Gallium trichloride

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Aluminium, gallium, and molybdenum toxicity to the tropical marine microalga Isochrysis galbana.

Author:

Melanie A. Trenfield, Joost W. van Dam, Andrew J. Harford, David Parry, Claire Streten, Karen Gibb and Rick A. van Dam

Year:

2015

Bibliographic source:

Environmental Toxicology and Chemistry, 34: 133-1840

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Triplicate cultures (50 mL in 100-mL Erlenmeyer flasks) of I. galbana (3 103 cells/mL) were exposed to a range of concentrations of Al, Ga, or Mo at 28±1 °C for 72 h. The background concentrations of target metals in the seawater controls were approximately 9µg/L Al, 0.04µg/L Ga, and 11 µg/L Mo. Growth rate (as doublings per day) was calculated as the slope of the linear regression of log10 algal cell concentration versus time. This growth rate (expressed as a percentage of the growth of the control) was used to derive the chronic effect value for growth inhibition. A test was considered valid if the growth rate of control replicates was 2.0 ± 0.4 doublings/d.

GLP compliance:

not specified

Remarks:

Not specified in publication

Test material

Test material information

Constituent 1

Reference substance name:

Gallium trichloride

EC Number:

236-610-0

EC Name:

Gallium trichloride

Cas Number:

13450-90-3

Molecular formula:

Cl3Ga

IUPAC Name:

gallium trichloride

Test material form:

not specified

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

On 2 occasions, 72-h subsamples (200 mL) were also taken and ultrafiltered. These samples were taken from additional flask replicates that did not contain algae but were stored in the same conditions for 72 h alongside algal replicates. The speciation of metals in these solutions may have potentially been modified if algae had been present. Ideally, this trial could be repeated using solutions containing algae, to determine what influence the algae has on the speciation of these metals. Each ultrafiltered sample was accompanied by a sample of the total fraction and the <0.45-mm fraction (Minisart syringe filters; Sartorius). Although precipi- tation was not observed during testing with Ga and Mo, total and ultrafiltered samples were also compared for 1 test with each of these metals.

Test solutions

Vehicle:

not specified

Test organisms

Test organisms (species):

other: Isochrysis galbana (CS-177)

Details on test organisms:

Isochrysis galbana (CS-177) was acquired from the CSIRO Microalgae Supply Service. The commercial Tahitian isolate (also identified as I. galbana affinis) originated from Matieva, Society Islands, French Polynesia.
The culture was maintained in sterilized Guillard’s f2 medium in the laboratory for approximately 2 mo prior to testing at pH 8±0.2, 28±1 °C, and a 12:12-h light:dark cycle (36 W cool white triphosphor lighting, 80–100 mmol photons/m2/s). Cultures (50 mL) were maintained in 100-mL Erlenmeyer flasks and agitated on an orbital shaker at 150 rotations per minute. Each week, 1 mL of a 7-d-old I. galbana culture was transferred to 50 mL of f2 medium under aseptic conditions. Nutrient-rich f2 medium was used to sustain the long-term health of the culture and to produce cultures of I. galbana that could reach an exponential growth phase within 1 wk.

Study design

Test type:

static

Water media type:

saltwater

Total exposure duration:

72 h

Test conditions

Hardness:

6518 mg/l

Test temperature:

28°C

pH:

8.18

Dissolved oxygen:

99%

Salinity:

34,5 PSU

Conductivity:

52 mS/cm

Details on test conditions:

Triplicate cultures (50 mL in 100-mL Erlenmeyer flasks) of I. galbana (3 103 cells/mL) were exposed to a range of concentrations of Al, Ga, or Mo at 28±1 °C for 72 h. The background concentrations of target metals in the seawater controls were approximately 9µg/L Al, 0.04µg/L Ga, and 11 µg/L Mo.
Cell density of I. galbana was measured at 0 h, 48 h, and 72 h using a flow cytometer with a standard filter set and a detector wavelength range of 530 ± 15 nm.
Growth rate (as doublings per day) was calculated as the slope of the linear regression of log10 algal cell concentration versus time. This growth rate (expressed as a percentage of the growth of the control) was used to derive the chronic effect value for growth inhibition. A test was considered valid if the growth rate of control replicates was 2.0 ± 0.4 doublings/d.

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 15.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 6 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ga

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 6 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ga

Basis for effect:

growth rate

Effect concentrations 4

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

> 6 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Ga

Basis for effect:

growth rate

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

The 72-h NOEC for effect of GaCl3 on growth rate of the tropical marine microalga Isochrysis galbana is ≥6 mg Ga/L.