Discoveries in the Deep

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Mackenzie Gerringer, assistant professor of biology, at sea over the Mariana Trench, where she and other scientists discovered the Mariana snailfish, the deepest living fish in the ocean. /Photo by Paul Yancey/Whitman College

Marine biologist Mackenzie Gerringer studies the depths of the world’s oceans from the rolling hills of Geneseo.

By Robyn Rime

Down in the ocean’s trenches — far beyond the reach of sunlight — the deep sea is unimaginably dark, a world of frigid temperatures and immense pressures. Marine organisms manage to flourish in these harsh environments, and assistant professor of biology Mackenzie Gerringer studies how.

“I fell in love with the mystery of deep-sea habitats and was struck by how little we understand about them,” she explains. “That sense of discovery kept me exploring deeper and deeper, all the way to the bottom.”

So little is known about deep-water environments that almost every expedition uncovers something new. Gerringer, who earned a doctorate in marine biology from the University of Hawai’i at Mānoa discovered a new species with colleagues from the University of Hawai’i and Newcastle University, which they described in 2017. The deepest living fish in the oceans, it was found in the Mariana Trench in the western Pacific near Guam, where waters run deeper than Mt. Everest is tall.

“This fish lives deeper than any known vertebrate,” says Gerringer, “so finding it was very exciting.”

As an animal physiologist, Gerringer specializes in the life histories, feeding mechanisms and high-pressure adaptations that help deep-sea fishes survive in the ocean’s trenches. Her most recent paper examines high-pressure tolerances in deep-sea fish enzymes (The FEBS Journal, 6 April 2020).

“Pressures in the deep sea are very high. At the bottom of the Mariana Trench, pressures reach 15,000 pounds per square inch, about the equivalent of an elephant standing on top of your thumb,” Gerringer says. “I’m interested in how fish thrive under that high pressure.”

Gerringer’s lab at Geneseo is examining that and other questions, such as how other organisms survive high pressures, how long they live, what they eat and how they interact. Such research is possible even at land-locked Geneseo in part because, as Gerringer points out, “none of us live in the deep seas. We go to sea, take collections, then come back to the lab to do our analyses,” and in part because of the collaborative nature of deep-sea biology, which requires considerable resources.

Students in Gerringer’s lab are working on potentially describing three new species of deep-water snailfish by examining samples collected by colleagues from the University of Hawai’i at Ma-noa and the Monterey Bay Aquarium Research Institute. Small, tadpole-shaped snailfish species live around the planet, from intertidal zones to the deepest trenches. CT scans of the samples and examination under a microscope allow students to look minutely at the snailfishes’ bodies, or morphologies, and DNA sequencing will help them build genetic trees showing relationships to previously known species.

“We need both morphological and genetic evidence to describe a new species,” explains Gerringer. “If they’re new, we’ll be able to name them and publish a species description. But even if they aren’t new species, the students have had the chance to understand taxonomy, examine DNA sequences, take accurate measurements and learn 3D data processing.”

“Adding to the understanding of biodiversity present in the deep oceans has been incredible,” says biology major Jessica Palmeri ’21. Adds Brett Woodworth ’22, also a biology major, “It’s an unusual opportunity to potentially play a part in discovering new species of fish.”

Exploring the ocean’s mysteries — as vital as that goal may be — is, in the end, only part of Gerringer’s intention. “I hope students can find a connection to the oceans and to deep-sea habitats that makes them feel a link with and responsibility for these vital and amazing ecosystems on our planet,” she says.

Read about how Geneseo and two professors are shaping the future of women and underrepresented groups in academia, especially in STEM fields.

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A CT scan of the Mariana snailfish. The small white bones in the inner ear are otoliths and can be used to estimate the age of a fish. /Photo by Adam Summers/University of Washington

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A CT scan of the Mariana snailfish. The green shape, a small crustacean, is seen in the snailfish’s stomach. /Photo by Adam Summers/University of Washington

Author: geneseoscene

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