RESEARCH

Overview

I investigate questions at the intersection of animal behavior, population biology, community ecology, and global change to build understanding of the causes and consequences of life history variation in marine species. To this end, I ask three main questions:

  1. How does resource use (diet & habitat) shape life history traits (e.g., growth)? 

  2. How do natural and human stressors influence trophic interactions and life history traits?

  3. What are the cumulative effects of multiple stressors on population and community dynamics? 

I have examined these questions throught the U.S. Gulf of Mexico and Atlantic, primarily in sea turtles and other marine vertebrates. 

 

My research relies on the integration of two primary tools: (1) sclerochronology, the study of concentric growth layers in calcified animal tissues (e.g., turtle bone, marine mammal teeth), and (2) ecogeochemistry, the use of stable isotopes and trace elements to infer past diet and habitat use of consumers. Together these techniques can provide invaluable insight into the ecology of otherwise difficult to study species and life stages. I often apply these techniques to the study of threatened and endangered species to inform conservation and management efforts. 

 

A final aim of my research is to maximize the use of dead stranded marine organisms—both modern and historical—in ecological research. Information gleaned from their tissues can enable us to investigate previously intractable questions in marine ecology. 

Below you will find information on my current research projects. To learn about my past research, click here.

Image by NOAA

Marine Top Predator Trophic Dynamics

Despite decades of food web research, we still have a poor understanding of how environmental change alters marine top predator trophic interactions through time. For my NSF Postdoctoral Fellowship, and in collaboration with Drs. Kelton McMahon (URI), Larisa Avens (NOAA), and Michael McGowen (Smithsonian NMNH), I am using a retrospective approach to investigate how marine mammals, fish, and sea turtles have adjusted their foraging strategies in response to shifts in climate and prey, predator, and competitor abundance over the past century. To this endI am sampling specimens from historical collections (e.g., Smithsonian, NOAA) for nitrogen isotopes of amino acids to examine how common bottlenose dolphin, short-beaked common dolphin, loggerhead sea turtle, Kemp's Ridley sea turtle, and Atlantic of trophic position and niche breath have changed over time. Together, these data will provide a mechanistic understanding of the trophic response of key marine top predators to recent environmental change. Such information is paramount to predicting the consequences of future ecosystem change, and these topics were highlighted as high priority research areas in the recent decadal review of ocean science by the National Academy of Sciences.

Life History Variation & Population Dynamics

Despite having population-level distributions spanning whole continental shelves or ocean basins, individual sea turtles often display remarkable inter-annual fidelity to specific foraging grounds, resources, and migratory routes. Such life history variation has been linked to differences in a suite of demographic rates in multiple sea turtles species and thereby holds the potential to fundamentally alter a species population dynamics. However, this information has yet to be robustly integrated into demographic models, largely due to insufficient data. I am actively working in collaboration with Dr. Selina Heppell to develop spatially-explicit, age-structured matrix population models for the critically endangered Kemp's ridley sea turtle, a species whose population is divided into distinct subgroups (Atlantic vs. Gulf of Mexico) that have unique demographic rates (growth, maturation schedules) and oceanic stage duration. With these models we are evaluating the relative contribution of Atlantic Kemp's Ridleys to overall species population growth.

DpFncH6XUAI2rt_-2.jpg
Image by Nariman Mesharrafa

Multiple Stressors & Coral Reef Foodweb Dynamics

Coral reefs are the world's most biodiverse, productive, and economically valuable marine ecosystems, making their conservation uniquely important to meeting UN Sustainable Development Goals. However, coral reefs are under immense pressure globally due to synergistic effects of climate change and suites of anthropogenic stressors. Few studies have examined the impacts of multiple stressors on coral reefs. As such, little is known about their cumulative effects on the resilience of these iconic systems, including how they reorganize, or ‘rewire,’ coral reef food webs. Beginning in 2022 as a Hess Postdoctoral Research Fellow at the University of Victoria, I will use CSIA-AA to evaluate the interactive effects of gradients in human disturbance and marine heatwaves on coral reef food web dynamics on Kiritimati atoll, from shifts in baseline energy sources, to strength and number of trophic interactions, to food web complexity and length. This work will shed new light on the mechanisms supporting coral reef stability and resilience, information critical to predicting how climate change will alter ecosystem structure and reef fishery productivity and ultimately countering the global decline of these critically important ecosystems.

Endangered Species Ecology

A cornerstone of my research program is the study of threatened, endangered, and protected species to build fundamental ecological knowledge that can be used to better conserve and manage their populations. My current research is focused on two critically endangered species in the Gulf of Mexico (GoM): hawksbill sea turtle and Rice's whale. Hawksbills inhabitant US waters (the northern extent of their range) but we have little understanding of their ecology in these habitats. Recent collaborative work with NOAA scientists has revealed a pronounced dichotomy in hawksbill growth rates between the western and eastern GoM, which may be linked to differences in diet. Ongoing work is integrating CSIA-AA and gut content analyses of stranded turtles to evaluate trophic plasticity as a potential driver of growth variability, and assess potential effects on population dynamics. I have also recently initiated collaborative research with an interdisciplinary team of scientists from Stanford University, George Mason University, Mt. Sinai Medical School, and the Smithsonian NMNH to study the ecology of the newly described Rice's whale (previously GoM Bryde's whale). Our work integrating bulk SIA, CSIA-AA, hormone analyses, and emergent contaminant analyses will provide critical insights needed to conserve the world’s most enigmatic and endangered whale species.

image.jpeg