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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:
March 2017- March 2018
Reliability:
1 (reliable without restriction)
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: AH03201
- Expiration date of the lot/batch: 01 February 2019
- Purity test date:

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity:
- Specific activity:
- Locations of the label:
- Expiration date of radiochemical substance:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material:
- Stability under test conditions:
- Solubility and stability of the test substance in the solvent/vehicle:
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing:
- Preliminary purification step (if any):
- Final dilution of a dissolved solid, stock liquid or gel:
- Final preparation of a solid:

FORM AS APPLIED IN THE TEST (if different from that of starting material)

TYPE OF BIOCIDE/PESTICIDE FORMULATION (if applicable)

OTHER SPECIFICS:
Analytical monitoring:
yes
Details on sampling:
- Concentrations:
- Sampling method:
- Sample storage conditions before analysis: frozen
Vehicle:
no
Details on test solutions:
Preliminary solubility work conducted indicated that it was not possible to obtain a testable solution of the test item using traditional methods of preparation e.g. ultrasonication and high shear mixing. A preliminary media preparation trial indicated that a dissolved test item concentration of approximately 20 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of this item under test conditions. Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to solutions of the test item at nominal concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution (3 replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ±1 °C. The test item solutions were prepared by stirring an excess (100 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2 μm Sartorius Sartopore filter, first approximate 2 liters discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the remaining test groups. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland.
- Age of inoculum (at test initiation):
- Method of cultivation:

ACCLIMATION
- Acclimation period:
- Culturing media and conditions (same as test or not): same
- Any deformed or abnormal cells observed: no
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24 +/- 1°C
pH:
7.1 to 9.0 (7.1 to 8.5 in the controls)
Dissolved oxygen:
not applicable
Nominal and measured concentrations:
Nominal Concentrations: 10, 3.2, 10, 32, 100 %v/v saturated solution
Geometric Mean Measured Concentrations: 0.11, 0.24, 1.1, 3.7, 17 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL glass conical flasks
- Type (delete if not applicable): open plugged with foam bungs
- Material, size, headspace, fill volume: 100mL
- Aeration: no
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density: 5.00 x 10(3) cells per mL
- Control end cells density:
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates):

GROWTH MEDIUM
- Standard medium used: yes/no
- Detailed composition if non-standard medium was used:

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
- Total organic carbon:
- Particulate matter:
- Metals:
- Pesticides:
- Chlorine:
- Alkalinity:
- Ca/mg ratio:
- Conductivity:
- Culture medium different from test medium:
- Intervals of water quality measurement:

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH:
- Photoperiod:
- Light intensity and quality:
- Salinity (for marine algae):

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement:
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations:
- Results used to determine the conditions for the definitive study:
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.11 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Analysis of the test preparations at 0 hours showed measured test concentrations to range from 0.33 to 24 mg/L. A decline in measured test concentrations was observed after each 24-Hour period in the range of 0.25 to 23 mg/L at 24 hours, less than the limit of quantification (LOQ), determined to be 0.011 mg/L, to 21 mg/L at 48 hours and from less than the LOQ to 1.5 mg/L at 72 hours. Given this decline in measured test concentrations it was considered appropriate to calculate the results based on the geometric mean measured test concentrations in order to give a “worst case” analysis of the data.
Reported statistics and error estimates:
One way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955) was carried out on the growth rate and yield data after 72 hours for the control and all test concentrations to determne any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS, 1999-2001).
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the growth of the green algae, Pseudokirchneriella subcapitata has been investigated over a 72-hr period and based on the geometric mean measured test concentrations, the ErC50 value was estimated to be 2.6 mg/L with a 72-hr NOEC value for growth rate of 0.11 mg.L.
Executive summary:

An algal growth inhibition test was conducted with exposure of MCS-1562 to the green algae, Pseudokirchneriella subcapitata over a 72 -hr exposure period. The study was conducted under GLP and followed OECD 201. Analysis of the test preparations at 0 hours showed measured test concentrations to range from 0.33 to 24 mg/L. A decline in measured test concentrations was observed after each 24-Hour period in the range of 0.25 to 23 mg/L at 24 hours, less than the limit of quantification (LOQ), determined to be 0.011 mg/L, to 21 mg/L at 48 hours and from less than the LOQ to 1.5 mg/L at 72 hours. Given this decline in measured test concentrations it was considered appropriate to calculate the results based on the geometric mean measured concentrations. After 72 -hrs, the geometric mean measured test concentraitons resulted in an ErC50 value of 2.6 mg/L.

Description of key information

An OECD 201 algal growth inhibition test was conducted with exposure of MCS-1562 to the green algae, Pseudokirchneriella subcapitata. The resulting 72 -hr ErC50 value, based on geometric mean measured concentrations was 2.6 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.6 mg/L
EC10 or NOEC for freshwater algae:
0.11 mg/L

Additional information