Regional Studies in Marine Science 48 (2021) 102011
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Contents lists available at ScienceDirect
Regional Studies inMarine Science
journal homepage: www.elsevier.com/locate/rsma
Stable isotopes used to infer trophic position of green turtles (Chelonia
ydas) fromDry Tortugas National Park, Gulf ofMexico, United States
avid C. Roche a,∗, Michael S. Cherkiss a, Brian J. Smith b, Derek A. Burkholder c,
risten M. Hart a
Wetland and Aquatic Research Center, U.S. Geological Survey, Davie, FL 33314, USA
Department of Wildland Resources and Ecology Center, Utah State University, Logan, UT 84322, USA
Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, Dania Beach, FL 33004, USA
a r t i c l e
i n f o
Article history:
Received 28 May 2021
Received in revised form 20 August 2021
Accepted 15 September 2021
Available online 20 September 2021
Keywords:
Sea turtle
Carbon
Nitrogen
Stable isotopes
LMM
a b s t r a c t
Evaluating resource use patterns for imperiled species is critical for understanding what supports their
populations. Here we established stable isotope (δ13C, δ15N) values for the endangered green sea turtle
(Chelonia mydas) population found within the boundaries of Dry Tortugas National Park (DRTO), south
Florida, USA. There is little gene flow between turtles sampled at DRTO and in other rookeries in
Florida, underscoring the need to study this distinct population. Between 2008 and 2015 we collected
multiple sample types (skin [homogenized epidermis/dermis], whole blood, red blood cells, plasma,
carapace) from 151 unique green turtles, including 43 nesting females and 108 in-water captures; some
individuals were resampled multiple times across years to evaluate consistency of isotope signatures.
Isotopic ratios ranged from -27.3 to -5.4 for δ13C and 3.7 to 10.6 for δ15N. Using linear mixed models,
we evaluated covariates (sample type, turtle size and year) that best explained the isotope patterns
observed in turtle tissues. Predictions from the top model