Bioaccumulation And Toxicity Studies Of Heavy Metals In Ankistrodesmus Convolutus Corda






bioaccumulation, heavy metals, toxicity studies, Ankistrodesmus convolutus corda, microalgae


Nine freshwater microalgal species of Malaysia, Chlorella vulgaris (isolate 001), Scenedesmus sp. (isolate 039), Mougeolia sp. (isolate 069), Ulothhx sp. (isolate 071), Chlorella sp. (isolate 078), Ankistrodesmus convolutus (isolate 101), Chlorococuum sp. (isolate 110), Synechococcus sp. (isolate 075), Euglena sp. (isolate 058), and including two species Oocystis polymorpha UTEX 1645 (isolate 169) and Ankistrodesmus arcuatus UTEX LB 1379 (isolate 170) from the UTEX Collection, Texas, were used in 96 h single heavy metal (Cd, Co, Cr, Cu, Fe, Mn and Zn) exposure static studies for preliminary toxicity test. This was done by incubating the microalgae in a range of metal concentrations in Bold Basal Medium (BBM) in multiwell plates. Of these species Ankistrodesmus convolutus Corda. (isolate No. 101) was selected for further toxicity and bioaccumulation tests. Toxicity tests were conducted to investigate the toxic effect of Cd, Co, Cr, Cu, Fe, Mn and Zn on the growth of A. convolutus. Results from the toxicity tests showed that A. convolutus is tolerant to most of the heavy metals. The order of toxicity in A. convolutus based on 96 h IC50 and 1C 25 are Zn = Mn > Cu > Cd > Cr > Co > Fe. A. convolutus was most sensitive to Fe (IC50 = 0.52 mgL-11) and most tolerant to Mn (IC50 = 16.14 mgL-11). Ankistrodesmus convolutus was exposed to different concentrations of seven metals (Cd, Co, Cr, Cu, Fe, Mn and Zn) to observed patterns of heavy metal uptake (bioaccumulation) in short-term test. Four main metal accumulation patterns were observed in this study: Pattern 1 : rapid metal uptake during the first hour of exposure and followed by a gradual release; Pattern 2 : continuous uptake appears during the entire hour of exposure till an equilibrium level; Pattern 3 : rapid uptake during the first hour exposure and followed by a gradual release till equilibrium level is reached; Pattern 4 : alternating uptake and release of metal. In general, maximum uptake occurred in the first hour of exposure, followed by further gradual uptake, or gradual release, or an alternating uptake - release pattern. Metal bioaccumulation increased with increasing concentration of metal in the medium. Cells in logarithmic growth were more active in metal bioaccumulation than cells at stationary growth.