Materials and methods

using a green alga was applied to test the effects of a commercial formulation of atrazine. Test organism: Pseudokirchneriella subcapitata → single culture purchased from Canadian Phycological Culture Centre and grown in Bold's modified basal medium (Sigma-Aldrich) → non-motile, unicellular, crescent-shaped green algae → model organism → readily available and easily cultured → moderately sensitive to toxic substances and no clumping thus ideal for enumeration ●Atrazine is herbicide that inhibits photosynthesis and interferes with other enzymatic processes. It is currently a pesticide of major concern due to its possible negative effects on health (nausea, dizziness, increased ovarian cancer risk) , aquatic organisms, levels in drinking water and the development of resistance in some weeds as they mutate ● The goal for this experiment was to test the growth inhibition of Pseudokirchneriella (Selenastrum) subcapitata algae exposed to atrazine using the Environmental Canada algal growth inhibition test via the 96-well microplate technique. Eight concentrations of atrazine (ranging from 7.5-960 µg/L) were used with five replicates for each concentration with an initial cell density of 10,000 + 1000 cells/mL ● The endpoint for the reaction was absorbance of each well taken at 430 nm. ● The creation of a standard curve for cell concentration vs. absorbance was also a part of the experiment with five different cell densities ranging from 100- 1x106 cells/mL. ● The hypothesis was correct in ascertaining Results Figure 4: A first-order linear regression for cell concentration vs. absorbance at 430 nm for five serial dilutions. Cells were enumerated using a hemocytometer. Figure 1: P. Subcapitata cell