|This thesis explored the ways in which cyanobacterial communities respond to three common nitrogen forms (i.e., nitrate, ammonium, and urea) via two field experiments. Chapter I describes a field experiment that demonstrated the preference of cyanobacterial communities to reduced forms of nitrogen (i.e., ammonium and urea) that was observed through high uptake and removal from the water column. Chapter II delves into how the cyanobacteria are using the nitrogen that was being introduced and showed that when excess concentrations of reduced nitrogen enter the water column, cyanobacteria quickly incorporate the nitrogen into phycocyanin pigments as a means of nitrogen storage. Then, once the environment is devoid of nitrogen, the cyanobacteria will begin degrading the phycocyanin pigments as a nitrogen source. Results also showed, on average, that reduced nitrogen forms promote more cells, a longer peak bloom period, and more toxins.