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How sonar technology is expanding our ocean understanding

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Using advanced sonar technology to reach the ocean's depths, marine biologist Kelly Benoit-Bird is expanding our knowledge about the way the sea -- and its many creatures -- function.

Using advanced sonar technology to reach the ocean's depths, marine biologist Kelly Benoit-Bird is expanding our knowledge about the way the sea -- and its many creatures -- function. An associate professor of biological oceanography at Oregon State University, Benoit-Bird was named a MacArthur fellow last year for her efforts. We spoke recently about the technology -- and motivation -- behind her work.

How do you use acoustic techniques to monitor the behavior of ocean creatures?

Most of the work I do involves sonar, which is sending out a sound and listening for it to return after it bounces off things in the water. Most people are familiar with this as a fish finder on a boat. We use exactly the same principle, but with a more sophisticated instrument to be able look at where things are, what species they might be and how they're moving through the water. We do that in lots of different places around the world. We're looking for everything from how many animals there might be to where they are in vertical space in the water. How are they moving up and down? How are they interacting with each other? What is their small-scale behavior like in terms of trying to avoid predators that are closing in on them? How are they working together to get prey? Conceptually, it's pretty simple in terms of the technique.

What sounds are you listening for exactly?

It's the sound we're making. We're listening for it to bounce off of [the sea creatures]. We're making echoes from sounds we make.

You created new devices to do this work. Talk about how you developed them.

In some cases, we developed sonars that use very different signals than are typical. In one case, we've actually built a sonar that uses a click, much like a dolphin. We modeled it after the dolphin instead of a more artificial human sonar. We know that [dolphins] are very good at using sonar, so we basically stole some ideas from them.

In other cases, we've developed instruments that can go on different platforms than are typical. We've been doing a lot of work on remote autonomously operating vehicles and trying to develop sonars that can be self-contained and make decisions for themselves while they're on these instruments. We're also developing new ways of looking at data, so that we're able to do things like look at the behavior of individual copepods, which hasn't been possible with the commercial instruments available.

How much of the device development do you do yourself?

With the instruments, I'm involved in the design, most often in the construction and in all of the testing and data analysis and development. When I was a graduate student, it was all about me. I didn't have any help. Now that I have a larger research program, I do have other people involved in working on this.

Talk about what you've learned about sea creatures throughout your research career.

We've worked in lots of different places. There are a huge number of things we've learned about each of those systems. But one of the larger patterns that continues to emerge from all those systems is how important space and time is. Animals aren't evenly distributed in the ocean and they behave very differently at different times of the day. It's those variations in both spatial structure and temporal variation that are important to how the ocean works. That presents some interesting challenges for us in how we sample because we have to be able to characterize often very small spatial structures and short time scale behaviors. But those are what's important in how animals are interacting with each other.

How did you get into this field?

I've always been really fascinated by the ocean and I love learning new things. Learning new things from a book is interesting, but learning new things that no one else knows is a very satisfying experience. We get to be explorers, despite the fact that we're not finding new continents anymore. We know so little about the ocean relative to even the moon.

How I specifically got interested in doing the kind of science I do is a combination of my background and educational experiences. I'm really interested in being hands-on. I love to build things and break them and fix them. I love going to sea where you have nobody to count on but yourself. As an undergraduate, I was fortunate enough to work in a fantastic lab that did work in acoustics. I got really excited about the concept of using sound. At the same time, my degree is in ecology, which is about how different parts of the environment interact with each other. Not very many people were using [sonar in the ocean] to ask the questions that were being asked in other ecosystems. Why is this animal here and not there? How does this animal survive? Who eats whom? It gave me an opening to apply what I'd been working on with acoustics to the questions I found most exciting.

What's next for you and your work?

My research group is going in several different directions right now. We're focusing quite a bit on Humboldt squid. They're typically found in warm water, so we've been doing some work studying their ecology in the Gulf of California and trying to understand how they're able to exploit habitats that have very low oxygen levels. One of the interesting problems is that they've increasingly become common all along the West Coast. We're wondering why and how they've been able to do that and what the ecological consequences are.

We're trying to do big-scale synthesis work in Hawaii, which I've been working on since I was a graduate student. [We're trying to understand] how physics drives the productivity of plant life in the ocean and how that affects the small animals and the fish. We're finding that the spatial structure is absolutely critical in determining that the outcome is. If you understand the physics, you can actually predict what's going to happen pretty far up the food chain.

We're also working on understanding how top predators in the Bering Sea find and use their resources. It's not about how much prey is available to them, but where it is and when it's there that's important to how they forage. Ultimately, it comes back to that same question about why time and space matter.

Photo: Kelly Benoit-Bird / Courtesy of the John D. & Catherine T. MacArthur Foundation

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Christina Hernandez Sherwood

Contributing Writer

Contributing Writer Christina Hernandez Sherwood has written for the Los Angeles Times, Newsday, the Philadelphia Inquirer, Diverse: Issues in Higher Education and Columbia Journalism Review. She holds degrees from the University of Delaware and Columbia University's Graduate School of Journalism. She is based in New Jersey. Follow her on Twitter. Disclosure