Meet the Scientist: Erin Dillon

Name: Erin Dillon

Position/Degree program: PhD candidate

University: University of California, Santa Barbara

Correct pronouns: she/her

Website: https://erinmdillon.wordpress.com/

Twitter: @erinmdillon

Research interests: conservation paleobiology, historical ecology, coral reefs, community ecology

1. What is your favorite part about being a scientist and how did you come to work in this field?

My favorite parts about being a scientist are the independence to follow my curiosity and wander into the unknown in search of an answer, the flexibility to manage my own work schedule and research priorities, and the rush of excitement that comes from looking at new data. The diverse array of tasks associated with my work – from collecting and processing samples, analyzing data, and writing proposals and manuscripts to giving presentations and discussing ideas with collaborators – means that each day is different and exciting. 

Fig 1. Collecting a sediment core from the Las Perlas Archipelago along the Pacific coast of Panama. (Photo credit: Sean Mattson

I first became interested in coral reef ecology as an undergraduate student at Stanford University, although my passion for marine biology began when I was in middle school. The summer after my first year in college, I had the chance to assist with a research project on Palmyra Atoll, a remote island located in the central Pacific Ocean about 1000 miles southwest of Hawaii. I was blown away by the reefs and the overwhelming abundance and complexity of life that inhabited them. Never before had I been in the company of a reef so full of predators! But this was not true for every reef that I visited as part of my undergraduate program, and I became curious about these spatial differences, what was natural for a reef in any given location, and how this variation could help guide conservation efforts.

I still remember my first introduction to historical ecology, which was a seminar I attended at Hopkins Marine Station in Monterey, California. Dr. Loren McClenachan was discussing her work using historical photographs from the Florida Keys to document the loss of large trophy fish since the 1950s. That was an aha moment for me, when I realized that I could combine my interests in ecology, history, and conservation.   

After graduating from college, I applied for an opportunity to work at the Smithsonian Tropical Research Institute in Panama on a coral reef paleoecology project with Dr. Aaron O’Dea. What was originally intended to be a three-month-long internship became a two-year-long visit and eventually a PhD project – and the rest was history! 

2. What are your main research questions? How would you explain this to someone who didn’t have working knowledge of your discipline?

How abundant were sharks on coral reefs before humans? Sharks play important roles as predators, cultural symbols, and ecotourism attractions, yet they are susceptible to overfishing. Many coastal shark populations have undergone dramatic declines over the last several decades, and at least a quarter of shark species and their relatives are threatened with extinction. However, the timing and extent of shark declines are poorly understood. In order to effectively recover shark populations and their ecological functions, it is useful to first document what was lost. My research aims to reconstruct reef shark communities over the last several thousand years using dermal denticles (shark scales), which are shed by sharks and accumulate in marine sediments. I use these microscopic “skin teeth” as a time machine to characterize shark communities before major human impact and quantify how they have changed over long ecological timescales. In turn, these data can be applied to inform shark management and ecology.

3. How does your research/goals/outreach contribute to the understanding of climate change, evolution, paleontology, or to the betterment of society in general? 

In the face of ongoing fisheries exploitation, the ecological status and roles of sharks on coral reefs as well as the timing and magnitude of decline remain uncertain. Long-term shark survey data are limited, hindering efforts to set appropriate management targets and determine how shark removals have affected reef ecosystems. My research helps fill this gap by providing a historical perspective on the patterns, drivers, and consequences of change in reef shark communities. These paleoecological data can complement modern ecological studies to 1) contextualize recent change in shark communities, 2) define natural ranges of variability, 3) explore what governs shark abundances and the ecological roles they play on intact reefs, and 4) assess how human activities altered reef ecosystems through the depletion of predators. By going back in time and investigating what predator communities were like on reefs of the past in different regions, we can better understand how their impacts on reef ecology have shifted over time as well as use these pre-exploitation reference points to guide the management of their populations in the future.

4. If you are writing about your research: What are your data and how do you obtain your data? In other words, is there a certain proxy you work with, a specific fossil group, preexisting datasets, etc.?

The recent fossil record on coral reefs contains a treasure trove of skeletal material – the ghost of reefs past – that can tell us what these ecosystems looked like before contemporary survey data or even before humans. In particular, I work with shark dermal denticles. Dermal denticles are the microscopic, tooth-like scales that cover the bodies of sharks and rays. These “skin teeth” – which are smaller than a sesame seed – are shed by sharks and accumulate in marine sediments, where they can preserve a time-averaged record of shark occurrences. Collaborators and I have been developing an approach to recover denticles from coral reef sediments, test their ecological fidelity, and interpret this record. For example, we first built a reference collection of denticles isolated from museum specimens and characterized variation in denticle morphology across shark taxa with different life modes. We then explored the relationship between the denticle record and conventional shark surveys to help ground truth the method. Our work so far has shown that denticle assemblages retain ecological information about past shark abundances and community composition. We’ve now been collecting bulk sediment samples from modern and mid-Holocene reefs as well as multiple-meter-long sediment cores to recover denticles from reefs of different ages in the Caribbean and Pacific.

Fig 2. Scanning electron microscope images of representative denticles from three shark families commonly found on coral reefs. (Photo credit: Erin Dillon & Jorge Ceballos)

5. What advice do you have for aspiring scientists?

I have three pieces of advice for aspiring scientists:

  1. Seek out mentors. Identify and connect with mentors who can offer advice, introduce you to other people in the field, and advocate for you as you grow and pursue new opportunities.
  2. Communication is a two-way street. Hone your written and verbal communication skills and have confidence in yourself and your ideas. At the same time, listen and learn from others, be open to having your viewpoints challenged, and don’t be afraid to ask questions.

Don’t give up. Pursuing a career in science is challenging and, at times, isolating. Build a solid support system, learn from (but don’t dwell on) rejections, celebrate your accomplishments – both big and small, find balance between your work and other aspects of your life, and, importantly, stay true to your passions.

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