Comparative assessment of herbicide phytotoxicity to Selenastrum capricornutum using microplate and flask bioassay procedures

Abstract

Four reference toxicants (Cr6+, Cu2+, Zn2+, phenol) and 9 herbicides (imazamethabenz, 2,4‐dichlorophenoxyacetic acid, picloram, glyphosate, bromoxynil, metolachlor, diquat dibromide, hexazinone, cyanazine) were appraised using both the microplate and flask assay Ninety‐six hour EC50s determined with Selenastrum capricornutum as the indicator species essentially demonstrated good intermethodological data concordance for all chemicals, with the exception of diquat dibromide, whose phytotoxicity in the microplate assay (EC50 = 4.9 μg · L−1) was nearly 7 times that of the flask assay (EC50 = 34.2 μg · L−1). Comparisons with other data in the scientific literature relating to similar herbicides with the same or different green algal indicator species appeared to corroborate the overall data obtained in our study. More than 4 orders of magnitude separated the most toxic (cyanazine, flask, and microplate EC50s of 17.6 and 16.9 μg · L−1, respectively) and the least toxic (imazamethabenz, flask, and microplate EC50s of 89.1 and 91.1 mg · L−1, respectively) herbicides. The biprocedural phytotoxicity comparison described in this work suggests that the simpler algal microplate assay can be an appropriate alternative to the flask technique to evaluate the algal growth inhibition effects of herbicides.

Comparative Sensitivity of Five Species of Macrophytes and Six Species of Algae to Atrazine, Metribuzin, Alachlor, and Metolachlor

“…St-Laurent et al [4] found that Selenastrum was sensitive to metolachlor at 55 g/L (EC50), which is comparable to our 96-h EC50 of 84 g/L. St-Laurent et al [4] found that Selenastrum was sensitive to metolachlor at 55 g/L (EC50), which is comparable to our 96-h EC50 of 84 g/L.…”

Biological effects of PPCPs on aquatic lives and evaluation of river waters affected by different wastewater treatment levels

“…We used the Algal Growth Inhibition (AGI) test, in which PPCP samples were exposed to algae (Pseudokirchneriella subcapitata (NIES-35)) in a 96-hole microplate following the standard procedure (Blaise et al 1986;St-Laurent et al 1992) with minor modification (Yamashita et al 2006). For exposure of PPCP samples, dilution series (maximum concentration 10 mg/L) was prepared by serial 1:1 dilution with culture medium in 10 steps.…”

Microplates as a microreactor platform for microalgae research

“…Efforts to standardize these assays have been made by international organizations (i.e., ISO, US EPA, and OECD) . Despite these efforts, several authors recommend improving gas‐exchange conditions and limiting the assay to the central part of the plate . However, there are no reports on descriptive or statistical validation of the microplate system for kinetic characterization of microalgae cultures.…”