Zinc selenite

Toxicity to aquatic algae and cyanobacteria

Description of key information

Acute toxicity to algae: 

Good quality and relevant acute toxicity data are available for 5 species. After checking and updating the data base, the data are normalized towards pH 6 and 8 and towards realistic worst-case conditions for DOC (2 mg/L) and a water hardness of 40 mg Ca/L. If several data points were available on a same species, the geomean of the normalized values was calculated and used for the analysis.

Key data (lowest geomean EC50 values) are: 
- pH 6: 0.308 mg Zn/L for Pseudokircherniella subcapitata (= Selenastrum capricornutum)
- pH 8: 0.041 mg Zn/L for Pseudokircherniella subcapitata (= Selenastrum capricornutum)

Chronic toxicity to algae: 
chronic toxictiy to freshwater algae: lowest NOEC 0.024 mg Zn/l (Pseudokircherniella subcapitata 
=Selenastrum capricornutum; geomean of 51 data)

chronic toxicity to marine algae: 6 species available which NOECs range between 0.0855 (Nitzschia 
closterium) and 0.45 (Phaeocystis antarctica) mg/l (dissolved concentrations)

Additional information

Acute freshwater toxicity tests of high quality and relevancy performed according to standard protocol. Information is available for 5 species. The lowest geomean IC50 value after normalisation to pH 6 and 8 is taken as reference value for classification for acute effect at low and high pH.

 

Chronic freshwater toxicity tests of high quality and relevancy according to standard protocol or equivalent. Chronic toxicity data were retrieved for 4 different freshwater alga species, 2 different green algae, 2 diatoms In addition,  toxicity data for 1 cyanobacteria has been retrieved.

For the green alga Pseudokirchneriella subcapitata, non-normalised 72 h chronic toxicity values for the endpoint growth rate varied between 4.9 and 131 µg Zn/L. For the tropical Chlorella sp. 48 h EC10 varied between 22.9 and 646 µg Zn/L for the endpoint growth rate. Toxicity data for 2 different freshwater diatoms, i.e., Planothidium lanceolatum and Navicula pelliculosa, revealed 72 h EC10 (endpoint growth rate) values of respectively 234 µg Zn/L and of 280 µg Zn/L. A chronic toxicity value of 1000 µg Zn/L was noted for the cyanobacteria Microcystis aeruginosa.

 

Chronic seawater tests of high quality and relevancy according to standard protocol or equivalent. Chronic toxicity data were retrieved for 6 different marine micro-alga species, i.e., Conticriba weissflogii, Cryothecomonas armigera, Nitzschia Closterium, Phaeocystis Antarctica, Pleurochrysis roscoffensis and Thalassiosira pseudonana. Chronic toxicity data for marine algae (for the endpoint growth) varied between 85.5 µg Zn/L for Nitzschia closterium and 450 µg Zn/L for Phaeocystis antarctica.