Calcium sulphite

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study according to standard guideline. However, chemical analytics not given, replicate numbers not stated (except sub samples for fluorescentce measurement), important water quality parameters not given, control data missing (validity criteria unassessible).

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: U.S. EPA method 1003.0, 1994. Short-term methods for estimating the chronic toxicity of effluents and receiving waters to freshwater organisms

Version / remarks:

3rd ed. EPA/600/4-91/002. Environmental
Monitoring Systems Laboratory, Cincinnati, OH

Principles of method if other than guideline:

Duckweed Lemna minor was exposed to different concentrations of calcium (CaCl2) diluted in 20 % diluted duckweed medium according to U.S. EPA method 1003.0, 1994. The dilution of the medium was done to lower the background concentration of salts present in the medium. Lemna minor was exposed for up to 7 days in a static system and thereafter, the acute 48 h - EC10 and EC50 values on mortality as well as the chronic 7 d - EC10 and EC50 values for the number of fronds were determined.

GLP compliance:

not specified

Remarks:

publication

Specific details on test material used for the study:

CaCl2; no further details

Analytical monitoring:

no

Details on sampling:

Live and dead fronds were counted after 2 d (acute test) and 7 d (chronic test). A frond was considered dead when no green pigment was visible.

Vehicle:

no

Details on test solutions:

Duckweed medium was preopared according to U.S. EPA method 1003.0, 1994 and thereafter was diluted to one-fifth (20% medium) of the normal concentration so that the background salt concentrations would be lower. Specific conductance of each solution was measured with a conductivity meter (Model 30, YSI) initially and at the end of the incubation.

Test organisms (species):

Lemna minor

Details on test organisms:

TEST ORGANISM
- Common name: duckweed
- Scientific name: Lemna minor
- Strain: not stated
- Source: Carolina Biological Supply
- Inoculum (start): 20 fronds per peaker
- Method of cultivation: in 20% duckweed medium with weekly renewal of the medium

ACCLIMATION
- Acclimation period: 4 weeks
- Media/conditions: the same for culturing and testing

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Hardness:

not stated

Test temperature:

not stated

Dissolved oxygen:

not stated

Salinity:

not stated

Conductivity:

At 48 h - EC10 and EC50 (survival): 12 ± 0.65 mS/cm and > 27 mS/cm
At 7 d - EC10 and EC50 (Frond number): 1.5 ± 0.042 mS/cm and 6.3 ± 0.18 mS/cm

Nominal and measured concentrations:

nominal (target concentration):
0 (control), 0.001, 0.0025, 0.005, 0.02, 0.035, 0.05 and 0.1 M CaCl2/L + background concentration of medium (= 1 mM Ca2+; Cl- = trace)
0 (control), 111, 277, 555, 2220, 3884, 5549, 11100 mg CaCl2l/L

Details on test conditions:

TEST SYSTEM
- Test vessel: beaker (volume not stated)
- Type: closed
- Aeration: not stated
- System: static
- # of colonies per vessel:not stated
- # of fronds per colony: 20
- replicates: 5 (treatment), 5 control

GROWTH MEDIUM
- Standard medium used: yes, duckweed medium but diluted to one-fifth

OTHER TEST CONDITIONS
- Sterile test conditions: not stated
- Adjustment of pH: not stated
- Photoperiod: 12/12, light/dark
- Light intensity and quality:fluorescent lights, 2500 lux

EFFECT PARAMETERS MEASURED:
- frond number: manual counting after 2 and 7 days

Reference substance (positive control):

not specified

Duration:

2 d

Dose descriptor:

EC10

Effect conc.:

> 8 213 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CaCl2

Basis for effect:

other: survival

Duration:

2 d

Dose descriptor:

EC50

Effect conc.:

> 8 213 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CaCl2

Basis for effect:

other: survival

Duration:

7 d

Dose descriptor:

EC10

Effect conc.:

755 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CaCl2

Basis for effect:

frond number

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

3 219 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

CaCl2

Basis for effect:

frond number

Duration:

2 d

Dose descriptor:

EC10

Effect conc.:

> 3 006 mg/L

Nominal / measured:

estimated

Conc. based on:

element

Remarks:

Ca2+

Basis for effect:

other: survival

Remarks on result:

other:

Remarks:

this includes background [Ca2+]

Duration:

2 d

Dose descriptor:

EC50

Effect conc.:

> 3 006 mg/L

Nominal / measured:

estimated

Conc. based on:

element

Remarks:

Ca2+

Basis for effect:

other: survival

Remarks on result:

other:

Remarks:

this includes background [Ca2+]

Duration:

7 d

Dose descriptor:

EC10

Effect conc.:

313 mg/L

Nominal / measured:

estimated

Conc. based on:

element

Remarks:

Ca2+

Basis for effect:

frond number

Remarks on result:

other:

Remarks:

this includes background [Ca2+]

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

1 202 mg/L

Nominal / measured:

estimated

Conc. based on:

element

Remarks:

Ca2+

Basis for effect:

frond number

Remarks on result:

other:

Remarks:

this includes background [Ca2+]

Details on results:

Survival as well as frond number of control not given. It was not stated whether endpoints were calculated on target- or initial concentrations (for details see "Nominal and measured concentrations").

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

The effective concentration for 10 and 50% (EC10 and EC50) values were estimated according to U.S. EPA method 1003.0, 1994. Briefly, linear regression was used to interpolate between the two experimental treatments that bracketed the EC10 or EC50. To determine the relative toxicity of individual cations and anions, a two-way analysis of variance (ANOVA) with replication using cation type and anion type as factors was applied to all of the results in which the anion concentrations were 0.1 M. Because the total anion concentration was identical for each salt, observed differences in end points could be attributed to the presence or absence of individual ion species. The two-way ANOVA also tested for interactions between cations and anions.

Validity criteria fulfilled:

not applicable

Remarks:

since important water parameters during the test as well as control growth/biomass have not been stated

Conclusions:

Duckweed Lemna minor was exposed to different concentrations of calcium in the form of calcium chloride (CaCl2) for 2 and 7 days in a static system according to EPA method 1003.0, 1994. For the endpoint "survival", the 48 h - EC10 and EC50 values both amounted to >8213 mg CaCl2/L (nominal), which is equivalent to an elemental calcium concentration of >3006 mg Ca2+/L (including background). For the endpoint "frond number", the 7 d - EC10 and EC50 values amounted to 755 and 3218 mg CaCl2/L (nominal), respectively, which is equivalent to elemental calcium concentrations of 313 and 1202 mg Ca2+/L (including background), respectively. Since important water parameters during the test as well as frond numbers of control have not been stated, it was not possible to assess the test's validity.

Description of key information

Simmons (2012) investigated the effects of potassium in form of CaCl2 on duckweed Lemna minor after a 7-days static exposure; the overall lowest 7-day EC10 and EC50 values (frond number) amount to 313 and 1202 mg Ca2+/L, respectively, and are above the OECD test limit (Simmons, 2012).

In European stream water, calcium has a median background concentration of 42.7 mg Ca2+/L (FOREGS). Calcium is an essential macronutrient of aquatic macrophytes. Major functions of calcium in plants encompass the formation and stability of cell walls and the maintenance of membrane structure and permeability. Calcium activates a variety of enzymes and regulates many responses of cells to stimuli. It is therefore present in media used for macrophyte tests (e.g. OECD Test Guideline 221 - Lemna sp. Growth Inhibition Test).

In sum, calcium as and essential element has a very low potential for toxicity to aquatic plants.