Astrid Leitner shines light on the deep, dark sea
By Nancy Steinberg
Fall/Winter 2023
When scientists deploy instruments by tossing them over the side of a ship, they truly never know what will happen next. If all goes well, they easily collect that zooplankton sample or temperature reading with little to no drama. Or, they could lose the piece of equipment entirely. It happens. It’s very upsetting.
Astrid Leitner was thinking that her outcome was somewhere in the middle. She had deployed a baited camera trap to the summit of a previously unmapped and unexplored underwater mountain in the Pacific Ocean thousands of meters below, and waited hours for it to touch down. The bait would attract animals to a video camera so she could learn who was there and in what numbers. But when she retrieved the camera, something seemed very wrong.
“I thought the camera had failed, because the thumbnail image was so dark,” she says.
A closer look at the video revealed that in fact the camera had worked just fine. The thumbnail looked black because it was actually crowded with hundreds of deep-sea cutthroat eels, all attacking the bait in a writhing mass.
“No one had seen anything like that before,” she says. When it comes to Leitner’s work, this seems to be a common refrain.
New to the faculty in the College of Earth, Ocean, and Atmospheric Sciences, she studies how features of the topography of the deep seafloor, such as canyons and seamounts, affect abundance and distribution of fishes and other organisms. She frequently studies places in the ocean where no one has been, or even mapped. This is not just “cool” science — these regions of the ocean provide us with many products and services ranging from fish to pharmaceuticals, Leitner points out, and we need to understand them before they are overly impacted by resource extraction.
Having begun her life in landlocked Austria, how did she come to study not only the ocean, but the deep, dark part of it?
Leitner moved to California as a young girl and immediately fell in love with the ocean, she says, and later set out to study it in college and beyond. Two factors led her deeper and deeper into the abyss. One was a parallel interest in exploration and discovery, including ocean mapping — she holds undergraduate degrees in both marine biology and Earth and planetary sciences from the University of California, Santa Cruz, giving her insight into aspects of undersea landscapes. The other was a summer research program here at Oregon State.
As an undergraduate, she spent one summer as an NSF-funded Research Experience for Undergraduates fellow at OSU’s Hatfield Marine Science Center, where she worked with fisheries biologists Waldo Wakefield and Ric Brodeur. They gave her some unanalyzed video data gathered by a remotely operated vehicle in the Astoria Canyon, a deep-sea feature off Oregon, and she was hooked, intensely intrigued by these understudied and fascinating places.
Her subsequent work in graduate school at University of Hawaii and as a postdoctoral fellow at the Monterey Bay Aquarium Research Institute helped her hone her focus on the effects of steep and dramatic undersea features on deep-sea community ecology. Leitner’s work asks, what species use various abrupt deep-sea habitats? What are they doing in these habitats? How do the observed species interact with each other? How does community structure change over space and time?
In order to study such mysterious and remote ecosystems, Leitner uses a variety of techniques to ask overlapping questions. “Each approach has its own bias,” she says, “So to get around that, you look at the environment from as many perspectives as you can to get as close to the truth as possible.” Baited camera traps, like the one that captured the eel video, give her a stationary snapshot. She also uses autonomous vehicles and remotely operated vehicles to move around in the environment and collect samples, satellite data to study the overlying surface ocean conditions, and traditional oceanographic instruments to learn about currents and ocean chemistry at these deep-sea features. She has recently added a new technology to her quiver: active acoustics, in which sound is used to create pictures of underwater features, from canyon walls to fish aggregations.
She has been to the ocean’s depths in person only once, aboard the famed submersible Alvin, operated by the Woods Hole Oceanographic Institute. She says that the submersible crew joked that they needed extra oxygen on her dive to compensate for how much she was using due to her excitement.
“It was like a walk in the woods for a terrestrial ecologist. Imagine studying a forest from videos: It’s very different than being there, watching the trees move in the breeze and the animals interacting with their environment in three dimensions,” she says.
Her recent research has focused on the Clarion-Clipperton Fracture Zone, an expansive abyssal plain in the Pacific between Hawaii and Mexico dotted with seamounts, hills and other features. Her work there has revealed that in general, more individual organisms and a greater diversity of species are found at places with a lot of bathymetric relief, compared to areas that are relatively flat or featureless.
A new project focuses on animals in the mid-water, rather than on the bottom, of the Monterey Canyon off the California coast. Leitner explains that many animals, such as zooplankton and the animals that feed on them, make daily migrations from the deep sea to the surface, coming up to feed at night and hiding in the dark depths during the day. What happens when these animals encounter a canyon wall? She intends to find out.
It is critical to learn about the deep ocean, Leitner says, because we need it. For example, it plays a critical role in locking away carbon that originates in the atmosphere, a key function in this time of climate change. And importantly, humans are having a range of effects on this ecosystem via activities like fishing and mining. “We’re impacting a system that we don’t even understand,” she says. “Without more information, how will we regulate those activities appropriately? If we go in blind, chances are that we’re going to do some serious, long-term environmental damage.”
“We’re all connected to the deep sea,” she continues. “There is no line in the ocean that says to us, ‘below this, nothing matters.’ The ocean is all connected. It’s the largest livable habitat on the planet.”
With Leitner’s work, we can get to know it a little better.
