The Effects of Cold-Stress Syndrome and Harmful Algal Blooms Leading to Stress in the Species Trichechus manatus latirostris

Defense Date


Document Type


Degree Name

M.S. Marine Biology

First Advisor

Curtis Burney

Second Advisor

Caryn Self-Sullivan


Florida manatees (Sirenia: Trichechidae: Trichechus manatus latirostris) are endangered marine mammals with a population size estimated to decline over the next forty years (Deutsch et al. 2008). Manatees appear to have a resilient immune system (Bossart et al. 2003) however anthropogenic factors, cold weather, and/or exposure to harmful algal blooms (HABs) negatively affect the health of manatees (Walsh et al. 2005). Environmental and anthropogenic stressors affect immunocompetence (Romano et al. 2002) leaving the manatee susceptible to cold-stress syndrome (CSS), brevetoxicosis and secondary infections (Halvorsen and Keith 2008).

There is little experimentation on the leading causes of manatee stress resulting in immune dysfunction due to research limitations, due to federal protection as an endangered species. The purpose of this capstone is to examine the results of prolonged exposure to cold water and HABs leading to stress, a significant factor in manatee immunosuppression via literature review. There is a strong possibility that simultaneous stressors, such as the combination of cold-stress and HABs, may affect immune competence and increase a manatees susceptibility to environmental stressors and diseases (Walsh et al. 2005).

CSS is a combination of several different disease processes triggered by sup-optimal temperatures (M. de Witt, Personal Communication). Prolonged exposure to cold water temperatures, 20 degrees Celsius or below, can lead to CSS and weaken the manatees' immune system (Bossart et al. 2003, Walsh et al. 2005). Red tide or HABs are events characterized by the proliferation of a specific toxic alga (Anderson 1995). Toxic HABs produce neurtoxins, hemolytic agents, and biotoxins (Fleming et al. 2003). Karenia brevis (K. brevis) is one of many dinoflagellates responsible for red tide and causes brevetoxicosis in manatees. The most common route of brevetoxin exposure in manatees is through inhalation (Bossart 2001) resulting in chronic immunologic compromise (Bossart et al. 1998).

A manatee with these conditions often suffer from immunosuppression, (Bossart et al. 1998, 2003) a result of increased glucocorticoid concentrations that persist for extended periods of time in response to chronic stress (Tripp et al. 2001, Cooke et al. 2004, Reeder and Kramer 2005, Turner et al. 2002). Glucocorticoids and adrenocorticotropic hormones (ACTH) are associated with stress responses; cortisol is the predominant immunoreactive manatee glucocorticoid used to measure chronic stress (Tripp et al. 2011). Manatees that endure environmental stressors have weak immune systems (Romano et al. 2002) leaving them susceptible to secondary infections, such as the papillomavirus (PV) and biofouling organisms (Halvorsen and Keith 2008).

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