Sulphur dioxide

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: No guideline followed. Data reported in figures, not in tables. Study not well documented. No statistics are reported. No data on replicates.

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Toxicity of bisulfite to photosynthesis and respiration

Author:

Sheridan R.P.

Year:

1978

Bibliographic source:

J. Phycol. 14(3): 279-281

Materials and methods

Test guideline

Qualifier:

no guideline followed

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Sulphur dioxide

EC Number:

231-195-2

EC Name:

Sulphur dioxide

Cas Number:

7446-09-5

Molecular formula:

SO2

IUPAC Name:

Sulphur dioxide generated from sulphur by combustion

Test organisms

Test organisms (species):

Chlorococcum sp.

Details on test organisms:

TEST ORGANISM

- Source (laboratory, culture collection): isolated from the Clark Fork River (Montana),
- Age of inoculum (at test initiation):
- Method of cultivation: cloned and cultured in 800ml of medium A (reference 1) in Roux flasks suspended in water-filled, temperature regulated (25°C) and gassed with air.
The light-intenity was 15000lx (VHO cool-white fluorescent lamps).

Study design

Test type:

static

Limit test:

no

Test conditions

Test temperature:

25.0°C

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open / closed
- Material, size, headspace, fill volume:
- Aeration:
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density: Experimental cells, growing logarithmically, were harvested by centrifugation (4000g), diluted to optical density (O.D.) 1 at 680 nm with medium A and prepared for theO2 electrode as described.
- Control end cells density:
- No. of organisms per vessel:
- No. of vessels per concentration (replicates):
- No. of vessels per control (replicates):
- No. of vessels per vehicle control (replicates):


GROWTH MEDIUM
- Standard medium used: no
- Detailed composition if non-standard medium was used: medium A (see Reference 1)


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
- Total organic carbon:
- Particulate matter:
- Metals:
- Pesticides:
- Chlorine:
- Alkalinity:
- Ca/mg ratio:
- Conductivity:
- Culture medium different from test medium:
- Intervals of water quality measurement:


OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH:
- Photoperiod:
- Light intensity and quality:
- Salinity (for marine algae):


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement:
- Other: Photosynthesis, respiration and oxygen exchange rates


TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations:
- Results used to determine the conditions for the definitive study:

Results and discussion

Any other information on results incl. tables

Optimum growth and maximum toxicity both occurred at 25°C, with both growth rate and inhibition of photosynthesis decreasing with a decrease in temperature from this point.

Inhibition of photosynthesis by the addition of NaHSO3 was evident at pH values between 3.0 -5.0 whereas at pH 7 little inhibition was evident and at pH 8.0 NaHSO3 had a stimulatory effect.

The I_k point for light saturation of photosynthesis was ca. 15000 lx.

Using a similar construction as for the determination of the Ik point, the curve showing the inhibitory effect of HSO3^- gives an intersect point at ca. the same light intensity. The HSO3^- curve is approximately the reciprocal of the light intensity curve and resembles the light effinciency curve for photosynthesis.

Inhibition by respiration by HSO3^- treatment, decreased with increasing 'dark time': cells were treated for 60 min in darkness after 0, 60 and 240 of respiration prior to the addition of HSO3^-.

Cells were exposed for 60 minutes to NaHSO3, resuspended in NaHSO3 -free medium and allowed ot recover in light and darkness: The degree of inhibition to photosynthesis by HSO3^- decreased with time, and the rate of recovery in the light exceeded that in darkness.

Applicant's summary and conclusion

Executive summary:

Sheridan (1978) examined the inhibition of photosynthesis in the alga Chlorococcum sp.. Sodium hydrogen sulfite was applied in concentrations between 2 and 10 mMol/l, each of the concentration levels was tested at pH values between 3.0 and 8.0. Photosynthesis was inhibited at pH 3.0 - 6.5 at all concentrations, whereas at pH 7.0 minor inhibition and at pH 8.0 a stimulatory effect at all hydrogen sulfite levels was observed. The study suggests that adverse effects on photosynthesis are mainly caused by pH, rather than by the sulfite concentration.