Toxicity to aquatic algae and cyanobacteria.005

Toxicity to aquatic algae and cyanobacteria.005

Administrative data

Purpose flag:

weight of evidence

Study result type:

experimental result

Study period:

31 May 2010 until 3 June 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

Well conducted study according to standard guideline and GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report Date:

2010

Materials and methods

Test guideline

Qualifier:

according to

Guideline:

ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum)

Deviations:

no

GLP compliance:

yes

Test materials

Identity of test material same as for substance defined in section 1 (if not read-across):

no

Test material identity

Identifier:

CAS number

Identity:

7775-09-9

Details on test material:

Sample labelling: Reach sample 0043
Batch number: 20001809
Expiry date:7/3/2010
Appearance: White powder
Purity: 99.7 ± 0.6%
Date received: 27 April 2010
Storage conditions: In darkness at room temperature
Expiry date: Expiry date:7/3/2010

Analytical monitoring:

yes

Details on sampling:

Samples were taken at the start of the test before addition of the algae and at the end of the test.

Vehicle:

no

Details on test solutions:

A solution of the test material in seawater (1000 mg/l) was prepared by dissolving overnight with a magnet stirrer. The solution was further diluted in test medium to obtain the selected exposure concentrations.

Test organisms

Test organisms (species):

Skeletonema costatum

Details on test organisms:

Strain: NIVA strain BAC 1
Source: NIVA culture collection
Stock culture: Cultured in natural seawater with 10 % Z8 medium on reciprocating shaker and continuous light at approximately 20 °C.
Inoculation culture: The inoculum was taken from a culture in ISO 10253 growth medium prepared from natural sea water with salinity 33 PSU.

Study design

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

20.6 - 21.4 °C

pH:

7.85 - 8.92

Nominal and measured concentrations:

Sample nominal Measured Sodium Chlorate % of nominal
10 mg/l initial 5.1 51
10 mg/l end 4.3 43
22 mg/l initial 16.8 77
22 mg/l end 15.6 71
46 mg/l initial 37 81
46 mg/l end 36 78
100 mg/l initial 98 98
100 mg/l end 96 96
220 mg/l initial 211 96
220 mg/l end 198 90
460 mg/l initial 455 99
460 mg/l end 430 93
1000 mg/l initial 995 100
1000 mg/l end 944 94

Details on test conditions:

TEST SYSTEM
- Test vessel: 30 ml glass vials, covered with plastic film. The culture volume was approximately 12 ml.
- Initial cells density: 5*10E6 cells/l
- Control end cells density: 1.23*10E9 cells/l
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes, ISO 10253 medium, prepared from filtered natural seawater

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: collected from 60 m depth in the Oslofjord
- Culture medium different from test medium: No


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous light
- Light intensity and quality: 68 μM m-2 s-1.
- Salinity (for marine algae):

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Coulter Multisizer electronic particle counter with a 100 μ orifice tube

Reference substance (positive control):

yes

Results and discussion

Effect concentrationsopen allclose all

Effect concentrations 1

Duration:

72 h

Endpoint:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Endpoint:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Reported statistics and error estimates:

Dunnett's test

Any other information on results incl. tables:

Mean cell density (10E6 cells/l) and calculated growth rates (d-1) after 72 hours

Concentration SODIUM CHLORATE	start	24 hours	49 hours	72 hours	0-72 h μ (d-1)
Control	5	45	322	1234	1.8
10 mg/l	5	50	367	1467	1.9
22 mg/l	5	47	370	1190	1.8
46 mg/l	5	46	358	1490	1.9
100 mg/l	5	45	321	1317	1.9
220 mg/l	5	45	334	1491	1.9
460 mg/l	5	45	340	1507	1.9
1000 mg/l	5	40	292	1215	1.8

Applicant's summary and conclusion

Conclusions:

The study is well conducted according to standard guideline, with chemical ananlysis and GLP.
Sodium chlorate is not toxic to the marine algae Skeletonema costatum. The NOEC is equal to or greater than 1000 mg/l.

Executive summary:

The inhibitory effect of Sodium Chlorate on the growth of the marine diatom Skeletonema costatum, strain NIVA BAC1, has been investigated. The test was performed according to ISO 10253: Marine algal growth inhibition test with Skeletonema costatum and Phaeodactylum tricornutum. A series of concentrations (10, 22, 46, 100, 220, 460 and 1000 mg/l) of the test material were prepared by dilution of a dispersion of the test material in algal growth medium. The solutions were inoculated with 5*10E6 cells/l of an exponentially growing culture of S. costatum. Three replicates of each concentration were incubated in 30 ml glass vials with 12 ml culture volume on a shaking table at 20 ±1 °C, under continuous illumination. Six replicate cultures in growth medium were used as controls. Growth was monitored by daily counting of cell numbers using a Coulter Multisizer M3. Test concentrations were verified by chemical analysis of chlorate in the test medium at start and end of the test. The test material caused no significant inhibition of the growth of S. costatum at concentrations up to 1000 mg/l. Therefore, NOEC is equal to or greater than 1000 mg/l.

Validity criteria fulfilled:

yes