title: Metal stoichiometry in predicting Cd and Cu toxicity to a freshwater green alga Chlamydomonas reinhardtii.
abstract: In this study, we quantified the accumulation and toxicity of cadmium and copper in a freshwater green alga, Chlamydomonas reinhardtii, under different phosphate conditions. The accumulated Cd and Cu concentrations increased significantly with increasing ambient P concentrations and free metal ion concentrations. The metal:P ratio remained independent of the ambient P concentration. For the three pulse-amplitude-modulated parameters, the median inhibition concentrations were 1.5-1.6x and 2.0x higher, but the medium inhibition cellular quota was 2.2x and 1.2x lower for cells maintained at 0.1 microM P than for cells maintained at 10 microM P for Cd and Cu, respectively. Furthermore, the difference in metal toxicity decreased (for Cd) or disappeared (for Cu) when the toxicity was expressed by the metal:P ratio in the cells, indicating that the stoichiometry of metals and P can be better used to predict the toxicity of metals. It is necessary to consider the stoichiometry of metals in predicting metal toxicity in phytoplankton.
authors.affiliation: Department of Biology, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong. wwang@ust.hk
authors.forename: Wen-Xiong
authors.initials: WX
authors.lastname: Wang
authors.forename: Robert C H
authors.initials: RC
authors.lastname: Dei
mesh_terms: D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D002104:Cadmium / Q000737:chemistry / Q000633:toxicity*; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000378:metabolism; D003300:Copper / Q000737:chemistry / Q000633:toxicity*; D005470:Fluorometry; D007477:Ions; D008956:Models, Chemical; D010710:Phosphates / Q000032:analysis / Q000378:metabolism; D010788:Photosynthesis; D018675:Toxicity Tests; D014131:Trace Elements / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*
chemical_list: D007477:Ions; D010710:Phosphates; D014131:Trace Elements; D014874:Water Pollutants, Chemical; D002104:Cadmium; D003300:Copper