Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Natural Sciences

First Advisor

Harley, Heidi

Area of Concentration

Marine Mammal Science

Abstract

Harmful Algal Blooms (HABs) have increased in frequency, intensity and geographic distribution in the past several decades. Florida is an epicenter for an HAB, commonly referred to as red tide, caused by the algal dinoflagellate Karenia brevis, which produces the neurotoxin brevetoxin. Acute exposure to brevetoxin causes respiratory distress and has been associated with large scale marine mammal mortalities and fish kills. However, potential chronic effects of exposure, including via maternal transfer, have not been well characterized. Fetal and juvenile mammals may be particularly susceptible to the neurobiological effects of excitotoxins due to their developmental stage. Many resident coastal bottlenose dolphins in Sarasota Bay, Florida, have been exposed to brevetoxin across multiple blooms, and most dolphins survive these exposures. This dolphin community has been studied since 1970, providing a unique opportunity for assessing the long-term impacts of environmental exposures in a natural setting. Here we used population monitoring data compiled from 2003 through April 2025 to investigate the impacts of in-utero and first-year-of-life exposure to K. brevis blooms in Sarasota Bay dolphin calves. We sorted 109 calves born during 2004 through 2013 into four exposure groups based on gestation and birth dates, and historical bloom data: no exposure (n=42), exposed only during first year of life (n=10), exposed both in-utero and during first year of life (n=29), and exposed only in-utero (n=28). We evaluated the relationship between group membership and: (1) age at each calf’s separation from its mother, (2) whether the calf was seen after separation, an indicator of post-separation survival, and (3) survival curves. We found that calves likely exposed to red tide both in-utero and during their first year of life had twice the mortality risk at any given time during their lives compared to dolphins with no early-life exposure. Median age of calves at separation from their mothers as well as being seen post-separation varied nonsignificantly among exposure groups, although statistical tests indicated low power due to small sample sizes. These findings suggest that the effects of early life exposure to K. brevis blooms have negative cumulative impacts on bottlenose dolphin survival.

Rights

The author has granted New College of Florida the nonexclusive right to archive, make accessible, and distribute for educational purposes this work in whole or in part in all forms of media, now or hereafter known. The copyright of this work remains with the author.

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