Date of Award


Document Type


Degree Name

Master of Science (MS)


Ocean Engineering and Marine Sciences

First Advisor

Kevin B. Johnson

Second Advisor

Austin Fox

Third Advisor

Glenn Miller

Fourth Advisor

Richard B. Aronson


The Indian River Lagoon (IRL) estuary has experienced eutrophication and degraded water quality due to high nutrient input, urbanization, and anthropogenic stressors. High nutrient input and restricted estuarine hydrology promotes algal blooms. Algal blooms or harmful algal blooms (HABs) are a global concern as they can cause negative ecological and economic impacts. The frequency and range of HABs is expected to be exacerbated by climate change and altered oceanic and estuarine conditions. Research on the formation and frequency of HABs is an ongoing global effort, but algal blooms are often dynamic and patchy making them difficult to study. This study sought to expand databases of phytoplankton distribution and environmental drivers in the IRL and coastal Atlantic Ocean. Between the IRL and coastal Atlantic Ocean, salinity was the most influential environmental variable shaping community compositions and biodiversity. However, nutrient data was limited and did not offer compelling evidence of strong influence on phytoplankton distribution, but some associations were determined. Overlap in estuarine and coastal community composition is proposed to be a result of irregular and intermittent coastal and estuarine mixing associated with the Port Canaveral Locks System, as well as mixing associated with Sebastian Inlet. However, communities within the central BRL were distinct from coastal communities at the same latitude suggesting minimal phytoplankton transport from the coast to the IRL in the central BRL. The taxa driving these similarities in estuarine and coastal communities are likely ubiquitous euryhaline diatoms and some dinoflagellates that dominate in the IRL and coastal ocean. Phytoplankton biodiversity, species richness, and species evenness were also determined to be higher in the coastal ocean and is attributed to osmotic stress along a gradient of decreasing salinities from 10-30 PSU, as found in other estuaries. Diatom abundance in the IRL was significantly higher than the coastal ocean, but dinoflagellates and other plankton were not statistically different between IRL and coastal sites. Cyanobacteria were generally present at low abundances (<2x104 cells mL-1) except for a unique cyanobacteria bloom referred to as the CyanoHAB of 2020 in the IRL and BRL in 2020. The bloom reached densities of over 5x106 cells mL-1 and persisted from July-August to December. Potential bloom drivers were determined to be temperature, nitrate, and phosphate, but limited nutrient data may limit the accuracy of these findings.

Available for download on Tuesday, July 30, 2024

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