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# **Listen Up:** What you need to know about ocean noise.

# Making Waves: Episode 138

### *Many marine organisms, including marine mammals, sea turtles, fish and invertebrates, rely on sound and hearing for their survival. Over the last century, increases in human activity within our ocean have led to increasing levels of noise. This increasing amount of noise from human sources is a rising concern for the health and well-being of marine organisms and ecosystems. In this episode, we talk with NOAA marine ecologist Dr. Leila Hatch about her work to better understand the ocean soundscape by developing programs that can establish baselines, detect changes in noise levels, and support the design of methods to reduce noise impacts.*

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### Transcript

HOST: Welcome to Making Waves – a podcast from the NOAA National Ocean Service.  I'm Megan Forbes and today we'll be talking about Ocean Noise... when you think of the ocean, you might imagine a vast underwater world filled with strange and wondrous sights & creatures... but do you think about sound?  It is a big part of marine life, as sound travels faster underwater and can be heard farther across the miles than above the surface, even by the human ear.  

Sound is a fundamental component of ocean life that many marine animals and ecosystems have relied on for millions of years. In just the last 100 years, human activity has increased along the coasts, further offshore, and in deep ocean environments. Noise from this activity travels long distances underwater, leading to increases and changes in ocean noise levels.

Rising noise levels can negatively impact ocean animals and ecosystems in complex ways, reducing an animal's ability to communicate and to hear environmental cues that are vital for survival.

NOAA and the Office of National Marine Sanctuaries are approaching this issue by aiming to reduce negative physical and behavioral impacts to species, as well as conserve the acoustic quality of their habitats.

To learn more about this issue, I spoke with Dr. Leila Hatch - a marine ecologist based at the Stellwagen Bank National Marine Sanctuary in Massachusetts. Her work focuses on acoustically-sensitive marine species and the impacts of underwater noise in the sanctuary, and she provides support on noise science and policy for other sanctuary sites. She's also the co-lead of the NOAA Ocean Noise Strategy. I asked Leila to tell us a little bit about how the ocean noise produced by human activities affects marine animals.

LEILA HATCH:  Sound is an incredibly effective way for marine animals to communicate.  A wide variety of marine animals make sounds to communicate to one another.  And beyond using sounds to talk to one another, animals hear – and marine animals have particularly evolved to use their hearing in a great diversity of ways.  They listen for food and the sounds made by their prey as it moves through the water, they listen to the echoes of environmental sounds – winds and waves – and the sounds they make against topographic features (underwater/undersea mountains) – which tells them about areas where fish may school, or where algae and zooplankton may cluster in upwelling.  Those are all very predictable places for animals to find food, and they have an acoustic echo.  They listen for their predators, and they listen to each other.

People also do a great many things offshore, and many of them make sound. Sometimes that sound is a bi-product of things that we are actually doing – we're moving all of the world's goods on large commercial ships, and that maritime traffic which is how we transport over 98% of the world's goods around the globe, we do that almost entirely on ships.  Those ships have propellers, when they spin produce bubbles, and when the bubbles burst (they) make an acoustic signature – they make a sound.  That sound has a deep, low frequency – those lower tones below what humans hear well – that low tone made by all those ships moving all that stuff around, its leading to a rise in noise level.  People have used sound to communicate underwater between different ships, we also bounce sounds off of the crust of the earth to get a better understanding of what's below including oil and gas deposits.  So we make sounds on purpose, and those sounds also can lead to a rising level of background noise.  This combined, increasing level of human activity offshore, much of which makes sounds, has lead us to an understanding that the ocean's acoustic environments are quite different than they were when ocean animals evolved their systems to use the acoustics of their underwater environments. 

Our job is to understand how that change in the acoustic quality of these places where animals live is affecting them.  We're particularly concerned about their ability to hear one another at times that are very important in their life histories.

HOST:  Are we creating more noise now than ever?

LEILA HATCH: There are very few places in the world's oceans where we have been measuring in a standardized way how much noise there is in the ocean over time.  But in the places where we have measured, such as off the central California coastline where we've been measuring since the 1940's and 50's, and we also can still make those same measurements in the same place today, the rise in the levels of background noise at very low frequency tracks very well with the growth of commercial shipping traffic and the quantity as well as size and gross tonnage of what we're carrying across that ocean basin.  That trend is not as distinct in every place as we go to look around at the oceans, but again we don't have that timeline in such a calibrated and careful way in all of the places where we'd like to make those measurements.  A lot of what we're doing now is trying to fill in an understanding of what today's background noise conditions look like as well as anything we might know about what they looked like historically.

HOST: Dr. Hatch has dedicated much of her life to this specific issue, and I was really interested in finding out why this particular issue was so important to her, personally.

LEILA HATCH:  I grew up spending my time on a small farm and also offshore visiting my grandparents on an island.  Those two environments exposed me to a lot of days both in the water and looking at tidal marine life, and listening and out in natural spaces in a rural environment.  My father was a musician, and I think for that reason I spent a lot of time listening in those places.  When I then met somebody who was a renowned researcher of whale calling behavior, those two things came together for me....an understanding that the world could be listened to, and the fact that  huge animals in a marine environment that I didn't experience were calling to one another became fascinating to me.  From the very beginning of studying whale vocalizations, I was exposed (to) and thinking about human effects on that behavior, and I've been very interested ever since in how we could change what we do in ways that would make more room for that animal experience to continue.

HOST: You are one of the leads of NOAA's Ocean Noise Strategy effort  - tell us a bit about what it is, and what it's doing.

LEILA HATCH: NOAA's Ocean Noise Strategy grew out of an interest in ensuring that over the next decade we're better addressing the effects of noise on more than marine mammals...from noise effects that are more cumulative effects of many types of human activities, as well as the chronic effects of rising background noise conditions and the types of sources that contribute to those.  A main focus of NOAA's Ocean Noise Strategy was to broaden the agency's approach to addressing noise impacts to not only account for those acute effects  - those sudden effects on an individual marine mammal – but to better understand and to design tools to address the effects on acoustic habitat.  Acoustic habitat simply means the acoustics of places.  Places that are of importance to and sustain marine species that rely on listening.  We call that the acoustic habitat of those creatures.

HOST: How does the National Marine Sanctuaries system factor into the NOAA Ocean Noise Strategy? 

LEILA HATCH:  So we discuss in the Ocean Noise Strategy the reasons that Sanctuaries are particularly important as sentinel sites for understanding acoustic habitat and for designing methods to better protect it.  The mandate in National Marine Sanctuaries focuses on holistic protection of ecological processes in these places that have been designated as important.  Ecological processes can include all the things that sustain a functioning ecosystem – all that inter-relatedness of predators and prey, and their environment.  Acoustics are inherent to that complexity.  They're inherent to how animals act with each other, as well as to how they interact with their physical space.  We consider Sanctuaries as fabulous test bed environments for working with partners to develop improved scientific methods so we better understand how it is that animals are both behaving acoustically in the sounds they are making, and how they are using their hearing to interact with their environment, and then as we understand that better – to design methods to protect the conditions that they need to survive.

HOST: What are some of your greatest hopes for an outcome of the Ocean Noise Strategy? What are possible solutions to the noise problem?

LEILA HATCH:  The Ocean Noise Strategy sets out a long-term vision.  It's considering methods that we need to have in place over the longer term and it acknowledges that it will take time to develop some of these methodologies.  This is an issue that needs a forward-looking approach for new technologies that can be designed with less of an acoustic footprint when possible...quieter technologies, quieter ships, quieter methods for gaining information...and that too will take time to engineer.  To be less about how individual animals are responding to individual stressors and more about how whole systems of marine life are supported by their environments and what it is about human activities that are compatible or less so with particular functions of those places...  The broader vision for promoting the Ocean Noise Strategy was to help people understand an aspect of being underwater that people don't experience in the same way that animals do.  Our ears don't function the same way underwater and our experience of hearing in air is not the same as animals' experience of sound underwater.  So it's hard to translate to people who are in fact the ones who need to protect this condition for animals.  Understanding the acoustics underwater has brought with it a greater awareness by people of their own reliance, as they walk through the world, of what they hear...has started to change the way they consider the byproducts of human consumption patterns and the choices they might make to alter those.  A lot of the things I'd like to see moving forward are both people's understanding that the local choices they make can contribute to the global problem, and that they in fact can have a local effect by some of the same choices that they are considering making their overall footprint on the environment...and then the support will be for governments to continue to work together collaboratively with the support of people to understand this problem and  to partner in ways that can track its global reduction.

HOST: Thanks to Dr. Leila Hatch from the Stellwagen National Marine Sanctuary for educating us on this important issue of Ocean Noise and its impacts to our planet's underwater world.  We appreciate you taking the time to learn with us, and hope you'll join us again for our next episode of Making Waves.  Until then...thanks for listening.

From corals to coastal science, catch the current of the ocean with our audio and video podcast, **Making Waves**. 

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