Utility of delayed fluorescence as endpoint for rapid estimation of effect concentration on the green alga Pseudokirchneriella subcapitata.

Algal growth inhibition tests for environmental risk assessment require improved efficiency to evaluate large numbers of chemicals. As an endpoint for rapid estimation of the effect concentration of test chemicals, we propose the delayed fluorescence (DF) measurement from an alga 24 h after exposure. Eight chemicals (bifenox, bromoxynil, bensulfuronmethyl, diuron, diflufenican, thiobencarb, m-chlorophenylhydrazone and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) were tested. The EC50 values from the 24 h DF measurement were similar to those from the conventional 72 h growth test for seven tested chemicals excepting thiobencarb. We conclude that 24 h DF measurement is a possible endpoint for rapid estimation of the EC50 values obtained in the 72 h growth test for those seven chemicals.