Microplastic pollution is an alarming issue, and the potential toxicological effects of microplastic leachates warrant investigation. In this experiment, researchers sought to quantify the effect of leachate from polyethylene terephthalate (PET) microplastic powder—irradiated for varying degrees of time— on Clamydamonous reinhardtii cultures’ optical density. Preliminary experimentation demonstrated that the physical presence of PET microplastic powder generated a significant inhibitory effect on observed growth rate, so this study investigated the effects of PET microplastic leachate isolated from PET powder. Researchers predicted that plastic exposed to higher degrees of irradiation would produce a larger concentration of leachate, and in turn, a greater level of irradiation would produce a greater inhibitory effect. However, the results of the experiment yielded no statistical difference in culture density among experimental groups. This indicates that the concentration of leachate in each solution was insufficient, or conversely, this nullifies the predicted significance of the toxicological properties of PET leachate. Researchers favor the former explanation; antimony is known to be a toxic leachate compound derived from PET— thus, a sufficient concentration would likely produce an inhibitory effect. Even though a significant difference in optical culture density wasn’t observed, over the course of the experiment, qualitative observations of C.reinhardtii’s colonization behavior demonstrated the potentially detrimental trophic-level effects of plastic pollution. Both the effect of enhanced leachate exposure and the trophic-level implications of pollution exemplify environmentally significant discoveries worthy of future investigation.