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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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2S,3S,4S,5R,6R)-6-[(2R,3R,4R,5R,6R)-3-acetamido-2,5-dihydroxy-6-sulfooxyoxan-4-yl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid

Molecular formula:

(C14H19Na2NO14S)n

IUPAC Name:

2S,3S,4S,5R,6R)-6-[(2R,3R,4R,5R,6R)-3-acetamido-2,5-dihydroxy-6-sulfooxyoxan-4-yl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid

Sampling and analysis

Analytical monitoring:

yes

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

Source: The algae were supplied by the SAG: Collection of Algal Cultures, Inst. Plant Physiology, and University of Göttingen, GERMANY. Cultured under standardised conditions (see OECD 201) in the Ecotoxicological Laboratory of Citoxlab Hungary Ltd.

Justification of species: The species of Pseudokirchneriella subcapitata used, being a fast-growing species, is convenient for culturing and testing and is a recommended species by relevant guidelines.

Breeding conditions: Stock cultures are small algal colonies that are inoculated onto agar regularly. These are transferred to fresh agar medium at least once every two months and are maintained under standardised conditions according to the test guidelines.
The pre-culture is intended to give a quantity of algae suitable for the inoculation of test cultures. The pre-culture was prepared with the OECD algal growth medium, incubated under the same conditions as the test and used when still growing exponentially, after an incubation period of four days. When the algal cultures contain deformed or abnormal cells, they were discarded.

Study design

Total exposure duration:

72 h

Test conditions

Test temperature:

Culture temperature was checked at the beginning of the experiment and each day thereafter in a flask filled with water, in the climatic chamber. In addition, water temperature was continuously measured (with a min/max thermometer) within the climate chamber. The temperature was 22.6-22.7°C measured in the flask and 21.0-22.8 °C measured within the climate chamber.

pH:

The pH was checked at the beginning and at the end of the test, in the control and each concentration. The pH of the control medium was not increased by more than 1.5 units during the test. The range of the pH was 7.45 – 8.91 during the experiment.

Details on test conditions:

The algal culture flasks were continuously illuminated. The light intensity at the position occupied by algal culture flasks during the test was about 7773 lux (equivalent to ~105 µE/m2/s), which was ensured with fluorescent lamps (with a spectral range of 400-700 nm). The differences in light intensity between the test vessels did not exceed  15 % and therefore provided equal conditions for each test vessel.

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

other: ErLR50

Remarks:

the calculated concentration/loading rate of Test Item which results in a 50 % reduction of growth rate (μ) relative to the control

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

other: EbLR50

Remarks:

the calculated concentration/loading rate of Test Item which results in a 50 % reduction of biomass (b) relative to the control

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

other: EyLR50

Remarks:

the calculated concentration/loading rate of Test Item which results in a 50 % reduction of yield (y) relative to the control

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Effect concentrations 4

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Effect concentrations 5

Key result

Duration:

72 h

Dose descriptor:

LOELR

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

In conclusion, under the conditions of this study, the Test Item had no toxic effect at saturation; the ELR50 results and the LOELR are higher than the solubility level of the Test Item in the test medium.

The 72h EbLR50 value: > 100 mg/L nominal loading rate WAF
The 72h ErLR50 value: > 100 mg/L nominal loading rate WAF
The 72h EyLR50 value: > 100 mg/L nominal loading rate WAF
The 72h NOELR value: 100 mg/L nominal loading rate WAF
The 72h LOELR value: > 100 mg/L nominal loading rate WAF

Executive summary:

The effect of the Test Item was assessed on algal growth using the unicellular green alga Pseudokirchneriella subcapitata (Selenastrum capricornutum), over an exposure period of 72 hours.

 

As no toxicity was observed in the preliminary concentration range-finding test, therefore 100 mg/L Test Item nominal loading rate (WAF)and one control was usedin the main test.

The concentration of the total carbon content was analytically determined at the start and at the end of the experiment. The biological results are based on the nominal concentration.

 

The test design included 6 replicates at test concentration and 6 replicates for the untreated control.

Statistical comparisons of biomass, average specific growth rates and yield in control and in treated groups were carried out using 2 Sample t-Test (a= 0.05) by TOXSTAT software.

TheE_rLR_50,E_bLR₅₀and E_yLR₅₀values of the Test Item were determined directly from the raw data.

The 72h E_bLR₅₀value:     >100 mg/L nominal loading rateWAF

The 72h E_rLR₅₀value:      >100 mg/L nominal loading rateWAF

The 72h E_yLR₅₀value:     >100 mg/L nominal loading rateWAF

The72hNOELR:             100 mg/L nominal loading rateWAF

The72hLOELR:             >100 mg/L nominal loading rateWAF

 

In conclusion, under the conditions of this study, the Test Item had no toxic effect at saturation; the ELR₅₀ results and the LOELR are higher than the solubility level of the Test Item in the test medium.