OBJECTIVES:To evaluate the remediation efficiency of Mucor hiemalis by comparing media elimination, uptake, and biotransformation of microcystin-LR with exposure to pure toxin versus a crude bloom extract. RESULTS:With exposure to the extract, the elimination rate of microcystin-LR from the media, which was 0.28 ng MC-LR l-1 h-1, was significantly higher compared to that achieved with exposure to the pure toxin (0.16 ng MC-LR l-1 h-1) after 24 h. However, intracellular breakdown of microcystin-LR was significantly lower in the extract exposed pellets compared to the pure toxin treated fungal pellets over time. This coincided with reduced intracellular glutathione S-transferase activity with crude extract exposure which could be responsible for the detection of only the glutathione conjugate of microcystin-LR. CONCLUSION:This paper signifies the importance of using laboratory exposure scenarios which resemble conditions in nature to fully understand and evaluate remediation efficiency. There is merit in using M. hiemalis for mycoremediation of cyanotoxins in surface waters.