Year

2014

Season

Summer

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)

Department

Biology

NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Cliff Ross

Second Advisor

Dr. Dale A. Casamatta

Third Advisor

Dr. Michael R. Lentz

Department Chair

Dr. Dan Moon

College Dean

Dr. Barbara A. Hetrick

Abstract

Harmful algal blooms (HABs) are found worldwide, particularly in places where warm, well-lit, and stagnant waters are common. HABs can have negative effects on aquatic plants and wildlife due to the reduction in light availability associated with turbidity, decrease in O2 availability, and the production of secondary metabolites that can harm or even prove lethal. Aquatic ecosystems are regularly being affected by elevated salinity because of recent water management strategies, episodes of drought, and salt water intrusion. This research focused on how salinity levels ranging from 0-10ppt affected physiological attributes such as cellular growth and abundance, cell mortality, toxin release, and oxidative stress in the toxigenic cyanobacterium, Microcystis aeruginosa. It was determined that salinity treatments of 7ppt and above caused a decrease in both cellular growth and abundance, as well as an increase in toxin release due to cell mortality. M. aeruginosa was able to survive in salinities up to 7ppt. A pattern of caspase activity in response to elevated salinity was shown, but whether cellular mortality was due solely to programmed cell death (PCD) was not definitive. A strong antioxidant response, measured through catalase activity, was noted when salinity was enhanced to 7ppt. Above this value, the damaging effects of salinity caused elevated levels of reactive oxygen species (ROS) production and cell death. It was determined that the maximum amount of hydrogen peroxide that M. aeruginosa could withstand without significant impact to growth and abundance was below 250µM. Salinities of 7ppt and above had a negative impact on the physiology of M. aeruginosa, leading to cell death and an increase in microcystin release into the environment. These two factors can lead to fish kills, poor drinking water, and other recreational and commercial problems for an aquatic ecosystem. By determining the precise salinity that HAB cellular mortality is imminent, predictive models can be employed to predict the impacts of salt intrusion and groundwater management.

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