Elizabeth Hetherington

How Do Nitrogen Cycling Processes and Environmental Variability Affect Leatherback Sea Turtle Trophic Structure

and Reproduction?


FINAL SUMMARY Coming soon...


Proposed Project:

Introduction: The leatherback sea turtle (Dermochelys coriacea) is an endangered species split into several stocks. The declining eastern Pacific (EP) population is in critical danger of extinction2,3,

whereas the north Atlantic (NA) population is beginning to stabilize. Studies have speculated that

the differences in status between populations are due to a combination of anthropogenic and environmental impacts1,2,3,4. Anthropogenic impacts are well documented, but environmental

factors have been more difficult to directly link to population declines. Studies indicate that greater environmental variability in the Pacific may be preventing leatherbacks from acquiring essential

nutrients for reproduction1,5. I propose to apply two unique tools to determine whether

environmental variability is directly linked to leatherback declines via its impact on trophic structure.


My goal is to determine how environmental variability at the base of oceanographic food webs influences leatherback trophic ecology, reproductive output, and population dynamics using two novel techniques.

I. I will calculate temporal and spatial variation in phytoplankton cell size in the EP and NA to evaluate variability at the base of the food web. Phytoplankton cell size will provide information about nutrient availability and provide a tool to evaluate whether the environment and oceanography varies more in the EP compared with the NA.

II. I will use AA-CSIA to decipher the nitrogen dynamics at the base of the NA and EP food webs, as basal nitrogen variation can propagate up a food web, impacting higher trophic level species. AA-CSIA will also be used evaluate leatherback trophic position, which is crucial for their management. Additionally, I will evaluate baseline δ15N values using AA-CSIA in both regions over a time series which will provide crucial information on fluctuations at the food web base that propagate up to turtles and higher trophic position species. My collaboration with Dr. Jeffrey Seminoff at NOAA’s SWFSC insures my access to archived and future leatherback turtle samples from the NA and EP for these analyses.






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