Effect of initial cell density on the bioavailability and toxicity of copper in microalgal bioassays

被引:157
作者
Franklin, NM
Stauber, JL
Apte, SC
Lim, RP
机构
[1] CSIRO Energy Technol, Ctr Adv Analyt Chem, Bangor, NSW 2234, Australia
[2] Univ Technol Sydney, Dept Environm Sci, Broadway, NSW 2007, Australia
关键词
algae; copper; bioavailability; bioassay; flow cytometry;
D O I
10.1002/etc.5620210409
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
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 mug/L for Chlorella sp. and from 6.6 to 17 mug/L for S. capricornutum as the initial cell density increased from 102 to 105 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 104 to 101 algal cells/ml may seriously underestimate metal toxicity in natural waters.
引用
收藏
页码:742 / 751
页数:10
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