Stable Isotope Laboratory
You are what you eat!
The Stable Isotope Laboratory facility at the Southwest Fisheries Science Center is an interdisciplinary stable isotope sample processing facility directed by Dr. Jeffrey Seminoff and managed by Garrett Lemons. The lab hosts a diverse network of researchers, collaborators, and students from the Center and other Institutions to conduct stable isotope research about the ecology of endangered species and other marine taxa (seabirds, fish, invertebrates, zooplankton, and marine mammals). In-house research investigates marine mammal and sea turtle ecology and management. Ongoing projects include life stage-based habitat use, feeding ecology (dietary analysis and trophic structure) in relation to life-history traits, as well as analysis of animal migration and marine isoscape mapping.
Lab capabilities include lipid extraction from biological samples via accelerated solvent extraction (ASE system), Soxhlet and sonication extraction, bone cutting with low-speed Isomet saw, bone polishing, micro-sample milling of bone, tooth, scute, and otolith samples, precision sample weighing, lyophilization (freeze-drying), and heat drying of organic and inorganic samples. Stable isotopic analyses include carbon, nitrogen, sulfur, and hydrogen. The Lab contracts mass spectrometry analysis externally to Washington State University, University of Florida, University of New Mexico, University of California, and University of Hawaii at Manoa.
Stable Isotope Analysis
In nature, atoms that occur in non-radioactive variations are called stable isotopes. These isotopes are of the same element but vary in the number of neutrons they contain. The heavier variation, or isotope with more neutrons, is less abundant than the lighter isotope. For example, the lighter 12C is found in nature in much greater abundance than the heavier 13C. Marine animals like sea turtles assimilate these isotopes from their diets and environment into their tissues. This “you are what you eat” paradigm allows researchers to use stable isotope analysis to understand trophic ecology, behavior, and movement of marine organisms. Because of these predictable patterns of isotope ratio variation in nature, isotope analysis of specific elements are especially informative, and while carbon and nitrogen are generally the most useful in marine ecology, other elements such as sulfur, hydrogen, and even oxygen can also be informative.
Most sample preparation done by Marine Turtle Ecology & Assessment Program researchers for stable isotope analysis follows a standardized step-wise process of rinsing, freezing, lyophilization, lipid extraction, homogenization, and weighing. Sample preparation is a critical step for the analyses and ensures high-quality, reliable data from each sample
Select Publications
- Jones TT, Seminoff JA (2013) Feeding Biology: Advances from Field-Based Observations, Physiological Studies, and Molecular Techniques. In: Musick, J., J. Wyneken, and K. Lohman (Eds.), Biology of the Sea Turtles, Volume 3. CRC Press, Boca Raton, FL., pp 211-248.
- Lemons, G., T. Eguchi, B.N. Lyon, R. LeRoux, and J.A. Seminoff. 2012. Effects of blood anticoagulants on stable isotope values of sea turtle blood tissue. Aquatic Biology 14:201-206.
- Lemons, G., R. Lewison, L. Komoroske, A. Gaos, C.-T. Lai, T. Eguchi, P. Dutton, R. LeRoux, and J.A. Seminoff. 2011. Trophic ecology of green sea turtles in a highly urbanized bay: insights from stable isotopes and mixing models. Journal of Experimental Marine Biology and Ecology 405:25-32
- Seminoff JA, Jones TT, Hastings M, Eguchi T, Jones D (2009) Stable carbon and nitrogen isotope discrimination in soft tissues of the leatherback turtle (Dermochelys coriacea): insights for trophic studies of marine turtles. Journal of Experimental Marine Biology and Ecology 381:33-41.
- Seminoff JA, Jones TT, Eguchi T, Dutton PH (2006) Stable isotope discrimination (δ13C and δ15N) between soft tissues of green sea turtles Chelonia mydas and their diet. Marine Ecology Progress Series 308: 271-278.
- Seminoff JA, Bjorndal KA, Bolten AB (2007) Stable carbon and nitrogen isotope discrimination and turnover in Pond Sliders Trachemys scripta: insights for trophic study of freshwater turtles. Copeia 2007(3):534-542
- Seminoff JA, Benson SR, Arthur KE, Eguchi T, Dutton PH, Tapilatu R, Popp BN (2012) Stable isotope tracking of endangered sea turtles: validation with satellite telemetry and δ15N analysis of amino acids. PLoS ONE. 7(5): e37403. doi:10.1371/journal.pone.0037403
- Turner Tomaszewicz, C, Seminoff JA, Peckham H, Avens L, Goshe L, Rguez-Baron JM, Kurle CM (2018) Expanding the coastal forager paradigm: Long-term pelagic habitat use by green turtles (Chelonia mydas) in the eastern Pacific Ocean. Marine Ecology Progress Series. doi.org/10.3354/meps12372
- Turner Tomaszewicz C, Seminoff JA, Kurle CM (2017) Stable isotope discrimination factors and between-tissue isotope comparisons for bone and skin from captive and wild green sea turtles (Chelonia mydas). Rapid Communications in Mass Spectrometry. https://doi.org/10.1002/rcm.7974
- Turner Tomaszewicz C, Seminoff JA, Peckham SH, Avens L, Kurle CM (2017) Intrapopulation variability in the timing of ontogenetic habitat shifts in sea turtles revealed using δ15N values from bone growth rings. Journal of Animal Ecology, doi:10.1111/1365-2656.12618.
- Turner Tomaszewicz C, Seminoff JA, Avens L, Kurle CM (2016) Methods for sampling sequential annual bone growth layers for stable isotope analysis. Methods in Ecology and Evolution 7:556-564.
- Turner Tomaszewicz C, Seminoff JA, Ramirez M, Kurle CM (2015) Effects of demineralization on the stable isotope analysis of bone samples. Rapid Communications in Mass Spectrometry 29:1879-1888.
- Turner Tomaszewicz C, Seminoff JA, Peckham SH, Avens L, Goshe L, Bickerman K, Rodriguez-Baron JM, Kurle CM (2015) Age and residency duration of loggerhead turtles at a North Pacific bycatch hotspot using skeletochronology. Biological Conservation 186:134-142.
Image of microbalance used to weigh samples for stable isotope analysis. Photo: NOAA Fisheries
