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Effect of initial cell density on the bioavailability and toxicity of copper in microalgal bioassays.
Environ Toxicol Chem. 2002 Apr; 21(4):742-51.ET

Abstract

Algal toxicity tests based on growth inhibition over 72 h have been extensively used to assess the toxicity of contaminants in natural waters. However, these laboratory tests use high cell densities compared to those found in aquatic systems in order to obtain a measurable algal response. The high cell densities and test duration can result in changes in chemical speciation, bioavailability, and toxicity of contaminants throughout the test. With the recent application of flow cytometry to ecotoxicology, it is now possible to use lower initial cell densities to minimize chemical speciation changes. The speciation and toxicity of copper in static bioassays with the tropical freshwater alga Chlorella sp. and the temperate species Selenastrum capricornutum (Pseudokirchneriella subcapitata) were investigated at a range of initial cell densities (10(2)-10(5) cells/ml). Copper toxicity decreased with increasing initial cell density. Copper concentrations required to inhibit growth (cell division) rate by 50% (72-h median effective concentration [EC50]) increased from 4.6 to 16 microg/L for Chlorella sp. and from 6.6 to 17 microg/L for S. capricornutum as the initial cell density increased from 10(2) to 10(5) cells/ml. Measurements of anodic stripping voltammetry-labile, extracellular, and intracellular copper confirmed that at higher initial cell densities, less copper was bound to the cells, resulting in less copper uptake and lower toxicity. Chemical measurements indicated that reduced copper toxicity was due primarily to depletion of dissolved copper in solution, with solution speciation changes due to algal exudates and pH playing a minor role. These findings suggest that standard static laboratory bioassays using 10(4) to 10(5) algal cells/ml may seriously underestimate metal toxicity in natural waters.

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Authors+Show Affiliations

Franklin NM
Centre for Advanced Analytical Chemistry, CSIRO Energy Technology, Bangor, New South Wales, Australia. natasha.franklin@csiro.au
Stauber JL
No affiliation info available
Apte SC
No affiliation info available
Lim RP
No affiliation info available

MeSH

Biological AvailabilityCell DivisionChlorophytaCopperFlow CytometryPopulation DynamicsReproducibility of ResultsSensitivity and SpecificityToxicity TestsWater Pollutants

Pub Type(s)

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

Language

eng

PubMed ID

11951947

Citation

Franklin, Natasha M., et al. "Effect of Initial Cell Density On the Bioavailability and Toxicity of Copper in Microalgal Bioassays." Environmental Toxicology and Chemistry, vol. 21, no. 4, 2002, pp. 742-51.
Franklin NM, Stauber JL, Apte SC, et al. Effect of initial cell density on the bioavailability and toxicity of copper in microalgal bioassays. Environ Toxicol Chem. 2002;21(4):742-51.
Franklin, N. M., Stauber, J. L., Apte, S. C., & Lim, R. P. (2002). Effect of initial cell density on the bioavailability and toxicity of copper in microalgal bioassays. Environmental Toxicology and Chemistry, 21(4), 742-51.
Franklin NM, et al. Effect of Initial Cell Density On the Bioavailability and Toxicity of Copper in Microalgal Bioassays. Environ Toxicol Chem. 2002;21(4):742-51. PubMed PMID: 11951947.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of initial cell density on the bioavailability and toxicity of copper in microalgal bioassays. AU - Franklin,Natasha M, AU - Stauber,Jennifer L, AU - Apte,Simon C, AU - Lim,Richard P, PY - 2002/4/16/pubmed PY - 2002/10/3/medline PY - 2002/4/16/entrez SP - 742 EP - 51 JF - Environmental toxicology and chemistry JO - Environ Toxicol Chem VL - 21 IS - 4 N2 - Algal toxicity tests based on growth inhibition over 72 h have been extensively used to assess the toxicity of contaminants in natural waters. However, these laboratory tests use high cell densities compared to those found in aquatic systems in order to obtain a measurable algal response. The high cell densities and test duration can result in changes in chemical speciation, bioavailability, and toxicity of contaminants throughout the test. With the recent application of flow cytometry to ecotoxicology, it is now possible to use lower initial cell densities to minimize chemical speciation changes. The speciation and toxicity of copper in static bioassays with the tropical freshwater alga Chlorella sp. and the temperate species Selenastrum capricornutum (Pseudokirchneriella subcapitata) were investigated at a range of initial cell densities (10(2)-10(5) cells/ml). Copper toxicity decreased with increasing initial cell density. Copper concentrations required to inhibit growth (cell division) rate by 50% (72-h median effective concentration [EC50]) increased from 4.6 to 16 microg/L for Chlorella sp. and from 6.6 to 17 microg/L for S. capricornutum as the initial cell density increased from 10(2) to 10(5) cells/ml. Measurements of anodic stripping voltammetry-labile, extracellular, and intracellular copper confirmed that at higher initial cell densities, less copper was bound to the cells, resulting in less copper uptake and lower toxicity. Chemical measurements indicated that reduced copper toxicity was due primarily to depletion of dissolved copper in solution, with solution speciation changes due to algal exudates and pH playing a minor role. These findings suggest that standard static laboratory bioassays using 10(4) to 10(5) algal cells/ml may seriously underestimate metal toxicity in natural waters. SN - 0730-7268 UR - https://www.unboundmedicine.com/medline/citation/11951947/Effect_of_initial_cell_density_on_the_bioavailability_and_toxicity_of_copper_in_microalgal_bioassays_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0730-7268&date=2002&volume=21&issue=4&spage=742 DB - PRIME DP - Unbound Medicine ER -