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First published online July 17, 2009
Journal of Experimental Biology 212, 2349-2355 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.027565

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Carbon and nitrogen stable isotope turnover rates and diet–tissue discrimination in Florida manatees (Trichechus manatus latirostris)

Christy D. Alves-Stanley¹ and Graham A. J. Worthy^1,2,*

¹ Physiological Ecology and Bioenergetics Lab, Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816, USA
² Hubbs-SeaWorld Research Institute, 6295 Sea Harbor Drive, Orlando, FL 32821, USA

^* Author for correspondence (e-mail: gworthy{at}mail.ucf.edu)

Accepted 3 May 2009

The Florida manatee (Trichechus manatus latirostris) is a herbivorous marine mammal that occupies freshwater, estuarine and marine habitats. Despite being considered endangered, relatively little is known about its feeding ecology. The present study expands on previous work on manatee feeding ecology by providing critical baseline parameters for accurate isotopic data interpretation. Stable carbon and nitrogen isotope ratios were examined over a period of more than 1 year in the epidermis of rescued Florida manatees that were transitioning from a diet of aquatic forage to terrestrial forage (lettuce). The mean half-life for ¹³C turnover was 53 and 59 days for skin from manatees rescued from coastal and riverine regions, respectively. The mean half-life for ¹⁵N turnover was 27 and 58 days, respectively. Because of these slow turnover rates, carbon and nitrogen stable isotope analysis in manatee epidermis is useful in summarizing average dietary intake over a long period of time rather than assessing recent diet. In addition to turnover rate, a diet–tissue discrimination value of 2.8 for ¹³C was calculated for long-term captive manatees on a lettuce diet. Determining both turnover rate and diet–tissue discrimination is essential in order to accurately interpret stable isotope data.

Key words: turnover, stable isotope, Florida manatee, diet–tissue discrimination, ¹³C, ¹⁵N, Trichechus manatus, feeding ecology

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