An experiment on the ocean which was conducted accidentally
in the middle of the shipping silence after September, 2011 has shown the first
direct link between aquatic noise and stress in whales, researchers reported.
The results indicated that a drop in a hormone related to
stress, was found in whales when a reduction in ocean noise occurred that
followed a near-standstill in ship traffic, due to security concerns following
the attacks.
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| Photo credits: Smithsonian |
The research indicates that whales and other aquatic life
that communicate by sound and travel can be harmed by the noise. This research
leads to more research and eventually can influence future ocean traffic and
development, said New England Aquarium scientist Rosalind Rolland, the report's
lead author.
"This is definitely a very important piece in the
puzzle that lends credence to the idea that, yes, we potentially have a problem
out there and we need to learn a lot more about it," Rolland said.
The report is based on data combined from two unrelated
experiments in Canada's Bay of Fundy that happened to be occurring simultaneously.
One experiment involved acoustic recordings of right whales; the other involved
the collection of whale feces samples, which contained hormones related to
stress.
It wasn't until 2009 that Rolland realized the
information existed for the analysis, published Wednesday in the British
journal Proceedings of The Royal Society B.
"Here is the first solid piece of evidence that says
there's a link between noise level and stress," said Christopher Clark,
director of the bioacoustics research program at the Cornell Lab of Ornithology,
who was not a paper co-author. Clark noted that stress has long been related to
longevity, reproduction, disease and other major health indicators in whales.
There's no international standard for ocean noise levels and
it is very difficult to know what kinds of problems it causes, Rolland said.
The use of military sonar at sea has been one source of
tension between governments and environmentalists, who assert that such sounds
kill whales and other aquatic life.
The Bay of Fundy is predominantly bordered by the
Canadian provinces of New Brunswick and Nova Scotia. Rolland was there in
September 2001, taking right whale fecal samples in the middle of a study on
the health and reproduction of the endangered North Atlantic right whale.
She remembered getting word at the waterfront of the
terror attacks, then seeing her crew in tears as they watched the coverage. It
was a brilliant day, and after a while, the crew decided to go on with their
work, as a measure of defiance and also because the bay was "calming for
the soul," Rolland said.
"It's like our cathedral," she said. "It's
a beautiful place."
That day and those following were like a primal ocean
scene, Rolland said. "There was nobody out there except for us and the
whales."
Around the same time, another researcher, Susan Parks,
was getting acoustic recordings on mothers and their calves for research on the
social behavior of the whales.
The information didn't come together until late 2009,
when Rolland started researching stress and underwater noise to prepare for a
workshop organized by the Office of Naval Research. She realized Parks had four
days of sound recordings from the bay, two days before and two days after Sept.
11, and she had five years of data on stress hormone levels for the whales that
included that time.
A hunch, and then quick analysis by Rolland, showed a correlation
between a drop in sound and the drop in whale stress hormone levels. The naval
office eventually agreed to fund the work that led to the paper, she said.
The more rigorous analysis showed a significant decrease
in background noise in the bay post-Sept. 11, including a drop in the low
frequency sounds that ships emit and which the whales use to communicate.
Scientists compared the stress hormone levels in the
whale feces during the five-year period and found them to be markedly lower
only during the time when ship traffic was down immediately after 9/11.
Rolland said provision of specific stipulations come with
any study done accidently. A study that has been planned would have had more data
related to noise and hormones. This study apparently can't be repeated. And
it's also imprecise how much chronic stress the whales can take from noise before
the population is affected, largely because it's impossible to conduct
controlled experiments on 50 ton animals.
But even with the provision of specific stipulations,
Rolland said, "It's pretty good evidence. We have no other explanation for
these findings."
Journal Reference:
1. R. M. Rolland, S. E.
Parks, K. E. Hunt, M. Castellote, P. J. Corkeron, D. P. Nowacek, S. K. Wasser,
S. D. Kraus. Evidence that ship noise increases stress in right whales. Proceedings
of the Royal Society B: Biological Sciences, 2012; DOI: 10.1098/rspb.2011.2429
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