Factors affecting thallium and chromium toxicity to marine algae

Abstract

The acute toxicity of thallium and chromium to marine phytoplankton was determined in enrichment culture bioassays (1). The results indicated minimal effective concentrations of 0.7 10 − 1.1 10 −6 M thallium on Phaeodactylum tricornutum growth respectively for the monovalent and the trivalent forms. Separate studies on Dunaliella tertiolecta confirmed the higher toxicity of the monovalent form with respect to the trivalent one (0.4 10 −6 M and 0.9 10 −6 M, respectively). In experiments with Cr, the minimal effective concentration of Cr (VI) was 1 10 −4 M for both algal species in marine waters. Cr (VI) toxicity was found to be strongly dependent on mean salinity due to the competitive role of sulphate. Figure 1 Cr (III) concentrations lower than 4 10 −4 M did not significantly reduce the growth rate but produced a longer phase lag, while at concentrations of 4 10 −4 M Cr (III) no growth was observed. The toxicity of both Tl (III) and Cr (III) is shown to be reduced by complexation with EDTA.