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Competition among zinc, manganese, and cadmium uptake in the freshwater alga Scenedesmus vacuolatus
Author(s) -
Töpperwien Stefanie,
Behra Renata,
Sigg Laura
Publication year - 2007
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/06-181r.1
Subject(s) - cadmium , zinc , scenedesmus , scenedesmus obliquus , manganese , chemistry , environmental chemistry , competition (biology) , algae , ecotoxicology , bioaccumulation , toxicity , nuclear chemistry , biotic ligand model , biology , botany , ecology , organic chemistry
In the present study, Zn and Mn competition with Cd uptake was investigated in the freshwater alga Scenedesmus vacuolatus. Scenedesmus vacuolatus was exposed to experimental media with Cd and either Zn or Mn in short‐term experiments; long‐term experiments were undertaken to investigate the effect of growth on Cd accumulation. Cadmium accumulation in S. vacuolatus could be detected at very low exposure concentrations (free Cd 2+ , 2 × 10 −14 to 1 × 10 −11 M), and uptake was proportional to the free‐Cd 2+ concentration. Zinc was an effective competitive inhibitor of Cd uptake when the Zn 2+ to Cd 2+ ratio was greater than 14 in the exposure medium, whereas Mn competed with Cd for uptake above a Mn 2+ to Cd 2+ ratio of greater than 10,000. Binding constants for Cd and Zn affinity to the transport sites were determined ( K Zn and K Cd ). Values for K Zn were slightly higher (log K = 9.4–9.8) than values for K Cd (log K = 8.9–9.8). In contrast, Cd seemed not to compete with the Mn‐binding sites for uptake over the Mn concentration range from 1 × 10 −10 to 1 × 10 −8 M. Determined values for the binding constants of Zn and Cd show that a simple model can be applied to predict Cd uptake at known Zn and Cd concentrations. The environmental implications of these results are discussed with respect to potential Cd toxicity for aquatic organisms.