The Florida manatee inhabits environments in which blooms of the toxic dinoflagellate, Karenia brevis, frequently occur. K. brevis produces brevetoxins, that result in fish kills, contamination of shellfish, and respiratory effects. Evidence suggests that the toxins produced by these blooms can impact immune function in marine organisms. This project will assess whether antioxidants can serve as a treatment protocol for manatees being treated for brevetoxicosis in rehab facilities.

Why We Care

From 2001 to 2016, 11 percent of manatee mortalities were attributed to exposure to brevetoxins from blooms of Karenia brevis. While deaths have been attributed to neurotoxicity, there is growing evidence from rescued manatees and other animal studies that oxidative stress also plays a role. Manatees and sea turtles exposed to red tide toxins consistently show signs of oxidative stress at the functional, cellular, and genetic levels.

The most recent evidence suggests a role for oxidative stress in brevetoxicosis through a specific inhibition of the enzyme thioredoxin reductase which is involved in alleviating the effects of oxidative stress. The ability to identify the impacts of toxins on individual organisms would be vital for the management of biotoxin risk and further protection of threatened and endangered species.

What Are We Doing

The project seeks to protect living marine resources, in particular threatened and endangered species. This will be accomplished through the development of a mechanism based intervention for brevetoxicosis. The evaluation of brevetoxin induced oxidative stress and potential interventions will first be assessed in a mammalian cell based model system. Those experiments inform studies with peripheral blood lymphocytes taken from both healthy and compromised manatees, which are more limited in availability. As the Florida manatee is still currently listed as endangered (status currently under review), in vitro approaches such as these described here are a requisite first step towards providing essential mechanistic and proof-of-concept data towards developing effective treatment options. Finally, this study will investigate the toxic effects of red tide toxin exposure on immune system in naturally-exposed wild Florida manatees during their rehabilitation in a captive setting and the potential for antioxidants to attenuate observed cellular effects, specifically oxidative stress that has been reported in rescued animals.

Results will include an assessment of whether antioxidant treatment has the potential to serve as a beneficial treatment protocol for manatees being treated for brevetoxicosis in rehab facilities. Our overall goal is to improve treatment options and enhance the success of returning animals to the wild.

Dr. Kathleen Rein of Florida International University leads this project. Co-leads are Drs. Yuan Liu (Florida International University) and Catherine Walsh (Mote Marine Laboratory). The project is funded through the NCCOS Ecology and Oceanography of Harmful Algal Bloom (ECOHAB) Program.