Feature Friday: Hannah Rempel

Hi, Hannah Rempel! Welcome to Reefbites. 

@queenparrotfish (Twitter)

https://www.marineconservationlab.org/parrotfish.html (Lab research page)

Hannah is a M.S. student, Biological Sciences at California Polytechnic State University, San Luis Obispo. Her research focuses on ecological drivers and impacts of parrotfish predation across the Greater Caribbean. Read more about her work below! 

Give an elevator pitch of what your research/project is about.

Parrotfishes are ecologically important herbivores that indirectly benefit corals by grazing algae.
However, some species also occasionally graze coral – which has direct negative impacts on
targeted coral colonies. My research addresses the patterns and impacts of parrotfish predation
on coral communities. Specifically, I am studying the patterns of coral tissue regeneration from
parrotfish bite scars for one of the most intensively grazed Caribbean coral species, Orbicella
annularis. In addition, I am studying how the community composition of reefs throughout the
Greater Caribbean influences the relative intensity of parrotfish predation across coral species.
If you are interested in learning more about this research, please see a recent publication on our
work here: https://rdcu.be/b5Vgl (for those without institutional access to Coral Reefs, note that
this is a full-text view-only link).

Why is this research/project important and timely?

Parrotfish coral predation (corallivory) can cause mortality of juvenile corals and partial
mortality of mature colonies. Research also suggests that corallivory may impact coral growth,
reproduction, and disease susceptibility. However, the ecological factors that influence the
relative intensity of corallivory and the capacity of corals to heal from parrotfish bite scars
remain poorly understood. I hope that by helping to fill these knowledge gaps, we can better
understand the net impact of parrotfishes as both herbivores and corallivores.

What is the broader impact and implication of your findings? 

Numerous studies have shown that the Great boulder star coral (Orbicella annularis) is one of
the most intensely grazed Caribbean coral species by parrotfishes. Some researchers have
expressed concern over the impacts of parrotfish predation because O. annularis is an
ecologically important framework building coral and IUCN Red List endangered species. Our
research suggests that O. annularis can fully regenerate tissue after parrotfish predation up to a
certain size-based threshold. The vast majority of the parrotfish bite scars we observed at a point
in time were below this threshold size – indicating that the majority of scars are likely to result in
minimal tissue loss. However, while large bite scars were infrequent, our work suggests they
have minimal healing. Therefore, it is important to understand what factors influence parrotfish
bite scar size and abundance.


Our ongoing research seeks to address how parrotfish and coral community composition
influence the size and abundance of scars across coral species throughout the Greater Caribbean.
Our findings indicate that for the majority of coral species, parrotfish have very low instances of
predation, and the relative intensity of predation is largely independent of parrotfish biomass.
Some researchers have questioned whether marine reserves that increase the biomass of
parrotfishes may increase the intensity of corallivory. Despite comparing patterns across multiple areas of the Caribbean spanning broad gradients in coral cover and parrotfish biomass, we did
not find any evidence for this.

How did you come to work in this field/project?

Ironically, it was while conducting an internship studying primate behavioral ecology in Puerto Rico as an undergraduate that I began learning to SCUBA dive on weekends and became fascinated with coral reef ecology. Later, I studied abroad on Bonaire in the Dutch Caribbean and returned to conduct independent research on parrotfish behavioral ecology my senior year. After graduating, I worked as an Assistant Biologist for the STINAPA Bonaire National Parks Foundation. While I loved working on the management side of coral reef ecology, I was still fascinated by the impacts of parrotfish feeding behavior and felt I had research questions I wanted to address. Returning to Bonaire to conduct graduate research feels like I have come full circle.

What is your top graduate school life hack or survival resource?

Graduate school can be a juggling act. You’re taking classes, working on your thesis, applying for funding, working a job (or a few), and still trying to maintain some semblance of a personal life. My “lab family” and cohort community were the most important survival resources for me throughout graduate school. My lab mate used to remind me that trying to get it “perfect” has diminishing returns and an impossible standard to manage. So, find your community and keep each other grounded. Whether it’s working on thesis writing together in a coffee shop or encouraging each other to go hike, climb or dive; that comradery is essential. Grad school is an important journey – not just a degree, thesis, or publications at the end.  

Any additional information or comments you would like to share?

Over the course of my master’s I had the pleasure of mentoring over twenty undergraduate
students. Their help conducting summer field research and benthic photo analysis was
invaluable. Working with them was one of the most rewarding parts of my master’s program and
this research would not have been possible without them. So, to any of them who read this –
thank you.

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