isliFe

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19/02/2018 - 19/04/2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch number : TROD7BB06

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The primary stock solution used in the range-finding test was prepared by dissolving 0.0250 g of the test substance in 250 mL with OECD medium, resulting in a concentration of 100 mg/L. The stock solution of 1 mg/L was prepared from dilution of the primary stock solution.
The primary stock solution used in the definitive test was prepared by dissolving 0.1000 g of the test substance in 1000 mL with OECD medium, resulting in a concentration of 100 mg/L. The stock solution of 3.2 mg/L was prepared from dilution of the primary stock solution.
From these initial stock solutions, a series of dilutions was prepared in order to obtain the desired tested concentrations

Test organisms (species):

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

Details on test organisms:

The test system was obtained from Culture Collection of Algae at Goettingen University - SAG 61.81 on October, 08th, 2013, and is recommended by the Guideline OECD 201 (2011).

The stock culture was prepared and maintained under lab-controlled conditions in solid medium with protease peptone. The inoculated solid medium was kept inside a culture room, with controlled temperature of 21 to 24°C and luminosity of 2100 ± 10% lux. After algae cultures reached an ideal growth (about one week), they were maintained at temperature of 2 to 6°C and luminosity of 100 to 200 lux in order to slow down the algae growth.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.2 to 22.5°C

pH:

start: 8.1
end (72 h): 7.4-7.5

Nominal and measured concentrations:

nominal: 0.32, 1, 3.2, 10, 32 and 100 mg/L

Details on test conditions:

Temperature: 22.2 to 22.5°C
Light: 5002 lux (average)
Photoperiod: continuous light
Shaker velocity: 130 rpm (average)
Test duration: 72 hours

The test was performed with three replicates per each concentration and control. One more replicate per concentration was prepared for determinations of pH and chemical analysis. The algae inoculum was transferred aseptically to each test flask, with calculated volume to yield an initial cell concentration of 5 x 103cells.mL.
All test flasks were randomly positioned in an incubating chamber with controlled temperature and kept under continuous shaking and lighting conditions. Every day the flasks were relocated to different places inside the incubating chamber.
The used test flasks were 250 mL glass Erlenmeyer containing 100 mL of test solution. All glassware used in the test was washed with detergent, commercial acetone, 5% nitric acid and rinsed thoroughly with tap water and followed with deionized water.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

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.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Details on results:

The EyC50 72 hours for the test substance, obtained in this study with Pseudokirchneriella subcapitata, was not determined because in the highest test concentration (100 mg.L-1) it caused 31% inhibition of algal growth, so the value of the EyC50 72 hours was greater than 100 mg.L-1. The highest concentration of the test substance in which no statistically significant adverse effect was observed in the 72-hour period was 10 mg.L-1 and the lowest
concentration of the test substance in which an adverse effect was observed statistically significant (CEO) was 32 mg.L-1. The ErC50 72 hours for the test substance MEAHA-Fe was not determined because at the highest test concentration (100 mg.L-1) it caused 7% inhibition of algal growth, so the value of the ErC50 72 hours was greater than 100 mg.L-1.

Results with reference substance (positive control):

The 72-hours EyC50 value of the reference substance potassium dichromate was 0.71 mg.L-1 (confidence limits at 95% = 0.65 to 0.78 mg.L-1), demonstrating that the toxic sensitivity of the algae was within the accepted range (ISO, 1989), which report toxicity ranged between 0.60 and 1.03 mg.L-1.

Validity criteria fulfilled:

yes

Conclusions:

The 72-hours EyC50 value for alga Pseudokirchneriella subcapitata exposed to MEAHA-Fe was not determined because the highest tested concentration (100 mg/L) caused only 31% of the inhibition in the algae growth, therefore, the 72-hours EyC50 value was greater than 100 mg/L.
The highest test substance concentration with no observed significant adverse effect (NOEC) on algal growth was 10 mg/L and the lowest test substance concentration at which was observed significant reducing effect on growth (LOEC) was 32 mg/L. The 72-hours ErC50 and ErC10 values were not determined because the highest tested concentration (100 mg/L caused only 7% of the inhibition in the algae growth, therefore, the 72-hours ErC50 and ErC10 values were greater than 100 mg/L.

Executive summary:

The objective of this study was to evaluate the toxicity of MEAHA-Fe on alga Pseudokirchneriella subcapitata. A range-finding test was conducted to find the concentrations that cause algae growth inhibition. Based on the results of the range-finding test, a definitive test was carried out with the following concentrations of test substance: 0 (control); 0.32; 1; 3.2; 10; 32 and 100 mg/L. The test was incubated during 72 hours inside chambers with controlled conditions of luminosity, temperature, and agitation. The

72-hours EyC50 value was not determined, because the highest dose tested (100 mg/L) caused 31% inhibition of algal growth, so that EyC50 72 hours was greater than 100 mg/L. The 72 hr ErC50 and ErC10 values were not determined because at the highest test concentration (100 mg/L) it caused only 7% inhibition of algal growth, so the ErC50 and ErC10 72 hours were higher than 100 mg/L. The highest test substance concentration which no observed significant adverse effect (NOEC) on algal growth was 10 mg/L and the lowest test substance concentration at which was observed significant reducing effect on growth (LOEC) was 32 mg/L.

Description of key information

The 72-hours EyC50 value for alga Pseudokirchneriella subcapitata exposed to MEAHA-Fe was not determined because the highest tested concentration (100 mg/L) caused only 31% of the inhibition in the algae growth, therefore, the 72-hours EyC50 value was greater than 100 mg/L.

The highest test substance concentration with no observed significant adverse effect (NOEC) on algal growth was 10 mg/L and the lowest test substance concentration at which was observed significant reducing effect on growth (LOEC) was 32 mg/L. The 72-hours ErC50 value was not

determined because the highest tested concentration (100 mg/L caused only 7% of the inhibition in the algae growth, therefore, the 72-hours ErC50 value was greater than 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

10 mg/L