
21.5-22.5 °C
pH:
8.10-8.20
Salinity:
n.a.
Conductivity:
No data
Nominal and measured concentrations:
Test concentration: 1.0 mg/L (nominal)
No analytical monitoring was carried out since no suitable method for the determination of the test item could be established.
Details on test conditions:
EXPOSURE CONDITIONS:
- Test concentration: The saturated solution was tested in a limit test.
- Control: Six replicates (without test item)
- Reference item: Potassium dichromate is tested twice a year as reference item
- Replicates: Six replicates for the limit concentration and the control
- Test container: Sterile Erlenmeyer flasks, volume: 250 ml, sealed with cotton wool plugs.
- Test volume: 100 ml
- Dilution water: According to the guideline
- Preculture: A three day old preculture, prepared in dilution water, was used as inoculum. For the start of the exposure the preculture was directly
pipetted into the saturated solution and the control.
- Initial cell density: Nominal: approximately 2 - 5 x 103 cells/mL; Current: 4998 cells/mL

BIOLOGICAL PARAMETERS:
- Type and frequency of measurement: Cell density was measured daily via Chlorophyll-a-fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as background signal.
- Self fluorescence: No self-fluorescence was found in the definitive test after 0 hours at the saturated solution.
- Microscope evaluation: Microscopic evaluation of the cells at the start and end of the exposure was carried out. The cells were checked for unusual cell
shapes, colour differences, differences in chloroplast morphology, flocculation, adherence of algae to test containers and agglutination of algae cells.

PHYSICO-CHEMICAL PROPERTIES:
- The pH-value at the start of the exposure was measured in one additional replicate of the limit concentration level and the control.
- At the end of the exposure it was measured from pooled replicates per limit concentration level and control, respectively.
- The room temperature was measured continuously.
- Light intensity was measured prior to the start of the exposure.

EQUIPMENT:
- pH-Meter, pH 191 (WTW)
- Hygro-thermograph (KLIMATHERM)
- Quantum sensor SKP 217 (SKYE INSTRUMENTS L TO.)
- Microplate Reader Chameleon V (HIDEX) with software
- Micro Win 4.41, MIKROTEC LABORSYSTEME GMBH for determination of the cell density
- Shaker, SM 25 A (BOHLER)
- Magnetic stirrer, RH basic 2 (IKA®-WERKE GMBH CO. KG)
- Light microscope (ZEISS Lab 16)
- Fluorescent tubes, OSRAM L 36 W/11-865, cool daylight (test),
- OSRAM L 30 W/840, cool white energy saver (culture)
- Piston Stroke Pipettes (THERMO SCIENTIFIC, BRANDT)
- Analytical balance, LE26P-OCE (SARTORIUS)
- Balance, PLS 1200-3A (KERN)
Reference substance (positive control):
yes
Remarks:
potassium dichromate (SIGMA, batch number MKBH9127V, purity 99.9 %, CAS RN 7778-50-9)
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 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.:
1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Results with reference substance (positive control):
- Growth Rate Inhibition: 72 h-EC50 0.586 mg/L
- Yield Inhibition: 72 h-EC50 0.401 mg/L
Validity criteria fulfilled:
yes
Remarks:
Increase of the cell growth in Exponentially (150 fold); Mean coefficients of variation for section-by-section specific growth rates (13.8%); Coefficient of variation of average specific growth rates (2.77%)
Conclusions:
After 72 hours of exposure no toxic effect (NOEC (reproduction): 1mg/L, ErC 50: > 1 mg/L) against algae at the limit of water solubility. The results are expressed in terms of nominal concentrations.
Executive summary:

The toxicity of Solvent Violet 59 to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 (2011). The study was conducted under static conditions with an initial cell density of 4998 cells/ml. A

saturated solution1 with a nominal concentration of 1 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. No analytical determination was carried out since no suitable method for the determination of the test item could be established. No toxic effect (NOEC (reproduction): 1mg/L, ErC 50: > 1 mg/L) against algae at the limit of water solubility under exposure conditions. The results are expressed in terms of nominal concentrations.

This toxicity study is classified acceptable and satisfies the guideline requirement for algae.

Description of key information

After 72 hours of exposure no toxic effect (NOEC (reproduction): 1mg/L, ErC 50: > 1 mg/L) against algae at the limit of water solubility. The results are expressed in terms of nominal concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 mg/L
EC10 or NOEC for freshwater algae:
1 mg/L

Additional information

"Should read: 72 h EC50: >1 mg/L"