Ammonia, anhydrous

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

see read across justification

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 4.77 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

NH3

Basis for effect:

growth rate

Executive summary:

According to the test guideline, the OECD medium used for algae testing contains 15 mg NH4/l. This concentration is the concentrationin the test medium used for algae tests. Therefore, it must be assumed that this concentration is appropriate for good growth of the cultures and can be used as minimum concentration for the NOEC.

Applying the conversion factor from NH4Cl to NH3 the NOEC of > 15 mg NH4Cl/L corresponds to a NOEC of 4.77 mg NH3/L.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

see read across justification

Reason / purpose for cross-reference:

read-across source

Reference substance (positive control):

no

Duration:

18 d

Dose descriptor:

EC50

Effect conc.:

2 700 mg/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

cell number

In the control a lag-phase could be observed until day 11(decline of cell number to approx. 10x10e6 cells/mL). Logarithmic growth could be seen from day 11 - 18 (declineof cell number up to appr. 70x10e6 cells/mL). From day 18 -21 the cell number dropped back to 10x10e6 cells/mL. For this reason the calculation of EC50 is referred to the cellnumber at day 18. Growth occurred in all ammonia concentrations (10-1000 mgN/L), although less growth was found in cultures containingeither very low (10 mg N/L) or very high (750 and 1000 mgN/L) ammonia concentrations. Algal growth was accompanied by a decrease in nitrogen content in the medium, indicating that nitrogen removal wasdue to algal uptake and assimilation. Results demonstratethat C. vulgaris can tolerate high concentrations ofammonia.

In the first about 10 days after start, in all test concentration and in the control a lag phase was observed. Thereafter in the control and some test concentrations an exponential increase in cell number was observed up to day 17 or 18. There are no data available to calculate the 72-hEC50.

The 18 day EC50 was calculated to be 2700 mg N/L.

Conclusions:

The effect of ammonia concentration on growth and physiology of a unicellular green alga, Chlorella vulgaris, was studied. Algal growth was accompanied by a decrease in nitrogen content in the medium, indicating that nitrogen removal was due to algal uptake and assimilation. Results demonstratethat C. vulgaris can tolerate high concentrations of ammonia. The 18 day EC50 was calculated to be 2700 mg/L.

Less growth was found in cultures containing either very low (10 mg/l) or very high (750 and 1000 mg/l) ammonia concentration.

Executive summary:

The effect of ammonia concentration on growth and physiology of a unicellular green alga, Chlorella vulgaris, was studied. Algal growth was accompanied by a decrease in nitrogen content in the medium, indicating that nitrogen removal was due to algal uptake and assimilation. Results demonstratethat C. vulgaris can tolerate high concentrations of ammonia.  The 18 day EC50 was calculated to be 2700 mg/L.

Less growth was found in cultures containing either very low (10 mg/l) or very high (750 and 1000 mg/l) ammonia concentration.

Applying the conversion factor from NH3 -N to NH3, the EC50 of 2700 mg NH3-N/L corresponds to 3283.2 mg NH3/L

Description of key information

An EC50 of 3283.2 mg NH3/L is calculated for Chlorella vulgaris. The NOEC is >= 4.77 mg NH3/L (deduced from the NH4-concentration as requested in the OECD test medium).

Key value for chemical safety assessment

EC50 for freshwater algae:

3 283.2 mg/L

Additional information

The effect of ammonia concentration on growth and physiology of a unicellular green alga, Chlorella vulgaris, was studied by Tam & Wong (1996). Algal growth was accompanied by a decrease in nitrogen content in the medium, indicating that nitrogen removal was due to algal uptake and assimilation. Results demonstrate that C. vulgaris can tolerate high concentrations of ammonia. The 18 day EC50 was calculated to be 2700 mg/L. Algae appear to be of lower sensitivity to the toxicity of ammonia compared to other aquatic organisms including fish, consistent with the fact that ammonia represents a nitrogen source for algae, which is required for growth. According to the test guideline, the OECD medium used for algae testing contains 15 mg NH4/l. This concentration is the concentrationin the test medium used for algae tests. Therefore, it must be assumed that this concentration is appropriate for good growth of the cultures and can be used as minimum concentration for the NOEC. Applying the conversion factor from NH4Cl to NH3 the NOEC of > 15 mg NH4Cl/L corresponds to a NOEC of 4.77 mg NH3/L.