Date of Award


Document Type

Campus Access Thesis


Marine Science

First Advisor

James L. Pinckney


Kiawah Island is a rapidly growing coastal community located south of Charleston, SC. Best management practices mandate stormwater detention ponds to moderate the impacts of development. The detention pond network is subject to high levels of nitrogen and phosphorus loading from golf course, residential, and road runoff, atmospheric inputs, wildlife waste, and oceanic inputs. This system is characterized by eutrophic conditions and recurrent water quality problems (hypoxia and anoxia, fish kills, and harmful algal blooms). Cyanobacterial blooms (Microcystis aeruginosa, Anabaena sp, and Oscillatoria sp.) are common in the summer and late fall in this region, and nitrogen loading has been implicated as the cause. The purpose of this study was to quantify the growth of planktonic cyanobacteria in response to manipulations of the nitrogen to phosphorus ratio and form of nitrogen (NO3, NH4, urea, or combination). Nutrient bioassays were performed in situ monthly (June to September 2009) in two detention ponds K61 and K67. Urea additions resulted in significantly greater cyanobacterial biomass than the control or other nitrogen forms in pond K61. NO3 additions promoted cyanobacterial growth in pond K61. The molar DIN:DIP ratio averaged 0.15 over the sampling period but the relationship between cyanobacterial biomass and DIN:DIP was not significant. The different response to nitrogen treatments observed at the two study sites may reflect differences in the cyanobacteria community composition at each study site. The importance of NO3 as a nitrogen source for cyanobacteria is well documented; however, the importance of organic nitrogen for cyanobacterial growth has not been documented in this system.