August 16, 2012
NOAA Researchers Track Underwater Noise Pollution That Can Be Disruptive To Whales
April Flowers for redOrbit.com - Your Universe Online
Noise pollution is a problem that plagues us all. Loud cars and trucks, music, airplanes and more create a constant cacophony we have to learn to block out of our conscious mind in order to deal with our lives.
However, we aren't the only ones suffering from too much noise.
According to a paper published in Conservation Biology, high levels of background noise, mainly due to ships, have reduced the ability of critically endangered North Atlantic right whales to communicate with each other by about two-thirds.
From 2007 until 2010, scientists from Stellwagen Bank National Marine Sanctuary, along with other institutions, used an array of acoustic recorders to monitor noise levels, measure levels of sound associated with vessels, and to record distinctive sounds made by multiple species of endangered baleen whales, including "up-calls" made by right whales to maintain contact with each other.
The project was an effort to characterize the underwater acoustic environment of the Sanctuary and examine the effects of that noise on resident marine animals.
In April 2008, NOAA's Northeast Fisheries Science Center documented more than 22,000 right whale contact calls as part of the study. Software developed by Cornell's Lab of Ornithology in conjunction with Marine Acoustics Inc. aided in modeling ship noise propagation throughout the study area.
The research team deployed arrays of marine autonomous recording units (MARUs) to continuously record low-frequency underwater sounds from 10 to 100 Hz. This data was combined with vessel —tracking data from the U.S. Coast Guard's Automatic Identification System to calculate noise from vessels inside and outside the sanctuary boundaries.
MARUs are also being used to detect, locate and track vocalizing marine mammals such as North Atlantic right whales, humpback whales, fin whales and fish species such as cod and haddock.
Comparisons of noise levels from commercial ships today with historically lower noise conditions of nearly a half century ago, allowed the team to estimate that the right whales have lost an average of 63 to 67 percent of their communication space.
"A good analogy would be a visually impaired person, who relies on hearing to move safely within their community, which is located near a noisy airport," said Leila Hatch, Ph.D., NOAA's Stellwagen Bank National Marine Sanctuary marine ecologist. "Large whales, such as right whales, rely on their ability to hear far more than their ability to see. Chronic noise is likely reducing their opportunities to gather and share vital information that helps them find food and mates, navigate, avoid predators and take care of their young."
North Atlantic right whales, which live along the coast from Nova Scotia to Florida, are a type of baleen whale with callosities on its head, a broad back without a dorsal fin, and a long arching mouth. They are on the brink of extinction, with only 350 — 550 believed to still live along the Atlantic coastline.
"We had already shown that the noise from an individual ship could make it nearly impossible for a right whale to be heard by other whales," said Christopher Clark, Ph.D., director of Cornell's bioacoustics research program and a co-author of the work. "What we've shown here is that in today's ocean off Boston, compared to 40 or 50 years ago, the cumulative noise from all the shipping traffic is making it difficult for all the right whales in the area to hear each other most of the time, not just once in a while. Basically, the whales off Boston now find themselves living in a world full of our acoustic smog."
A world full of acoustic smog sounds delightful, right? Think Times Square on New Year's Eve, but every day and every night while you search for a mate, your family, and a way to feed yourself.
The authors suggest that the impacts of chronic and wide-ranging noise should be incorporated into comprehensive management plans to limit the cumulative effects of offshore human activities on marine species and their habitats.
"We are starting to quantify the implication of chronic, human-created ocean noise for marine animals," said Holly Bamford, deputy assistant administrator of the National Ocean Service. "Now, we need to ask how we can adapt our management tools to better address these problems."