CADMIUM AND ZINC BIOAVAILABILITY TO <i>SELENASTRUM CAPRICORNUTUM</i> (CHLOROPHYCEAE): ACCIDENTAL METAL UPTAKE AND TOXICITY IN THE PRESENCE OF CITRATE

Errécalde, Olivier; Campbell, Peter G. C.

doi:10.1046/j.1529-8817.2000.99103.x

Cited by 71 publications

(70 citation statements)

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“…The algae were then washed with 10 ml of a Na 2 EDTA solution (100 µM) for 10 min, and further rinsed 3 to 4 times with 0.22 µm-filtered deionized water, after which the radioactivity of the intracellular metals in the cells was counted. The EDTA washing technique can efficiently remove metals bound to the surface of the algal cells (Bates et al 1982, Errecalde & Campbell 2000. The efficiency of EDTA washing in removing extracellular Se was, however, unknown and was not tested in this study.…”

Section: Methodsmentioning

confidence: 97%

Biological uptake of Cd, Se(IV) and Zn by Chlamydomonas reinhardtii in response to different phosphate and nitrate additions

Wang

2004

Aquat. Microb. Ecol.

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We investigated the influences of different nutrient regimes on the accumulation of Cd, Zn, and Se(IV) in the freshwater green alga Chlamydomonas reinhardtii over a 4 h exposure period. After the cells had been acclimated to different ambient P levels from 0.1 to 10.0 µM for 2 d in different media (buffer, basic and simplified uptake media), their intracellular metal concentrations increased by 3.6 to 14× for Cd and 1.6 to 4.0× for Zn. Se uptake was, however, decreased by 7.7 to 44×. Semi-continuous culture experiments further demonstrated that the alga's metal concentrations were enhanced 26× for Cd and 8.0× for Zn, whereas Se accumulation was inhibited 75× at the same medium P levels. The uptake rates in semi-continuous cultures increased by 269× for Cd and 11× for Zn, but Se uptake decreased 92× with increasing P concentration. Medium P additions also significantly increased intracellular partitioning for Cd and Zn, but there was no apparent effect for Se. For P-starved or P-repleted cells, the P-enriched medium dramatically increased the cellular accumulation of Cd and Zn compared with the P-depleted medium. A surge uptake of Cd and Zn occurred in P-starved cells. P starvation also resulted in a remarkable increase in Se accumulation in the Pdeplete medium. N enrichment from 5 to 200 µM significantly increased the alga's uptake and intracellular partitioning for Cd and Zn, although the effects were not strictly concentration-dependent. Our study strongly suggests that ambient P enrichment greatly stimulates Cd and Zn accumulation and sequestration in C. reinhardtii, presumably due to rapid P uptake and subsequent formation of polyphosphate in the cells, and distinctly inhibits Se uptake possibly due to the competition of similar anionic forms for transport between Se and P. KEY WORDS: Uptake · Metals · Green alga · Nutrient enrichment Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 35: [163][164][165][166][167][168][169][170][171][172][173] 2004 concentrations in phytoplankton, especially in freshwater species, although this may be important in understanding the stoichiometric mechanisms in lake systems.Under N-limited conditions, a significant reduction in photosynthetic activity occurs in green algae, including a sharp decline in their chlorophyll content and a rise in carotenoid concentration (Sayed 1998, Hanagata & Dubinsky 1999. When the phytoplankton are under P-limited conditions, the uptake system for phosphate in cells is highly activated. Abrupt exogenous P enrichment results in a rapid P incorporation and storage in intracellular polyphosphates (Kulaev & Vagabov 1983, Wagner & Falkner 2001. Polyphosphate bodies are considered an important pool for the sequestration of heavy metals by freshwater phytoplankton (e.g. Cd, Hg, Pb, and Zn) (Jensen et al. 1982a). Although metal limitation (e.g. of Fe) in phytoplankton may affect the assimilation of nitrate and phosphate (McKay et al. 2001), the effects of nutrient enrichment or starvation on m...

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Section: Methodsmentioning

confidence: 97%

Biological uptake of Cd, Se(IV) and Zn by Chlamydomonas reinhardtii in response to different phosphate and nitrate additions

Wang

2004

Aquat. Microb. Ecol.

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“…Ligand-metal complexes of these types are potentially able to cross cell membranes, leading to an increase in toxicity above that expected on the basis of the free-ion concentration (Poldoski, 1979;Block and Pärt, 1986;Guy and Kean, 1980;Pärt and Wikmark, 1984;Daly et al, 1990;Errécalde et al, 1998;Errécalde and Campbell, 2000).…”

Section: Design Of the Assay Conditionsmentioning

confidence: 99%

Coupling the use of computer chemical speciation models and culture techniques in laboratory investigations of trace metal toxicity

Twiss

Errécalde²,

Fortin

et al. 2001

Chemical Speciation & Bioavailability

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Chemical Speciation and Bioavailability (2001), 13(1) ABSTRACTThe bioavailability and toxicity of a dissolved metal are closely linked to the metal's chemical speciation in solution. A variety of inorganic and organic ligands are often used in laboratory toxicity tests to control the concentration of labile trace metal in solution. Computerised chemical speciation models based on thermodynamic principles can be used to estimate metal speciation under such experimental conditions. However, these models are sensitive to the quality of their thermodynamic databases. Detailed protocols for the incorporation of reliable equilibrium formation constants into widely available computer chemical speciation programs (e.g., MINEQL+ and MINTEQ) are provided. The examples demonstrate both the benefits and the potential pitfalls involved in the use of chemical speciation models. The application of chemical speciation modelling to metal toxicity studies is discussed and guidelines are proposed for its proper use. Both defined media and chemical speciation programs have co-existed for two decades but the combined use of these techniques has been reserved for those possessing in-depth knowledge of both chemistry and biology. The techniques presented should enable an investigator with basic biological, chemical and computing skills to design an aqueous medium and incorporate correct thermodynamic constants into a computer chemical speciation program, starting from a standardised database, thereby providing a sound framework for critically assessing the biological response of a particular test organism to a given metal.

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“…The most important approaches include the free ion activity model (FIAM) (Morel, 1983;McLaughlin et al, 1997;Hudson, 1998; 0045-6535/$ -see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2004.11.056 Errécalde and Campbell, 2000), the correlation between the labile metals in soil pools determined by single or sequential extraction methods and their accumulation in plants (Haq et al, 1980;Novozamsky et al, 1993;Shan et al, 2003), the isotope dilution exchange method (Collins et al, 2003) and the diffusive gradients in thin films (DGT) (Zhang et al, , 2001.…”

Section: Introductionmentioning

confidence: 99%

Comparison of a rhizosphere-based method with other one-step extraction methods for assessing the bioavailability of soil metals to wheat

et al. 2005

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There is no method recognized as a universal approach for evaluation of bioavailability of heavy metals in soil. Based on the simulation of the rhizosphere soil conditions and integration of the combined effects of root-soil interactions as a whole, a rhizosphere-based method has been proposed. Wet fresh rhizosphere soil was extracted by lowmolecular-weight organic acids (LMWOAs) to fractionate metal fractions of soil pools, which were then correlated with the metal contents of wheat roots and shoots. The rhizosphere-based method was compared with other one-step extraction methods using DTPA, EDTA, CaCl 2 , and NaNO 3 as extractants and the first step of the Community Bureau of Reference (BCR) method. Simple correlation and stepwise multiple regression analysis were used for the comparison. Simple correlation indicated that the extractable Cu, Zn, Cr, and Cd of soils by the rhizosphere-based method were significantly correlated with the metal contents of wheat roots. For DTPA, BCR1 and EDTA methods there was a relatively poor correlation between the extractable Cu, Zn and Cd of soil and metal contents of wheat roots. Stepwise multiple regression analysis revealed that the equation of the rhizosphere-based method was the simplest one, and no soil properties variables needed to be added. In contrast, the equations of other one-step extraction methods were more complicated, and soil properties variables needed to be entered. The most distinct feature of the rhizosphere-based method was that the recommended method was suitable for acidic, neutral and near alkaline soils. However, the DTPA and EDTA extraction methods were suitable for calcareous soils only-or-only for acidic soils. The CaCl 2 , and NaNO 3 extraction methods were only suitable for exchangeable metals. In short, the rhizosphere-based method was the most robust approach for evaluation of bioavailability of heavy metals in soils to wheat.

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CADMIUM AND ZINC BIOAVAILABILITY TO SELENASTRUM CAPRICORNUTUM (CHLOROPHYCEAE): ACCIDENTAL METAL UPTAKE AND TOXICITY IN THE PRESENCE OF CITRATE

Cited by 71 publications

References 25 publications

Biological uptake of Cd, Se(IV) and Zn by Chlamydomonas reinhardtii in response to different phosphate and nitrate additions

Biological uptake of Cd, Se(IV) and Zn by Chlamydomonas reinhardtii in response to different phosphate and nitrate additions

Coupling the use of computer chemical speciation models and culture techniques in laboratory investigations of trace metal toxicity

Comparison of a rhizosphere-based method with other one-step extraction methods for assessing the bioavailability of soil metals to wheat

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