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Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-04-09 to 2019-04-12

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)

Version / remarks:

2011

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

All concentration levels and the control were analytically verified via HPLC-DAD at the start (0 hours) and at the end of the exposure (72 hours) with algae.
Separate replicates for the test item analysis after 0 hours and 72 hours were prepared in the original test vessels with algae at the start of the exposure. The replicates for test end were incubated under test conditions until analysis.

Vehicle:

no

Details on test solutions:

A stock solution with 100 mg test item/L was freshly prepared with dilution water. The dispersion was agitated until the solution was visually clear. Out of the stock solution 6 concentrations were test in a geometrical series with a dilution factor of 3.16. The dilution levels were based on the results of a preliminary range finding test.

Test organisms (species):

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

Details on test organisms:

Origin: Culture Collection of Algae and Protozoa (CCAP) SAMS Research Services Ltd Dunstaffnage Marine Laboratory Dunbeg, OBAN; Argyll PA37 1QA; Scotland, UK
Cultivation at test facility: Fresh stocks are prepared every month on Z-Agar. Light intensity amounts 2567 - 5130 lux for 24 hours per day.
Culture medium: Nutrient medium Z according to Lüttge et al. (1994)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

0.24 mmol Ca+Mg/L

Test temperature:

21.5-22.5 °C

pH:

0 hours: 8.0-8.08; 72 hours: 8.0-8.94

Dissolved oxygen:

Measurement is not necessary

Nominal and measured concentrations:

Nominal concentrations: 0.316 - 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L;
Measured concentrations (geometric mean): 0.253 - 0.776 - 2.29 - 7.81 - 27.0 - 89.3 mg/L

Details on test conditions:

Static condition in a closed system without headspace

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

6.68 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

32.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

< 0.253 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

< 0.253 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

yield

Details on results:

See table 1

Results with reference substance (positive control):

With Headspace
72h-ErC50 = 0.701 mg/L (valid range: 0.743 ± 0.616 mg/L)
72h-EyC50 = 0.353 mg/L (valid range: 0.407 ± 0.308 mg/L)

Without Headspace
72h-ErC50 = 0.244 mg/L (valid range: 0.743 ± 0.616 mg/L)
72h-EyC50 = 0.236 mg/L (valid range: 0.407 ± 0.308 mg/L)

Reported statistics and error estimates:

Statistical significance-Growth rate:
Shapiro-Wilk´s Test on normal distribution
Levene´s Test on variance homogeneity
Williams Multiple Sequential t-test Procedure;
Statistical significance-Yield:
Shapiro-Wilk´s Test on normal distribution
Levene´s Test on variance homogeneity
Multiple Sequentially-rejective Welsh- t-test after Bonferroni-Holm

Table 1:Evaluation after 72 hours

Statistically significant differences of growth rates and yield compared to control values are marked (+), not significant differences are marked (-).

Measured concentration [mg/L]	Replicate No.	Growth rate [d-1]	Inhibition of growth rate [%]	Yield	Inhibition of yield [%]
89.3	1	-0.0542	100	-813	100
	2	0.0247	98	416	100
	3	0.0398	97	686	100
	Mean	(+)0.0034	98	(+)96	100
27.0	1	0.836	44	61042	87
	2	0.873	41	68967	85
	3	0.885	41	71577	85
	Mean	(+)0.865	42	(+) 67195	86
7.81	1	1.35	10	301395	36
	2	1.31	12	272260	43
	3	1.30	13	263011	44
	Mean	(+) 1.32	12	(+) 27889	41
2.29	1	1.41	5	370581	22
	2	1.43	5	383603	19
	3	1.44	4	400471	15
	Mean	(+）1.43	4	(+)384885	19
0.776	1	1.36	9	312124	34
	2	1.38	7	337340	29
	3	1.34	10	293431	38
	Mean	(+)1.36	9	(+) 314298	34
0.253	1	1.51	-1	490276	-4
	2	1.39	7	349542	26
	3	1.47	2	422783	8
	Mean	(-) 1.46	3	(-)424534	10
Control	1	1.46		425784
	2	1.51		492744
	3	1.46		424129
	4	1.54		536361
	5	1.53		521222
	6	1.47		440754
	Mean	1.49		473499

 

 

Validity criteria fulfilled:

yes

Conclusions:

The growth inhibition effects of the test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was tested. The 72h-ErC50 and 72h-ErC10 values were determined to be 32.1 mg/L and 6.68 mg/L, respectively.

Executive summary:

The toxic effect of the test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201 and Council Regulation (EC) No. 266/2016 C.3 and GLP. The study was conducted under static conditions over a period of 72 hours. Based on the results of a preliminary study, six concentrations within a range of 0.316-100 mg/L in a geometric series with a separation factor of 3.16 were tested. The green algae with an initial cell density of 5416 cells/mL were exposed to each concentration level and the control (test medium without test item). Three replicates were tested for each test item concentration and six replicates for the control. The concentrations of the test item were analytically verified via HPLC-DAD in fresh media at the start of the exposure and at the end of ex exposure (0 and 72 h). The measured concentrations were not maintained within the range of ±20% of the nominal values, the effect concentrations were given on the basis of the geometric mean measured test item concentrations. The 72h-ErC50 and 72h-ErC10 values were determined to be 32.1 mg/L and 6.68 mg/L, respectively.

Description of key information

The toxic effect of the test item to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201 and Council Regulation (EC) No. 266/2016 C.3 and GLP. The study was conducted under static conditions over a period of 72 hours. Based on the results of a preliminary study, six concentrations within a range of 0.316-100 mg/L in a geometric series with a separation factor of 3.16 were tested. The green algae with an initial cell density of 5416 cells/mL were exposed to each concentration level and the control (test medium without test item). Three replicates were tested for each test item concentration and six replicates for the control. The concentrations of the test item were analytically verified via HPLC-DAD in fresh media at the start of the exposure and at the end of ex exposure (0 and 72 h). The measured concentrations were not maintained within the range of ±20% of the nominal values, the effect concentrations were given on the basis of the geometric mean measured test item concentrations. The 72h-ErC50 and 72h-ErC10 values were determined to be 32.1 mg/L and 6.68 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

32.1 mg/L

EC10 or NOEC for freshwater algae:

6.68 mg/L