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Dissertation
Mechanistic modeling of the effects of climate change on sea turtle migration to nesting beaches
Doctor of Philosophy (Ph.D.), Drexel University
01 Dec 2014
DOI:
https://doi.org/10.17918/etd-6096
Abstract
The purpose of this dissertation was to study how sea turtles currently respond to changes in temperature, in order to predict how they may respond to climate change in the future. I looked at two of the most commonly reported responses to changes in temperature: phenology shifts and changes in the duration of remigration intervals. I studied how the timing of leatherback nesting at three nesting beaches responds to temperature changes at both the nesting and the foraging grounds. There was no effect for local temperatures, but there was an overall trend for delayed nesting with increased temperatures at the foraging grounds. Deviations from this trend as well as different trends found in other studies suggest that the phenological response is complex and variable. To look at remigration intervals, I developed a theoretical, physiologically-based model that links temperature to resource availability and its accumulation by sea turtles, remigration intervals, and nesting numbers. The model shows that apparent nesting cohorts are formed not by life history traits but rather by a population-level response to environmental temperatures and that these cohorts are unstable over time. Using the model to explore different temperature history scenarios showed that short pulses of altered temperatures can have a large effect on nesting numbers. Cold pulses tend to synchronize nesting in the following year, owing to decreased remigration intervals, while warm pulses tend to delay nesting in a less synchronized way. Cyclical temperature variation increases remigration intervals in general and leads to a cyclical response in both remigration intervals and nesting numbers, with a lag and amplitude that vary with cycle duration. Adapting this model to specific populations of leatherback turtles reveals that it is able to capture both year-to-year and decade-to-decade trends in remigration intervals for both populations. Due to the difficulties in isolating the effect of strong population trends on nesting numbers and oscillations, it is unable to predict nesting numbers. Future model iterations should include inherent population trends to allow for better comparison and forecasting as well as using the model to help plan conservation efforts and properly interpret changes in nesting numbers.
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Details
- Title
- Mechanistic modeling of the effects of climate change on sea turtle migration to nesting beaches
- Creators
- Noga Neeman - DU
- Contributors
- Michael P. O'Connor (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Biology; College of Arts and Sciences; Drexel University
- Other Identifier
- 6096; 991014632677504721