PRELIMINARY TOXICITY TESTS USING THE GREEN-ALGA, ANKISTRODESMUS-FALCATUS

The freshwater green alga Ankistrodesmus falcatus was cultured in incr easing concentrations of Cr, Hg, Cd, Zn, and Al to evaluate the effect of these cations on its growth. Algal growth was estimated by absorba nce at 750 nm. Potassium dichromate was used as reference for test rep roducibility. The EC(50) for 3 tests was 1.890 mg L(-1) with a coeffic ient of variation of 40.25%. The 96 h static EC(50)'s for heavy metals (in mg L(-1) of nominal concentrations) were as follows: Cr6+/K2Cr2O7 1.050; Hg2+/Hg(SCN)(2), 0.162; Hg2+/HgCl2, 0.074; Cd2+/CdCl2 . H2O, 0 .292; Zn2+/ZnSO4 . 7H(2)O, 2.432; and Al3+/Al-2(S0(4))(3) . 18H(2)O, 0 .904. Thus yielding a toxicity series such that Hg > Cd > Al > Cr > Zn . These preliminary results suggest that bioassays using A. falcatus c ould be suitable for evaluating the toxicity of heavy metals in freshw aters. (C) 1997 by John Wiley & Sons, Inc.