Graduation Year

2025

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Margaret Mars Brisbin, Ph.D.

Committee Member

Mya Breitbart, Ph.D.

Committee Member

Sugandha Shankar, Ph.D.

Keywords

Bacteria, Cobalamin, Metabarcode, Micronutrients, Old Tampa Bay

Abstract

Harmful Algal Blooms (HAB) negatively affect economies, ecosystems, and public health through mass proliferation and toxin production. The HAB species, Pyrodinium bahamense var. bahamense, is a saxitoxin-producing dinoflagellate found in tropical and subtropical estuarine waters globally. In two Florida estuaries, Old Tampa Bay and the Indian River Lagoon, P. bahamense is a recurrent HAB species, and the exact timing and intensity of bloom peaks in these estuaries vary interannually. Factors that are suspected to contribute to blooms include temperature, residence times, nutrients, and salinity. However, many HAB dinoflagellates require vitamin B12 for growth and bloom development. Thus, B12 may influence P. bahamense blooms in Old Tampa Bay and the Indian River Lagoon, and interact with bacteria that deliver this micronutrient. Neither the role of B-vitamins nor the role of bacterial interactions in supporting P. bahamense blooms in Florida estuaries has been directly investigated. Using Chlorophyll a fluorescence as a proxy for growth, our results demonstrate that P. bahamense is auxotrophic for B12 and cannot grow without it. Bacteria recruited from Old Tampa Bay sea surface water before reaching bloom levels were unable to support growth when B12 was withheld. However, bacteria recruited from the Indian River Lagoon during a bloom may be able to supplement B12 to sustain growth. Our findings suggest B12 is essential for fueling P. bahamense blooms, and distinct bacterial communities are essential for bloom development.

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