Formaldehyde toxicity is altered by calcium and organic matter

Formaldehyde is one of the shortlist substances permitted for use in aquaculture. Toxicity of formaldehyde and therapeutical success is influenced by water parameters. However, there is a lack of information on the interaction of organic carbon and calcium (Ca2+) on the toxicity of formaldehyde. Laboratory experiments were conducted to test the combined effects of Ca2+ and natural organic matter (NOM) on formaldehyde toxicity. Zebrafish embryos were exposed to five concentrations of formaldehyde for 144 h. Juveniles exposed to high concentrations died; the embryos exposed to low concentrations were unable to hatch, particularly visible in the groups without NOM. The toxicity-reducing effects of NOM are not attributable to the presence of Ca2+.