title: Development of flow cytometry-based algal bioassays for assessing toxicity of copper in natural waters.
abstract: Copper toxicity to the freshwater algae Selenastrum capricornutum and Chlorella sp. and the marine algae Phaeodactylum tricornutum and Dunaliella tertiolecta was investigated using different parameters measured by flow cytometry: cell division rate inhibition, chlorophyll a fluorescence, cell size (i.e., light-scattering), and enzyme activity. These parameters were assessed regarding their usefulness as alternative endpoints for acute (1-24 h) and chronic (48-72 h) toxicity tests. At copper concentrations of 10 micrograms/L or less, significant inhibition (50%) of the cell division rate was observed after 48- and 72-h exposures for Chlorella sp., S. capricornutum, and P. tricornutum. Bioassays based on increases in algal cell size were also sensitive for Chlorella sp. and P. tricornutum. Copper caused both chlorophyll a fluorescence stimulation (48-h EC50 of 10 +/- 1 micrograms Cu/L for P. tricornutum) and inhibition (48-h EC50 of 14 +/- 6 micrograms Cu/L for S. capricornutum). For acute toxicity over short exposure periods, esterase activity in S. capricornutum using fluorescein diacetate offered a rapid alternative (3-h EC50 of 90 +/- 40 micrograms Cu/L) to growth inhibition tests for monitoring copper toxicity in mine-impacted waters. For all the effect parameters measured, D. tertiolecta was tolerant to copper at concentrations up to its solubility limit in seawater. These results demonstrate that flow cytometry is a useful technique for toxicity testing with microalgae and provide additional information regarding the general mode of action of copper (II) to algal species.
authors.affiliation: Centre for Advanced Analytical Chemistry, CSIRO Energy Technology, PMB 7, Bangor, New South Wales 2234, Australia. natasha.franklin@det.csiro.au
authors.forename: N M
authors.initials: NM
authors.lastname: Franklin
authors.forename: J L
authors.initials: JL
authors.lastname: Stauber
authors.forename: R P
authors.initials: RP
authors.lastname: Lim
mesh_terms: D001681:Biological Assay; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002734:Chlorophyll / Q000032:analysis / Q000378:metabolism; D003300:Copper / Q000633:toxicity*; D023381:Endpoint Determination; D056890:Eukaryota / Q000378:metabolism* / Q000648:ultrastructure; D005434:Flow Cytometry; D005453:Fluorescence; D005618:Fresh Water; D008386:Marine Biology; D008564:Membrane Potentials / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D003300:Copper