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Toxicity to aquatic algae and cyanobacteria

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Zinc chloride studies

Study 1:

A study was conducted to determine the toxicity of the test substance against P. subcapitata after acclimation to natural soft water according to OECD Guideline 201. Comparison was done with sensitivity of the alga in moderately hard water. Total and dissolved zinc concentrations were measured by flame AAS. Dissolved zinc concentrations (at the beginning of the test) were used to determine 72 h NOECs. Under the study conditions, the 72 h NOEC was within range of 50 to 93 µg/L (arithm. mean) (Muyssen, 2003).

Study 2:

A 72 h algae growth inhibition test was used to examine the toxicity of zinc to the marine diatom N. closterium. The mean EC10 for inhibition of cell division from 4 tests was 84 µg/L (Johnson, 2007).

Study 3:

The toxicity of zinc to the growth rate of the marine brown macroalgae F. vesiculosus was examined. Significant reductions in growth rate were observed at 1400 µg/L but not at 100 µg/L, the highest tested concentration lower than the LOEC (Stromgren, 1979).

Study 4:

The toxicity of zinc to the growth rate of the marine brown macroalga F. spiralis was examined. Significant reductions in growth rate were observed at 1400 µg/L. An EC10 (613.2 µg/L) could be recalculated based on average growth rates for this assessment (Stromgren, 1979).

Study 5:

A study was conducted to develop a biotic ligand model for zinc in freshwater. Several organisms were exposed to zinc in media with varying conditions of pH, hardness and DOC. Validation of the derived models was done in natural waters. Tests were done according to a standard protocol. Dissolved zinc concentrations were measured at the start and at the end of the test by flame AAS or ICP. Reported effect concentrations were based on tests using ‘standard’ OECD 201 medium and on concentrations measured at the start of the test. Under the study conditions, the 72 h NOEC for Pseudokirchneriella subcapitata lay within the range of 4.9 to 124 µg/L (De Schamphelaere, 2003).

 

Zinc sulfate studies

Study 1:

The toxicity of zinc to sporophyte production by gametophytes of the marine macroalga M. pyrifera was tested in 16 d tests and the effect of zinc on zoospore germination and growth of germination tubes was tested 3 times in 48 h bioassays. Significant effects on sporophyte production were observed at 1071 µg/L Zn and on tube growth at 553, 589 and 1090 µg/L. The 48 h exposure bioassay was more sensitive than the 16 d exposure test conducted within the same study. This study was published twice (Anderson 1988).

Study 2:

A study was conducted to determine the effect of different pH on the toxicity of zinc to Chlorella. Tests were not conducted according to a standard protocol, but were of good quality and considered useful for setting the PNEC freshwater. Under the study conditions, the 48 h EC10 value was within range of 16 to 350 µg/L (Wide, 2006).

Study 3:

Clones of the marine diatom N. closterium, collected in clean seawater, were exposed to zinc for three days in the laboratory. Zinc concentrations of 60 µg/L inhibited algal growth by 18% and an EC10 value of 52 µg/L was recalculated (Fisher, 1980).

Study 4:

Clones of the marine diatom A. japonica, collected in clean seawater, were exposed to zinc for four days in the laboratory. Zinc concentrations of 20 and 40 µg/L Zn inhibited algal growth by 0.6 and 23.3%, respectively. An EC10 value of 20.6 µg/L was recalculated for this assessment (Fisher, 1981).

 

Acrylic acid studies

Study 1:

An acute toxicity study was conducted with Selenastrum capricornutum according to EPA OTS Guideline 797.1050 and OECD Guideline 201 using a static design. Nominal exposure concentrations were 0.13, 0.25, 0.5, 1.0, 2.0 mg/L. At time 0, the analyzed concentrations were 0.15, 0.26, 0.49, 0.96, 1.9 mg/L. After 96 h, analyses of the test media were all below the limit of detection. The loss of acrylic acid was considered to be related to volatility and/or adsorption to the vessels and the algae. Since such a loss of test substance did not occur in any of the other freshwater algae tests, this study has to be regarded as valid with restrictions. Under the study conditions, growth inhibition of algae was observed at all concentrations from 24 through 96 h. Based on cell counts, the 72 and 96 h EC50 values were 0.14 and 0.17 mg/L (nominal), respectively. The 96 h NOEC was <0.13 mg/L (BAMM, 1990).

Study 2:

An algal growth inhibition study with Scenedesmus subspicatus was conducted according to EU Method C.3 to provide information on potential ecotoxicological hazards from exposure to acrylic acid. Nominal test concentrations were 1, 2.5, 5, 10, 20, 40 mg/L. Since the analytical recovery rates were > 80%, all effect values were based on nominal concentrations. Under the study conditions, the relevant 72 h effect concentrations were determined to be EC50 (growth rate): 0.205 mg/L and EC10 (growth rate): 0.031 mg/L (nominal) (Huels AG 1995).

Study 3:

An algal growth inhibition study was conducted with Scenedesmus subspicatus according to EU Method C.3 using a static design. Nominal exposure concentrations were 0.0078, 0.016, 0.031, 0.063, 0.13, 0.25, 0.5, 1, 10, 100 (not neutralised) and 100 (neutralised) mg/L. Analytical recovery rates were between 94 – 101% of nominal concentrations. Therefore, all effect values were based on nominal test substance concentrations. For determination of acute ecotoxicity of acrylic acid, the EC50 value for growth rate was determined. For the assessment of chronic ecotoxicity of acrylic acid, the corresponding EC10 value was calculated (according to Guidance on Information Requirements and Chemical safety - R.10). Under the study conditions, the relevant 72 h effect concentrations were determined to be EC50 (growth rate): 0.13 mg/L and EC10 (growth rate): 0.03 mg/L (BASF AG 1994).