Sea Turtles Trophic Ecology

Studying Trophic Ecology

Studying trophic ecology of the green turtle (Chelonia mydas) with the use of naturally occurring stable Carbon (d13C) and Nitrogen (d15N) isotopes. Green turtles are large, long-lived marine animals that play an important role in the shaping and regulation of coastal marine communities.  As large herbivores, green turtles impact seagrass and algae productivity and abundance and continue to represent an essential trophic pathway over expansive coastal marine habitats. The potential loss of ecological function due to depletion of these large, long-lived animals is poorly understood but may have serious implications for the maintenance of marine ecosystems.  We will use both field data and stable carbon and nitrogen isotope analyses to determine the tropic status of green turtles in disparate foraging habitats throughout the Eastern Pacific. 

 The use of naturally occurring stable isotopes is becoming a widely used technique to detect the foraging choices made by wildlife species.  This approach is based on the fact that stable isotope ratios in a consumer's body are related ultimately to those in its diet.  By measuring these ratios in animal tissue we are able to determine the types of foods consumed by that individual.  It is important to note that consumer vs. prey isotope ratios may not be identical; however, they are expected to correlate in some predictable and consistent manner.  This relationship is termed isotopic fractionation.  Further, due to varying rates of isotopic turnover in different tissue types, it has been shown that different tissues within animal bodies will reflect differing temporal diet histories.  Thus, it is possible to analyze various tissues separately to determine both short- and long-term dietary information.  Tissues with rapid isotopic turnover will reflect recent diet whereas tissues with slower turnover will reflect longer-term dietary averages.  Information from our aforementioned study on isotopic fractionation and turnover will aid our interpretation of spatial and temporal shifts in trophic status throughout different types of foraging areas.

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Using Stable Oxygen

Using stable oxygen, nitrogen, and carbon isotopes to establish foraging stock structure of green turtles (Chelonia mydas) in the Eastern Pacific. Genetic analysis has been useful for mixed nesting stock analysis at foraging areas.  However, little is known of the importance of different foraging areas for specific nesting rookeries.  Through developing and "isotopic map" the goal of this study is to determine the site-specific isotopic signatures of component green turtle foraging areas in the eastern Pacific.  These data will then allow us to determine the relative importance of different foraging areas for the major green turtle nesting beaches in the eastern Pacific.  

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Sea Turtle Population Structure

Sea turtle population structure and recovery in critical foraging habitats near the Baja California Peninsula.  (in collaboration with Antonio Resendiz S. Hidalgo   Universidad Auton—ma de Baja California; T. Todd Jones – University of British Columbia; Wallace J. Nichols – California Academy of Sciences).  As sea turtle recovery efforts continue in northwestern Mexico , understanding how populations are changing in habitats of varying quality are essential to identify population trajectories and determine the effectiveness of conservation efforts.  Present research efforts are a continuation of the long-term sea turtle research in the Gulf of California.  Top

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Trophic Ecology

Trophic ecology of juvenile loggerhead sea turtles (Caretta caretta) in the eastern Pacific Ocean: a study using stable Carbon (d13C) and Nitrogen (d15N) isotopes. (in collaboration with Hoyt Peckham, University of California at Santa Cruz)  Our knowledge of loggerhead foraging ecology in the eastern Pacific is limited.  This study will link isotopic values of tissues collected from loggerheads foraging off Baja California with their potential prey items. Ultimately, the goal of this study is to develop better understanding of spatial and temporal changes in loggerhead trophic status/foraging ecology.  By understanding what foods are most important to loggerheads in the Eastern Pacific and where these foods are found, we will be better able to mitigate loggerhead bycatch mortality.

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Sea Turtles and the Seri Indians

Sea turtles and the Seri Indians:  Bridging the gap between scientific research and indigenous knowledge with the Para-Ecologo program (in collaboration with Gary Nabhan, Center for Sustainable Ecosystems, Northern Arizona University).  The Para-Ecologo Program is a collaborative effort between scientists from the United States and Mexico and Seri Tribal members from northwestern Sonora, Mexico.  The mission of this year-round sea turtle program is to increase the awareness and participation of Seri Tribal members in Mexico's sea turtle conservation efforts.  The specific goals of this program are to

  1. determine current status of sea turtles in the Infiernillo Channel,
  2. identify human impacts on local sea turtle populations,
  3. promote Seri participation in the collection and analysis of scientific data, and
  4. increase communication of tribal members with biologists and conservation personnel in other parts of Mexico. 

Current efforts in the Infiernillo Channel region are both land based, with reconnaissance for discarded turtle remains and other evidence of illegal poaching, and water based, with monitoring efforts in the local marine ecosystem to determine population trends and local foraging ecology.  Click here for a summary of the project as described in a 1999 article in Marine Turtle Newsletter. 

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Last modified: 12/24/2014