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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP unknown, non-guideline, experimental study, acceptable with restrictions

Data source

Reference Type:
Toxicity of silver to two freshwater algae, Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata, grown under continuous culture conditions: influence of thiosuphate.
Hiriart-Baer V, Fortin C, Lee D-Y, Campbell PGC.
Bibliographic source:
Aquatic Toxicology 78:136-148

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
Batch cultures of C. reinhardtii in exponential growth were transferred to turbidostats. For each turbidostat unit, the growth rate was determined for 1 day in control (Ag-free) medium and this rate was used as the reference growth rate. After this initial period, 110mAg was added to the culture chamber and to the influent medium to obtain a nominal Ag concentration of 10 nM. The algal growth rate was monitored, and once it had stabilized (normally within 18-24 h) the Ag concentration was increased to 20 nM in both the culture medium and the influent medium. Algal growth rates were monitored as before and a stepwise increase in Ag concentration was carried out in the sequence 10, 20, 30, 50 and 80 nM Agtot. For each replicate, an aliquot of 70 ml of the culture medium from the turbiostat culture was collected at the end of each exposure period (i.e., at ~ 18 - 24 h intervals) and this volume was then used for a series of analyses: total Ag; dissolved Ag, intracellular Ag; cell density and size; chlorophyll-a concentrations; cellular carbon, nitrogen and sulphur contents and medium pH.
GLP compliance:
not specified

Test material

impurity 1
Chemical structure
Reference substance name:
Silver methanesulphonate
EC Number:
EC Name:
Silver methanesulphonate
Cas Number:
Molecular formula:
silver methanesulphonate
Test material form:
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Sampling and analysis

Analytical monitoring:
Details on sampling:
70 ml samples of culture medium both exposure conentrations and control at end of each exposure period.

Test organisms

Test organisms (species):
Chlamydomonas reinhardtii
Details on test organisms:
Test organisms (species) Chlamydomonas reinhardtii (UTCC 11)
Details on test organisms - source University of Toronto Culture Collection
Details on test organisms - holding conditions prior to test Batch cell cultures maintained axenically in 100 ml of modified high salt medium at an ionic strength of 6 meq l-1. Maintenance batch cultures were grown in 250 ml polycarbonate Erlenmeyer flasks under constant illumination of 100 ± 10 μEm-1 s-1 with rotary agitation at 50 rpm at 20ºC. Cultures maintained weekly by transferring ~ 2 ml of culture to fresh, sterile medium (pH7; no pH buffers). Culture media autoclaved prior to addition of a filter-sterilized trace metal mix to avoid potential metal precipitation at high temperature.
Details on test organisms - life stage of test species used Exponential growth phase

Study design

Test type:
Water media type:
Limit test:
Total exposure duration:
24 h
Remarks on exposure duration:
18-24 hrs at each concentration
Post exposure observation period:
Not applicable

Test conditions

no data
Test temperature:
pooled effluent pH across all treatments 7 ± 0.3 (6.7 - 7.5; min-max)
Dissolved oxygen:
no data
not applicable
Nominal and measured concentrations:
Dissolved Ag concentrations measured in the turbidostat effluent were less than the total concentrations in the effluent, reflecting uptake of silver by the growing algal biomass; the % dissolved Ag varied between 50 and 85%, according to the influent concentration, the algal growth rate and the algal species. To evaluate Ag concentration algae exposed to in the turbidostats, free Ag+ in the effluent stream was calculated. The exposure medium was considered to contain no appreciable Ag binding ligands. The authors suggest that the EC50s values calculated from the free Ag+ concentrations in the effluent probably overestimated silver toxicity (underestimate EC50) since Ag+ in the effluent was measured after filtration and subsequent control experiments indicated that some adsorptive loss of Ag onto the filters could have occurred.
Details on test conditions:
Test vessel: Turbidostats - custom-made units consisting of a 1 l polycarbonate jar with an inserted pair of quartz cylinders containing an emitting and a detecting probe (λ = 910 nm, pulsed at 1 kHz and integrated over 2.3s). When measured turbidity exceeded set threshold value, a perstaltic pump was triggered to dilute the culture medium (10 ml min-1) and remove an equivalent volume (inlet and outlet tubes were placed at the bottom and surface of the culture vessel, respectively).
3 replicates per concentration

- Sterile test conditions: yes

DETERMINATION OF GROWTH RATE: From medium replacement volume for a given time period.

Stepwise increment, 10, 20, 30, 50 and 80 nM Ag.
Reference substance (positive control):

Results and discussion

Effect concentrations
Key result
24 h
Dose descriptor:
Effect conc.:
0.54 µg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
element (dissolved fraction)
Basis for effect:
growth rate
Remarks on result:
other: recalculated from author's data
Details on results:
no data
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
Student t-test with Bonferroni correction was used to make pairwise comparisons of the batch culture growth data. ANOVA used for effects of Ag treatments on growth rates and chemical composition. All statistical analyses carried out using Systat V.10. Significance set at p = 0.05.

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
The EC10 of silver to Chlamydomonas reinhardtil, recalulated from the author's data, is 0.54 µg/L.
Executive summary:

The toxicity of silver toChlamydomonas reinhardtilwas assessed in continuous algal cultures grown in turbidostats, with a stepwise increaments of the silver concentration.

The EC10 of the test substance toChlamydomonas reinhardtil, recalulated from the author's data, is 0.54 µg/L.