Marine Biology

, Volume 150, Issue 6, pp 1083–1092 | Cite as

Simulated green turtle grazing affects nutrient composition of the seagrass Thalassia testudinum

  • Kathleen L. Moran
  • Karen A. BjorndalEmail author
Research Article


Before populations of green turtles (Chelonia mydas) were severely reduced by human overexploitation, the seagrass Thalassia testudinum was intensively grazed by green turtles in the Caribbean. To explore how nutrient composition of T. testudinum pastures responds to intense grazing pressure, we simulated green turtle grazing in 15 plots (each 3 m × 3 m) for 16 months in the central Bahamas. Comparisons of clipped plots with 15 adjacent control (unclipped) plots revealed that simulated grazing resulted in significantly higher energy, nitrogen, phosphorus, lignin, cutin, and condensed tannin content in blades in clipped plots, but sediment organic content was not affected. By continually re-cropping blades in grazing plots, turtles ingest young, actively growing blade tissue with higher energy, nitrogen, and phosphorus concentrations. Our 16-month clipping trial did not generate the expected decline in nutrient content in T. testudinum blades under intensive grazing. However, significant decreases in nitrogen and organic matter reserves in rhizomes, with declines apparent after 16 and 11 months, respectively, indicate that nutrient content of blades and/or blade productivity may decline under continued clipping.


Lignin Nutrient Composition Condensed Tannin Green Turtle Cell Wall Constituent 
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We are grateful to A. Bolten, whose insights and discussions improved the quality of the study and whose assistance with logistics made this study possible. C. Chapman, L. Chapman, T. Frazer, and J. Ogden provided valuable advice. We thank T. Arnold for analyses of secondary compounds. P. Eliazar, R. Fethiere, J. Funk, L. Schwandes, L. Sollenberger, and the UF Forage Evaluation Support Laboratory assisted with lab analyses. R. Co, L. Conway-Cranos, C. Davis, J. Greenawalt, J. Hale, R. Kuo, P. Lamarque, B. Reardon, S. Schopmeyer, C. Ward-Paige, D. Winchester, and D. Wood were invaluable in data collection. This paper benefited from the participation of KAB in the Long-Term Ecological Records of Marine Communities Working Group supported by the National Center for Ecological Analysis and Synthesis (funded by U.S. National Science Foundation grant DEB-0072909, the University of California, and the University of California, Santa Barbara). The staff of the Caribbean Marine Research Center supplied logistical support and access to the field site. Financial support was provided by N. Thompson and the National Marine Fisheries Service, Southeast Fisheries Science Center; J. Marr, N. Langley, and the Caribbean Marine Research Center; Disney Wildlife Conservation Fund; National Fish and Wildlife Foundation; the PADI Foundation; Sigma Xi; and the American Museum of Natural History.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  1. 1.Archie Carr Center for Sea Turtle Research and Department of ZoologyUniversity of FloridaGainesvilleUSA

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