This project focuses on the effect of surface chemistry on the interactions of graphene oxide (GO) and carbon nanotubes (CNTs) with Microcystis aeruginosa, a freshwater cyanobacteria species. A dose-response was done using concentrations of 0 to 100 µg/mL. Results indicate that at 11, 76, and 126 µg/mL, GO, TGO200 and TGO500 decrease chlorophyll content by 50% (EC50), respectively. For CNT, the EC50 was 7 µg/mL after a 96h exposure. Chlorophyll a content is shown to be less affected as the annealing on GO materials increase. These results provide insight into the effects of surface chemistry on the toxicity of GO, and CNTs, which will allow for a safe design of carbon-based nanotechnologies.