Noel Y. Takeuchi1; Michael T. Walsh1; Martine deWit2; Robert K. Bonde3; Dean A. Bass4; David S. Barber1
The Florida manatee (Trichechus manatus latirostris) is an endangered herbivore with a population of approximately 3,800 remaining in the United States. Effective management and treatment of wild animals in rehabilitation requires an understanding of normal values, which includes information on current levels of environmental contaminants and normal levels of trace elements. Research in manatee health parameters and physiology has often been incomplete and narrow in scope. While many studies have examined trace metal concentrations in cetaceans and pinnipeds, only three studies have been reported for metal levels in manatees.1,2 Trace metals are essential for normal physiologic function, however, if found at abnormal levels, can cause adverse effects and may be detrimental to the health and development in individuals or populations. Anthropogenic contaminants, such as trace metals, have been investigated as a growing concern in many aquatic species, as these animals are exposed to a diverse group of toxicants and chemicals from their surrounding environment. Understanding the potential impact of trace metals in the aquatic environment requires that we develop an understanding of normal metal distribution and homeostasis in the Florida manatee, its environment, and the relationship to other aquatic species thriving in similar habitats, such as cetaceans and sea turtles. In addition, it is important for veterinarians and biologists to establish baseline levels in order to diagnose and treat a deficient or toxic animal. In collaboration with the United States Geological Survey's (USGS) Sirenia Project and the Florida Fish and Wildlife Conservation Commission (FWC), manatee health assessments were conducted in four locations throughout Florida: 1. Kings Bay, Crystal River 2. White Water Bay, Everglades 3. Lemon Bay, Englewood and 4. Indian River, Brevard County. We obtained data on whole blood and red blood cell samples from 60 free-ranging manatees and examined the samples for Ca, Mg, Cu, Zn, Mn, Li, Se, Sr, Mo, As, Ba, Cd, Co, Pb, Hg, Ni, Pt, Ag, Tl, and U. Of interest, zinc was quite elevated while selenium was quite low in whole blood compared to other aquatic species. Due to the dramatic differences in zinc levels, we are interested in how manatees maintain these levels without apparent or obvious adverse effects. Examination of the preliminary data revealed significant differences in trace metal concentrations based on location, suggesting an environmental contribution to trace metal load. In addition to free-ranging manatees, tissue samples from the Marine Mammal Pathobiology Laboratory were analyzed to determine distribution of metals, such as copper, zinc, selenium and arsenic. We are currently investigating the comparison of long-term captive manatee samples and archived blood samples to our current data to determine possible sources of elements in the various geographic locations and those on different diets. Whole blood trace element levels from wild cetaceans and sea turtles further illustrate common potential sources of trace metals and food relationships in species thriving in the Florida waters. In addition to providing information to improve veterinary care and husbandry, this study can also be used to further assist environmental agencies and management officials as they monitor trace metal levels in the changing aquatic environment.
Thank you to the United States Geological Survey, Florida Fish and Wildlife Conservation Commission, Doctors Data, Inc, and Sea World of Florida for their contribution and assistance with data collection. We also would like to thank the College of Veterinary Medicine at the University of Florida for financial support. This study is approved by the University of Florida Institutional Animal Care and Use Committee study 200801961 and U.S. Fish and Wildlife Conservation Commission permit MA791721-4.
1. O'Shea T.J., J.F. Moore, and H.I. Kochman. 1984. Contaminant concentrations in manatees in Florida. J Wildl Manage 48(3): 741-748.
2. Stavros H-C.W., R.K. Bonde, and P.A. Fair. 2008. Concentrations of trace elements in blood and skin of Florida manatees (Trichechus manatus latirostris). Mar Poll Bull 56(6): 1221-1225.