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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:
2006
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP guideline study, data originate in part from a secondary source
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: control and 100 mg/L. Samples were taken after 0 and 72 hours.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test solutions were prepared by adding the test substance in nutrient medium.Test concentrations of 100, 45, 21 and 9 mg/L were prepared in 2 L beakers by adding the test substance of 100, 45, 21 and 9 mg in 1L of sterile nutrient medium, respectively.The test concentration of 4 mg/L was prepared by diluting the test solution of 9 mg/L.Total volume of 150 ml was used as a final test solution considering necessary amount for the analysis of the test substance in the test solution.The sterile nutrient medium not including test substance was used for a control.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: Strain No. ATCC 22662; UTEX 1648
- Source (laboratory, culture collection): The test species was obtained from American Type Culture Collection (12301 Parklawn Drive, Rockville, Maryland 20852) in March 3, 1994 and cultured at Korea Institute of Toxicology, KRICT.

ACCLIMATION
- Culturing media and conditions: An OECD culture medium was diluted to produce the biomass of 1×104 cells/mL and then sub-cultured continuously at intervals of 3 to 4 days. For pre-cultivation, the test algae were inoculated into the OECD culture medium at a biomass of 0.5-1.0×104 cells/mL 2 to 4 days prior to study initiation.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23.1 ℃
pH:
test start: 7.50 - 8.34
test termination: 8.03 – 9.08
Nominal and measured concentrations:
Nominal test substance concentrations: control, 0.3, 1, 3.1, 9.8, 31.3, and 100 mg/L
Measured test concentrations at 0 h: 0.08-0.88 mg/L
Measured test concentrations at 72 h: 0.61-1.56 mg/L
Details on test conditions:
TEST SYSTEM
- Initial cells density: 1.0×10^4 cells/mL (2-4 days prior to test initiation)
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1


GROWTH MEDIUM
- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD culture medium


OTHER TEST CONDITIONS
- Light intensity and quality: 4,440-8,880 Lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Morphological changes of algal cells were observed including expansion, aggregation, atrophy, and decoloration at 72 hours after exposure. The cell densities were determined by direct counts using ×200 or ×400 microscope (Leica MPS 32)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study
- Test concentrations: control, 0.1, 1, 10, and 100 mg/L.
- Results used to determine the conditions for the definitive study: tthe average specific growth rate was inhibited by 13.5% and by 51.4% for the area under growth curve method at the highest dose of 100 mg/L.
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1.56 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Algal cells were observed to maintain a similar shape to the control in all test solutions. In all the test concentrations, the growth rates of algal cells were higher than those of the control. Therefore, it was determined that the test substance would cause growth stimulation rather than growth inhibition.

Table 1. Growth rates

Nominal concentration

(mg/L)

Growth

rate

Relative

growth rate

(%)

Relative

Inhibition

(%)

Control

0.058

-

-

4

0.072

126

-26

9

0.063

110

-10

21

0.072

125

-25

45

0.069

120

-20

100

0.070

122

-22

Description of key information

Tricalcium bis(orthophosphate) is not acutely toxic to aquatic algae.

Key value for chemical safety assessment

Additional information

The acute toxicity of tricalcium bis(orthophosphate) to aquatic algae was investigated in a study following OECD guideline 201 (Kim et al. 2013). Pseudokirchnerella subcapitata was exposed to nominal test substance concentrations of 0.3, 1, 3.1, 9.8, 31.3, and100 mg/L. The mean measured test concentrations after 72 hours was 0.61-1.56 mg/L. Based on the algal growth rate an EC50(72 h) >1.56 mg/L (measured) was determined (nominal: EC50(72 h) >100 mg/L). Based on the study results tricalcium bis(orthophosphate) is considered not acutely toxic to aquatic algae.