Probing the Relationship of Cyanobacterial Toxins and Reactive Oxygen Species Within the Natural World

The occurrence of harmful algal blooms (HABs) and their impacts on human health and the economy are only expected to worsen in the coming years, mainly due to climate change related factors. In Lake Wateree, SC, a HAB of the species Lyngbya wollei, has been persistent for more than 10 years and is estimated to occupy 60 - 90 km of shoreline. This natural laboratory provided and continues to provide a unique window into the chemistry and microbial ecology of HABs. Work in this dissertation was directed at answering a critical question: are biomass-to-toxin ratios constant in HABs? Initial work focused on analytical method development to identify and quantify the toxins produced by the Lyngbya wollei bloom in Lake Wateree. A series of method development steps was designed to refine the understanding of how algal-derived samples interact with analytical procedures. A method was established to increase method response and limit matrix-derived suppression interactions. Toxins produced by Lyngbya wollei include Lyngbya wollei toxins 1-6. The toxin production in three locations was monitored over 8 months, during the growing and following dormant season. Toxin production was normalized against total carbon, and the inorganic content of the Lyngbya wollei samples was recorded. Consideration of how biomass in grab samples correlates to the biomass of Lyngbya wollei and its toxins is presented. The second half of this manuscript demonstrates the importance of autoxidation processes on the rate and yield of hydrogen peroxide in natural waters. ROS are ubiquitous in natural waters; however, their concentrations are low (micromolar – attomolar concentrations) and their source in these waters is poorly understood. In the absence of photons, gallic acid was used as a source of hydrogen peroxide over a pH range of 5-9 and in natural waters collected from around South Carolina. The autoxidation of gallic acid was initiated by the reaction between gallic acid and dioxygen and propagated by superoxide through a free radical chain process. The addition of natural organic matter increased the rates of hydrogen peroxide production and gallic acid degradation. Results of this study suggest that 90% of hydrogen peroxide in natural waters may be tied to the autoxidation of natural organic matter