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The effect of pH on the uptake and toxicity of copper and zinc in a tropical freshwater alga (Chlorella sp.).
Arch Environ Contam Toxicol. 2006 Aug; 51(2):174-85.AE

Abstract

Copper and zinc toxicity to the freshwater alga Chlorella sp. was determined at a range of pH values (5.5-8.0) in a synthetic softwater (hardness 40-48 mg CaCO(3)/L). The effects of the metals on algal growth (cell division) rate were determined after 48-h exposure at pH 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. The toxicity of both metals was pH dependent. As pH decreased from 8.0 to 5.5, the copper concentration required to inhibit the algal growth rate by 50% (IC50) increased from 1.0 to 19 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) concentrations decreased with increasing pH, whereas toxicity was observed to increase. Measurements of extracellular (cell-bound) metal concentrations support the biotic ligand model (BLM) theory of competition between protons (H(+)) and metals for binding sites at the algal cell surface. Higher extracellular metal concentrations were observed at high pH, indicating reduced competition. Independent of pH, both extracellular and intracellular copper were directly related to growth inhibition in Chlorella sp., whereas zinc toxicity was related to cell-bound zinc only. These findings suggest that the algal cell surface may be considered as the biotic ligand in further development of a chronic BLM with microalgae. Conditional binding constants (log K) were determined experimentally (using measured intracellular metal concentrations) and theoretically (using concentration-response curves) for copper and zinc for Chlorella sp. at selected pH values. Excellent agreement was found indicating the possibility of using concentration-response data to estimate conditional metal-cell binding constants.

Authors+Show Affiliations

Institute for Nuclear Geophysiology, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, New South Wales, 2234, Australia, kwx@ansto.gov.auNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16583260

Citation

Wilde, Karyn L., et al. "The Effect of pH On the Uptake and Toxicity of Copper and Zinc in a Tropical Freshwater Alga (Chlorella Sp.)." Archives of Environmental Contamination and Toxicology, vol. 51, no. 2, 2006, pp. 174-85.
Wilde KL, Stauber JL, Markich SJ, et al. The effect of pH on the uptake and toxicity of copper and zinc in a tropical freshwater alga (Chlorella sp.). Arch Environ Contam Toxicol. 2006;51(2):174-85.
Wilde, K. L., Stauber, J. L., Markich, S. J., Franklin, N. M., & Brown, P. L. (2006). The effect of pH on the uptake and toxicity of copper and zinc in a tropical freshwater alga (Chlorella sp.). Archives of Environmental Contamination and Toxicology, 51(2), 174-85.
Wilde KL, et al. The Effect of pH On the Uptake and Toxicity of Copper and Zinc in a Tropical Freshwater Alga (Chlorella Sp.). Arch Environ Contam Toxicol. 2006;51(2):174-85. PubMed PMID: 16583260.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The effect of pH on the uptake and toxicity of copper and zinc in a tropical freshwater alga (Chlorella sp.). AU - Wilde,Karyn L, AU - Stauber,Jennifer L, AU - Markich,Scott J, AU - Franklin,Natasha M, AU - Brown,Paul L, Y1 - 2006/03/30/ PY - 2004/12/20/received PY - 2005/06/01/accepted PY - 2006/4/4/pubmed PY - 2006/9/9/medline PY - 2006/4/4/entrez SP - 174 EP - 85 JF - Archives of environmental contamination and toxicology JO - Arch Environ Contam Toxicol VL - 51 IS - 2 N2 - Copper and zinc toxicity to the freshwater alga Chlorella sp. was determined at a range of pH values (5.5-8.0) in a synthetic softwater (hardness 40-48 mg CaCO(3)/L). The effects of the metals on algal growth (cell division) rate were determined after 48-h exposure at pH 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. The toxicity of both metals was pH dependent. As pH decreased from 8.0 to 5.5, the copper concentration required to inhibit the algal growth rate by 50% (IC50) increased from 1.0 to 19 microg/L. For zinc, the IC50 increased from 52 to 2,700 microg/L over the same pH range. Changes in solution speciation alone did not explain the increased toxicity observed as the pH increased. Modelled Cu(2+) and Zn(2+) concentrations decreased with increasing pH, whereas toxicity was observed to increase. Measurements of extracellular (cell-bound) metal concentrations support the biotic ligand model (BLM) theory of competition between protons (H(+)) and metals for binding sites at the algal cell surface. Higher extracellular metal concentrations were observed at high pH, indicating reduced competition. Independent of pH, both extracellular and intracellular copper were directly related to growth inhibition in Chlorella sp., whereas zinc toxicity was related to cell-bound zinc only. These findings suggest that the algal cell surface may be considered as the biotic ligand in further development of a chronic BLM with microalgae. Conditional binding constants (log K) were determined experimentally (using measured intracellular metal concentrations) and theoretically (using concentration-response curves) for copper and zinc for Chlorella sp. at selected pH values. Excellent agreement was found indicating the possibility of using concentration-response data to estimate conditional metal-cell binding constants. SN - 0090-4341 UR - https://www.unboundmedicine.com/medline/citation/16583260/The_effect_of_pH_on_the_uptake_and_toxicity_of_copper_and_zinc_in_a_tropical_freshwater_alga__Chlorella_sp___ L2 - https://dx.doi.org/10.1007/s00244-004-0256-0 DB - PRIME DP - Unbound Medicine ER -