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Toward a biotic ligand model for freshwater green algae: surface-bound and internal copper are better predictors of toxicity than free Cu2+-ion activity when pH is varied

Karel De Schamphelaere (UGent) , Jennifer L Stauber, Karyn L Wilde, Scott J Markich, Paul L Brown, Natasha M Franklin, Nicola M Creighton and Colin Janssen (UGent)
(2005) ENVIRONMENTAL SCIENCE & TECHNOLOGY. 39(7). p.2067-2072
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Abstract
The freshwater green microalgae Chlorella sp. and Pseudokirchneriella subcapitata (P. subcapitata) were chronically (48 and 72 h, respectively) exposed to copper at various pH levels, i.e., pH 6-7.5 and pH 5.9-8.5, respectively. Concentrations resulting in 50% inhibition of exponential growth rate (EC50) were determined as dissolved Cu, estimated chemical activity of the free Cu2+ ion (as pCu = - log{Cu2+ activity as molarity}), and as external (surface-bound) Cu and internal Cu in the algal cells. With increasing pH, EC50(dissolved) decreased from 30 to 1.1 mu g of Cu L-1 for Chlorella sp. and from 46 to 18 mu g of Cu L-1 for P. subcapitata. The pH effect on copper toxicity was even more obvious when expressed as Cu2+ activity. The EC50(pCu) increased on average 1.4 pCu unit per pH unit for Chlorella sp. and 1.1 pCu unit per pH unit for P. subcapitata, thus indicating a marked increase of Cu2+ toxicity at higher pH (more than 1 order of magnitude per pH unit). In contrast, it was found that EC50 values expressed as surface bound or external copper (EC50(external)) and as internal copper (EC50(internal)) did not vary substantially when pH was increased. External Cu was operationally defined as the Cu fraction removable from the algal cell by short-term contact with ethylenediaminetetraacetic acid; internal copper was defined as the nonremovable fraction. For Chlorella, sp. the EC50(external) varied between 5 and 10 fg of Cu/ cell (factor of 2 difference) and the EC50(internal) between 25 and 40 fg of Cu/cell (factor of 1.6 difference). For P. subcapitata the EC50(external) varied between 10 and 28 fg of Cu/cell (factor of 2.8 difference) and the EC50internal between 42 and 71 fg of Cu/cell (factor of 1.7 difference). Because the observed variation in EC50(external) and EC50(internal) is much less than the variation in EC50(Cu)(2+), it is concluded that both external and internal copper are better predictors of copper toxicity than Cu2+ when pH is varied. From the perspective of toxicity modeling, this observation is the first step toward considering the use of the cell surface as the algal biotic ligand for Cu in a similar way as fish gills fulfill this role in the biotic ligand model for predicting metal toxicity to fish species.
Keywords
BIOAVAILABILITY, TROUT ONCORHYNCHUS-MYKISS, BINDING, ZINC TOXICITY, METAL TOXICITY, FIELD VALIDATION, PSEUDOKIRCHNERIELLA-SUBCAPITATA, RAINBOW-TROUT, DAPHNIA-MAGNA, FREE-ION ACTIVITY

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MLA
De Schamphelaere, Karel, et al. “Toward a Biotic Ligand Model for Freshwater Green Algae: Surface-Bound and Internal Copper Are Better Predictors of Toxicity than Free Cu2+-Ion Activity When PH Is Varied.” ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol. 39, no. 7, 2005, pp. 2067–72, doi:10.1021/es049256l.
APA
De Schamphelaere, K., Stauber, J. L., Wilde, K. L., Markich, S. J., Brown, P. L., Franklin, N. M., … Janssen, C. (2005). Toward a biotic ligand model for freshwater green algae: surface-bound and internal copper are better predictors of toxicity than free Cu2+-ion activity when pH is varied. ENVIRONMENTAL SCIENCE & TECHNOLOGY, 39(7), 2067–2072. https://doi.org/10.1021/es049256l
Chicago author-date
De Schamphelaere, Karel, Jennifer L Stauber, Karyn L Wilde, Scott J Markich, Paul L Brown, Natasha M Franklin, Nicola M Creighton, and Colin Janssen. 2005. “Toward a Biotic Ligand Model for Freshwater Green Algae: Surface-Bound and Internal Copper Are Better Predictors of Toxicity than Free Cu2+-Ion Activity When PH Is Varied.” ENVIRONMENTAL SCIENCE & TECHNOLOGY 39 (7): 2067–72. https://doi.org/10.1021/es049256l.
Chicago author-date (all authors)
De Schamphelaere, Karel, Jennifer L Stauber, Karyn L Wilde, Scott J Markich, Paul L Brown, Natasha M Franklin, Nicola M Creighton, and Colin Janssen. 2005. “Toward a Biotic Ligand Model for Freshwater Green Algae: Surface-Bound and Internal Copper Are Better Predictors of Toxicity than Free Cu2+-Ion Activity When PH Is Varied.” ENVIRONMENTAL SCIENCE & TECHNOLOGY 39 (7): 2067–2072. doi:10.1021/es049256l.
Vancouver
1.
De Schamphelaere K, Stauber JL, Wilde KL, Markich SJ, Brown PL, Franklin NM, et al. Toward a biotic ligand model for freshwater green algae: surface-bound and internal copper are better predictors of toxicity than free Cu2+-ion activity when pH is varied. ENVIRONMENTAL SCIENCE & TECHNOLOGY. 2005;39(7):2067–72.
IEEE
[1]
K. De Schamphelaere et al., “Toward a biotic ligand model for freshwater green algae: surface-bound and internal copper are better predictors of toxicity than free Cu2+-ion activity when pH is varied,” ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol. 39, no. 7, pp. 2067–2072, 2005.
@article{306287,
  abstract     = {{The freshwater green microalgae Chlorella sp. and Pseudokirchneriella subcapitata (P. subcapitata) were chronically (48 and 72 h, respectively) exposed to copper at various pH levels, i.e., pH 6-7.5 and pH 5.9-8.5, respectively. Concentrations resulting in 50% inhibition of exponential growth rate (EC50) were determined as dissolved Cu, estimated chemical activity of the free Cu2+ ion (as pCu = - log{Cu2+ activity as molarity}), and as external (surface-bound) Cu and internal Cu in the algal cells. With increasing pH, EC50(dissolved) decreased from 30 to 1.1 mu g of Cu L-1 for Chlorella sp. and from 46 to 18 mu g of Cu L-1 for P. subcapitata. The pH effect on copper toxicity was even more obvious when expressed as Cu2+ activity. The EC50(pCu) increased on average 1.4 pCu unit per pH unit for Chlorella sp. and 1.1 pCu unit per pH unit for P. subcapitata, thus indicating a marked increase of Cu2+ toxicity at higher pH (more than 1 order of magnitude per pH unit). In contrast, it was found that EC50 values expressed as surface bound or external copper (EC50(external)) and as internal copper (EC50(internal)) did not vary substantially when pH was increased. External Cu was operationally defined as the Cu fraction removable from the algal cell by short-term contact with ethylenediaminetetraacetic acid; internal copper was defined as the nonremovable fraction. For Chlorella, sp. the EC50(external) varied between 5 and 10 fg of Cu/ cell (factor of 2 difference) and the EC50(internal) between 25 and 40 fg of Cu/cell (factor of 1.6 difference). For P. subcapitata the EC50(external) varied between 10 and 28 fg of Cu/cell (factor of 2.8 difference) and the EC50internal between 42 and 71 fg of Cu/cell (factor of 1.7 difference). Because the observed variation in EC50(external) and EC50(internal) is much less than the variation in EC50(Cu)(2+), it is concluded that both external and internal copper are better predictors of copper toxicity than Cu2+ when pH is varied. From the perspective of toxicity modeling, this observation is the first step toward considering the use of the cell surface as the algal biotic ligand for Cu in a similar way as fish gills fulfill this role in the biotic ligand model for predicting metal toxicity to fish species.}},
  author       = {{De Schamphelaere, Karel and Stauber, Jennifer L and Wilde, Karyn L and Markich, Scott J and Brown, Paul L and Franklin, Natasha M and Creighton, Nicola M and Janssen, Colin}},
  issn         = {{0013-936X}},
  journal      = {{ENVIRONMENTAL SCIENCE & TECHNOLOGY}},
  keywords     = {{BIOAVAILABILITY,TROUT ONCORHYNCHUS-MYKISS,BINDING,ZINC TOXICITY,METAL TOXICITY,FIELD VALIDATION,PSEUDOKIRCHNERIELLA-SUBCAPITATA,RAINBOW-TROUT,DAPHNIA-MAGNA,FREE-ION ACTIVITY}},
  language     = {{eng}},
  number       = {{7}},
  pages        = {{2067--2072}},
  title        = {{Toward a biotic ligand model for freshwater green algae: surface-bound and internal copper are better predictors of toxicity than free Cu2+-ion activity when pH is varied}},
  url          = {{http://doi.org/10.1021/es049256l}},
  volume       = {{39}},
  year         = {{2005}},
}
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