Increasing noise in the ocean affects right whales

First published in the MLA Newsletter, October, 2012.

We all rely on senses (sight, smell, taste, touch, and sound) to navigate our world. When one of those senses does not work well (i.e. limited sight in a dark room), other senses compensate. For right whales, sight is limited by the amount of light able to travel through the water. This allows whales to only see shadows and movements, not defined shapes or colors. Instead of depending on their limited sight to navigate their watery world, right whales and many other marine species rely on sound. Right whales communicate with various sounds to find mates, food, and to maintain the herd while migrating. If their ability to communicate is reduced, the right whales’ way of life could be in even more danger than it already is.

Unfortunately, the noise in the Gulf of Maine has been increasing for a number of years. “Noise levels in the ocean are increasing. It’s almost doubled every decade in the last forty years,” said Christopher W. Clark, MSEE PhD, I. P. Johnson Director, Bioacoustics Research Program at the Cornell Lab of Ornithology and Senior Scientist in the Department of Neurobiology & Behavior at Cornell University and co-author of a published paper on restricted communications for right whales. Sound travels more efficiently in water than it does in air, making noise, even miles away from the source, a loud threat to marine animals’ communication. Clark compares the noise to being in the city versus in the country. “When you are at camp out in the woods, it’s really quiet. You could hear a pin drop. You can easily have a conversation with someone. Then imagine trying to have that conversation while standing on the side of the street in a city. You have a lot more background noise making it harder to hear what the other person is saying.”

Clark said that right whales are now “all living in the city” because of the increased noise in the ocean. Where is all this noise coming from? “Almost all of the noise is coming from commercial shipping,” Clark said. “The sound from a ship can travel hundreds of miles underwater. As the ship moves farther away, sound decreases, but it decreases logarithmically with distance. That means at first, there will be a big decrease in noise. Then the rate at which noise decreases slows down.” He said that, for example, a nearby ship may produce 180 decibels. When that ship is one kilometer(0.6 miles) away the sound level drops to 120 decibels. But then at ten kilometers(6.2 miles)the level only drops to 110 decibels and at 100 kilometers (60.2 miles)it drops to 100 decibels. All of this translates into a lot of noise “smog” in the ocean allowing right whales very little space in which to communicate clearly. “We found that for at least 60 percent of the time whales are not able to communicate because there is so much noise,” Clark said.

Clark said that the May 2012 report he co-authored with Leila Hatch (NOAA) as the primary author, “Quantifying loss of acoustic communication space for right whales in and around a U.S. national marine sanctuary,” aims to alert people that increasing ocean noise is a critical problem. The researchers, in collaboration with National Oceanic and Atmospheric Administration (NOAA), recorded noise in the Stellwagen Bank National Marine Sanctuary during the spring of 2008 using marine autonomous recording units (MARUs), also called pop-up buoys.