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Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No data on purity and study has not been conducted to GLP. Not conducted to OECD guidelines, however study looks to have been reasonably conducted.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Examination of the acute toxicity of the test material to Lemna minor L. and Azolla filiculoides Lamk. The exposure time was 7 days in freshwater.
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
other: Lemna minor & Azolla filiculoides.
Details on test organisms:
Lemna minor was collected from the Shuishang Lake in Tianjin City. The stock was cultured in the laboratory using Hunter solution (Hunter 1953).
Azolla filiculoides was collected from the Weijin River in Tianjin City. The stock was cultured using Hogland solution (Mordechai, 1989).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Test temperature:
25 ± 1 °C
Nominal and measured concentrations:
Lemna minor: 5.0, 10.0, 25.0, 50.0 μg/L
Azolla filiculoides: 1.0, 2.5, 5.0, 10.0, 25.0, 50.0 μg/L
Details on test conditions:
Lemna minor: Toxicity tests were conducted in a series of 100 mL beakers. Each beaker contained 80 mL of test water and 12 fronds (or 6 plants). Five concentrations of the test material (0, 5.0, 10.0, 25.0, 50.0 μg/L) were used as experimental treatments, each replicated 3 times. The number of fronds in each beaker was counted every day. After 4 days the chlorophyll content of each beaker was determined. A photoperiod of 16hr light 8hr dark was used at 25 ± 1 °C.

Azolla filiculoides: Tests were conducted in 250 mL beakers. 200 mL of test water containing seven concentrations of the test material (0, 1.0, 2.5, 5.0, 10.0, 25.0, 50.0 μg/L) and 0.2 g (fresh wt) plant were placed in beakers, each replicated 3 times. After 7 days, the plant wet weight and the chlorophyll content of each beaker were determined. A photoperiod of 16hr light/ 8hr dark was used at 25 ± 1 °C.

After each test the whole plant was homogenised with 10 mL acetone to extract chlorophyll. The extraction solution was put into refrigerator for 96 hours at 4 %. Then the solution was centrifuged at 3000 x g for 15 minutes. The absorbance of clear solution was determined at 663 and 64.5 nm. The chlorophyll content and growth inhibition calculations can be seen in the Illustration section.
Duration:
96 h
Dose descriptor:
IC50
Effect conc.:
30.83 µg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: The correlation coefficient was 0.877.
Duration:
96 h
Dose descriptor:
IC50
Effect conc.:
12.4 µg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: chlorophyll content
Remarks on result:
other: The correlation coefficient of the data was 0.916.
Duration:
7 d
Dose descriptor:
IC50
Effect conc.:
8.17 µg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: The correlation coefficient was over 0.9.
Duration:
7 d
Dose descriptor:
IC50
Effect conc.:
1.84 µg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: chlorophyll content
Remarks on result:
other: The correlation coefficient was over 0.9.
Details on results:
The initial chlorophyll content was 0.44 mg/L of each beaker in L. minor tests. The data (table 1) show the toxic effect of the test material on the growth and chlorophyll content in beakers of L. minor. According to the fronds data, the 96 hr IC50 of the test material to L. minor was 30.83 μg/L. The correlation coefficient was 0.877. The 96 hr IC50 of the test material for chlorophyll content in L. minor test was 12.4 μg/L. The correlation coefficient of the data was 0.916.

The initial chlorophyll content was 14.44 mg/L in A. filiculoides tests. The data ( table 2) show the toxic effect of the test material on the growth and chlorophyll content in beakers of A. filiculoides. The IC50 of the test material (7 days) for growth of A. filiculoides was 8.17 μg/L. The IC50 of the test material (7 days) for chlorophyll content of A. filiculoides was 1.84 μg/L. All correlation coefficients were over 0.9.

The results showed that concentration levels of the test material being at μg/L the toxicity of the test material to L. minor and A. filiculoides was very high. The data suggested that chlorophyll content in beakers was more susceptible than growth.
Reported statistics and error estimates:
The test data were analysed for statistical differences by an analysis of variance (ANOVA), studying the effect of each treatment of the test material.
Validity criteria fulfilled:
not specified
Conclusions:
According to the fronds data, the 96 hr IC50 of the test material to L. minor was 30.83 μg/L. The correlation coefficient was 0.877. The 96hr IC50 of the test material for chlorophyll content in L. minor test was 12.4 μg/L. The correlation coefficient of the data was 0.916.
The IC50 of the test material (7 days) for growth of A. filiculoides was 8.17 μg/L. The IC50 of the test material (7 days) for chlorophyll content of A. filiculoides was 1.84 μg/L. All correlation coefficients were over 0.9.
Executive summary:

Examination of the acute toxicity of the test material to Lemna minor L. and Azolla filiculoides Lamk was performed. The exposure time was 7 days in freshwater.

The initial chlorophyll content was 0.44 mg/L of each beaker in L. minor tests. According to the fronds data, the 96hr IC50 of the test material to L. minor was 30.83 μg/L. The correlation coefficient was 0.877. The 96 hr IC50 of the test material for chlorophyll content in L. minor test was 12.4 μg/L. The correlation coefficient of the data was 0.916.

The initial chlorophyll content was 14.44 mg/L in A. filiculoides tests. The IC50 of the test material (7 days) for growth of A. filiculoides was 8.17 μg/L. The IC50 of the test material (7 days) for chlorophyll content of A. filiculoides was 1.84 μg/L. All correlation coefficients were over 0.9.

The results showed that concentration levels of the test material being at μg/L, the toxicity of the test material to L. minor and A. filiculoides was very high. The data suggested that chlorophyll content in beakers was more susceptible than growth.

Description of key information

Key value for chemical safety assessment

Additional information

In a supporting study for this endpoint (Zhihui et al, 1997), the acute toxicity of the test material to Lemna minor L. and Azolla filiculoides Lamk was examined. The exposure time was 7 days in freshwater.

According to the fronds data, the 96 hr IC50 of the test material to L. minor was 30.83 μg/L. The correlation coefficient was 0.877. The 96 hr IC50 of the test material for chlorophyll content in L. minor test was 12.4 μg/L. The correlation coefficient of the data was 0.916. The IC50 of the test material (7 days) for growth of A. filiculoides was 8.17 μg/L. The IC50 of the test material (7 days) for chlorophyll content of A. filiculoides was 1.84 μg/L. All correlation coefficients were over 0.9.

A reliability rating of 2 was assigned to this study, according to the criteria of Klimisch, 1997 as although there was limited information on test material and no information on GLP, the methodolgy is well documented.