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Modifications to the algal growth inhibition test for use as a regulatory assay
Author(s) -
Geis Steven W.,
Fleming Kari L.,
Korthals Eric T.,
Searle Greg,
Reynolds Lou,
Karner Dawn A.
Publication year - 2000
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620190105
Subject(s) - selenastrum , bioassay , macrophyte , algae , biology , replicate , hemocytometer , erlenmeyer flask , aquatic toxicology , chlorophyta , colorimetry , environmental chemistry , toxicology , chromatography , toxicity , chemistry , botany , ecology , mathematics , biochemistry , statistics , organic chemistry
Biological assays using aquatic invertebrates and fish do not necessarily predict protection levels for primary producers such as algae and aquatic macrophytes. State regulatory programs may not be protecting the environment from many phytotoxic compounds. Recent modifications of the U.S. Environmental Protection Agency's algal test were evaluated for their potential use as a regulatory assay. Primary goals of this investigation were to downsize the algal assay and to evaluate various methods of automation. Disposable microplates with 2‐ml sample wells were evaluated as an alternative testing chamber for the 96‐h growth inhibition test with Raphidocelis subcapitata (formerly known as Selenastrum capricornutum ). We compared the standardized Erlenmeyer® flask test to the microplate test using CuCl 2 , NaCl, phenol, ZnCl 2 , and a surfactant. We noted improved control performance with the microplate test, whereas median inhibitory concentration values were similar for both methods. Other procedures we addressed included the use of EDTA, filtration of samples, and the effect of colored samples on algal growth. We also evaluated growth estimates by comparing manual cell counting to more automated growth estimates using fluorescence and ab‐sorbance endpoints. The use of fluorescence and absorbance measurements demonstrated reductions in replicate variability over manual counting and may offer time‐saving alternatives for laboratory analysts.