Toxicity of metals on the growth of Raphidocelis subcapitata and Chlorella kessleri using microplate bioassays

SUMMARY The toxicities of CuCl 2 ·2 H 2 O, CoCl 2 ·6 H 2 O, HgCl 2 and FeCl 3 ·6 H 2 O were tested using algal growth inhibition bioassays on two freshwater green algae Raphidocelis subcapitata (= Selenastrum capricornutum ) and Chlor-ella kessleri . The aim was to compare the algal growth in-hibition EC50s obtained from the toxicity testing of four metal compounds on microplates with the standard flask assay, as well as to compare the sensitivity of tested algae to selected metal compounds. The results showed that mer-cury was the most toxic element for both algae. The toxic-ity hierarchy for both algae, according to the mean values from both methods was Hg>Cu>Co>Fe. C. kessleri was more sensitive (0.11–8 mg L -1 , with average 1.78 mg L) than R. subcapitata (0.33–9.4 mg L -1 ; average 2.06 mg L -1 ) to the tested metal compounds. Algal bioassay in micro-plates gave comparable results to standard flask bioassay for the tested algae and can be recommended for routine toxicity testing.