Toxicity of arsenic species to three freshwater organisms and biotransformation of inorganic arsenic by freshwater phytoplankton (Chlorella sp. CE-35)

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Journal Article
Ecotoxicology and Environmental Safety, 2014, 106 pp. 126 - 135
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In the environment, arsenic (As) exists in a number of chemical species, and arsenite (AsIII) and arsenate (AsV) dominate in freshwater systems. Toxicity of As species to aquatic organisms is complicated by their interaction with chemicals in water such as phosphate that can influence the bioavailability and uptake of AsV. In the present study, the toxicities of AsIII, AsVand dimethylarsinic acid (DMA) to three freshwater organisms representing three phylogenetic groups: a phytoplankton (Chlorella sp. strain CE-35), a floating macrophyte (Lemna disperma) and a cladoceran grazer (Ceriodaphnia cf. dubia), were determined using acute and growth inhibition bioassays (EC50) at a range of total phosphate (TP) concentrations in OECD medium. The EC50values of AsIII, AsVand DMA were 27±10, 1.15±0.04 and 19±3mg L-1for Chlorella sp. CE-35; 0.57±0.16, 2.3±0.2 and 56±15mgL-1for L. disperma, and 1.58±0.05, 1.72±0.01 and 5.9±0.1mgL-1for C. cf. dubia, respectively. The results showed that AsIIIwas more toxic than AsVto L. disperma; however, AsVwas more toxic than AsIIIto Chlorella sp. CE-35. The toxicities of AsIIIand AsVto C. cf. dubia were statistically similar (p>0.05). DMA was less toxic than iAs species to L. disperma and C. cf. dubia, but more toxic than AsIIIto Chlorella sp. CE-35. The toxicity of AsVto Chlorella sp. CE-35 and L. disperma decreased with increasing TP concentrations in the growth medium. Phosphate concentrations did not influence the toxicity of AsIIIto either organism. Chlorella sp. CE-35 showed the ability to reduce AsVto AsIII, indicating a substantial influence of phytoplankton on As biogeochemistry in freshwater aquatic systems. © 2014 Elsevier Inc.
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