Underwater mikes monitor Arctic marine mammals
Ricardo Antunes has been eavesdropping on strategic conversations of sea mammals in the northern Bering Sea. This is not new. The Wildlife Conservation Society member has been dipping hydrophones into the waters with local help since 2013.
The WCS’s marine acoustic monitoring program studies predicts increased ship traffic, with its increased noise and risk of collision likely will affect marine mammal communication in the Bering Sea—bowhead whales, beluga whales, walrus, bearded seals, ribbon seals, other marine mammals.
Fishing boat captain Adem Boeckmann of Nome has been transporting Antunes, his crew and equipment on the F.V. Anchor Point to areas of study near King Island, Diomede Island and near the villages and capes of St. Lawrence Island. Traditional hunters in the Savoonga and Gambell have been aiding Antunes with observations and historic hunting perspectives. Perry Pungowiyi of St. Lawrence Island has assisted.
Antunes’ work is related to changes in shipping and industrial use of Arctic waters associated to rapid climate changes and changes in habitat use for Arctic marine mammals. He is recording life sounds of sea mammals that he thinks they are making during important life’s work: hunting for prey, mating season, migration, even searching for a calf.
Antunes’ work will provide biologists a baseline to assess the effects of an upcoming increase in noise from shipping and resource recovery activities, for examples, that will affect Arctic marine mammals.
Slides of studies covering the period 1979 through 2017 show much less sea ice than now, and a decrease in sea ice from the late 1800s to present.
“The decrease in sea ice has consequences in terms of human activity,” Antunes said. “There are spaces through which ships can pass from the Atlantic Ocean to the Pacific Ocean over the Arctic Ocean. Reserves of oil and gas have also become assessable to exploration.
The sound from the underwater microphones feeds into an acoustic processing system, which can generate visible graphs, spectrograms and charts for study.
Noise will happen
Melting ice has allowed vessels to ply Arctic waters in new shipping routes, such as the Northern Sea Route, Northwest Passage, Transpolar Route, Canadian shipping routes. Vessels using all these routes will go through the Bering Strait coming or going and enter the Bering Sea, the Chukchi, the Arctic Ocean and the Beaufort Sea, and other northern waters where sea ice previously has blocked shipping routes and industrial noises. The WCS acoustic monitoring system has several listening devices deployed along an agreed shipping route through the Bering Strait.
“The most intense traffic is through the narrow Bering Strait. Any ships going ocean to ocean have to go through the Bering Strait, a narrow gap shared by many species and migrating marine mammals,” Antunes continued. “For example, migrating bowhead whales, who spend winter in the northern Bering Sea, then in spring go from the northern Bering Sea to the Chukchi and Beaufort seas, then back to the Bering Sea in the fall, through the narrow gap.”
Antunes is a postdoctoral fellow with the WCS. He has spent the last 15 years studying marine mammal ecology and behavior around the world, focused on acoustics.
Antunes spoke at the new UAF Northwest Campus Education Center in a Feb. 1 Strait Science Series session. He has been studying also marine mammals in offshore waters of New York. Students there are helping to interpret the acoustic data.
Sharing vital knowledge
The studies will be available for those concerned with recommendations on management strategies for marine mammals in the Bering Strait region—International Whaling Commission, Eskimo Whaling Commission, the U.S. Coast Guard, as well as coastal communities in the region. It is an area where there is an acknowledged lack of information on the effects of human-produced sound on marine mammals.
The Bering Sea provides more than half the wild-caught seafood consumed in the United States, plus three-fourths of the subsistence harvest feeding Alaska Natives and others living in coastal communities. There is concern that industrial sound could disrupt migration routes.
“Marine mammals are acoustic animals,” Antunes observed. “The are in an environment where sounds are transmitted more easily than in air. Ships are very noisy. Therefore ships have the potential to interfere with marine life with the production of noise, as shown around the world with marine mammal studies.”
Antunes showed a slide of a study where grey whales in waters of the western United States altered their paths to avoid sound introduced under water and then reclaimed their routes when the sound stopped.
Antunes presented slide media dealing with masking studies.
This information deals with how noise interferes with an animal’s ability to detect, interpret or discriminate an important sound, for example, cues and communication in locating food, listening for predators, foraging, migration, navigation and mating activities. Scientists have found masking has the greatest impact when the frequencies of the interfering sounds are similar to biologically important signals, such as mating calls. Ship noise that masks signals comes from the sounds of ship machinery coming through the hulls and the sounds of propellers, according to Antunes.
The mammals’ sounds and the recordings are “telling us the sensitivity to masking. The mammals put a lot of effort into sounds,” Antunes said. Human-produced sound has the strongest impact in terms of masking or interfering with biologically important signals, he said. On the other hand, sea ice has a quieting effect on the environment and strongly affects mammals’ presence and calling.
Scientists can track ships by a system that transmits their location and relates their routes to the data gleaned from acoustic monitoring, according to Antunes.
Antunes played recordings of marine mammals’ distinctive sounds. Walrus sounded like knocks and clapping; bowhead whales made low, then high, then undulating sounds; bearded seals to this listener sounded like crickets, then a squeaky wheel slowing down, going lower in pitch, then chirping.
The sea mammals reveal their presence during seasons of the year with their songs, therefore allowing Antunes and other scientists to increase knowledge of migrations, learning when the mammals congregate around St. Lawrence Island, or Diomede Island, near shipping lanes, or when melting sea ice allows them to return to feeding grounds and then return south.
“We are beginning to get a picture of what is happening out there with noise and marine mammals,” Antunes said. “With the baseline, we will be able to track the advance and levels of impacts of increased human activity on marine mammals.”