Intended as a tool to study the subtle effects of global warming, the North Pacific Acoustic Laboratory (formerly known as ATOC) has received far less attention than its noisy big brother, SURTASS LFA. In fact, many of the comments sent to Scripps Oceanographic Institution had to do with LFA concerns.
Like SURTASS LFA, the NPAL project has military connections. A large part of its funding came from the Defense Department’s Advanced Research Projects Agency. Then in the spring of 1999, when funding shortages threatened to end the program based at Scripps, the Office of Naval Research stepped in. To reflect the change in funding, ATOC was renamed NPAL-at the Navy’s request. The terms of operation remain the same, but the project has been expanded beyond studying temperature change and the effects of sound on marine mammals to include sound propagation studies.
The project got off to a rocky start. First, an early test in 1991 created some ripples: Conducted for 10 days off Heard Island in the Indian Ocean, the sounds-some 220 dB at the source and detected by receivers more than 11,000 miles away-silenced the local population of sperm whales. Only after testing did they resume vocalizing.
Then, in 1996, Scripps applied to the Hawai`i Board of Land and Natural Resources for an after-the-fact permit to lay about 27.8 miles of cable, which had been placed three years earlier along the ocean floor from the Navy’s Pacific Missile Range Facilities at Barking Sands, Kaua`i, to a boom box roughly eight miles north of Hanalei Bay. (For a full history of the project, see the April 2000 and April 1996 articles in Environment Hawai`i.)
The BLNR permit was to expire September 30, forcing the removal of the cable. On June 22, the BLNR granted an extension-the third-to leave the cable in place until September 2002. Department of Land and Natural Resources staff justified the time extension by noting that it would not require the installation of any new equipment, that because the cable has been lying on the seafloor since 1993, it has probably been “integrated it into the seafloor environment” by “natural processes,” and that the cable is deep enough not to interfere with other uses of the area.
The cable is just the silent partner in the NPAL project. Whether that cable will ever power the sound source that sits a little over 800 meters below the surface lies in the hands of both the Land Board and National Marine Fisheries Service. DLNR staff noted that the extension was needed to allow additional time to review the environmental impact statement, published this May. A decision regarding a Conservation District Use permit to allow a five-year run of the NPAL project is expected in October. At the same time, NMFS is deciding whether to grant NPAL a small take exception under the Marine Mammal Protection Act and the Environmental Species Act.
With the sound source’s long tenure in a fixed position, roughly half a mile from the boundary of the Hawaiian Islands Humpback Whale National Marine Sanctuary, the cumulative effect is one of the most important issues. “Even if you’re not close enough to it to rupture your cells, being exposed to that kind of sound over time is stressful,” says Marsha Green, a whale researcher from Albright College, who has been studying Hawaiian humpbacks for nearly 20 years. “Lots of studies show that noise is stressful on people, so why wouldn’t it be for cetaceans? Hearing is their most important sense.”
The box will broadcast at a source level of about 195 dB and a very low frequency of 75 hertz. Its five-year operation schedule will consist of six 20-minute transmissions-one every four hours-every fourth day, with each transmission preceded by a 5-minute ramp-up. The location allows convenient access to the Navy’s facilities, notably a power source, and it allows the boom box to transmit through the so-called deep sound channel, the 800 to 900 meter-deep layer of water that catches and transmits sounds much farther than shallower parts of the ocean. But these waters are also prime for humpback whales, although, according to surveys by Joseph Mobley from the University of Hawai`i at West O`ahu, the area around Kaua`i has one of the lowest proportions of cow and calf pods of all the islands.
For the most part, the sounds produced are constrained to within the sound channel. But some marine mammals, such as sperm whales and elephant seals, are known to frequent this depth. Also, not all sound remains trapped in the channel. For this project, Scripps has established the threshold risk of harm at 180 dB-the same level established for SURTASS LFA. Susie Pike Humphrey, project coordinator of NPAL, acknowledges that this level is “a real moving target. As they get more research that number keeps changing.”
According to the EIS, the most common baleen whale in the region, the humpback, won’t receive sounds that high because it doesn’t dive deep enough to encounter them. It indicates that even the deepest known humpback divers (about 250 meters) directly above the sound source would receive levels less than 140 dB. Most whales in the area are expected to receive levels less than 120 dB, it concludes. The deep divers who frequent the area are sperm whales. But they’re thought to be able to hear low frequency ATOC sounds well.
The potential effects of these low frequency sounds is far from cut and dried. In 1992, Scripps awarded Christopher Clark of Cornell University’s Bioacoustics Research Program a grant to develop and direct a Marine Mammal Research Program to study the effects of ATOC sounds. Sperm whales, humpback whales, and elephant seals were the only animals studied in the field. In the lab, rockfish were exposed to a maximum of 153 dB while researchers looked at immediate effects of 20-minute playbacks. They found no statistically significant responses.
Clark and his colleagues began baseline studies in 1993 of humpback whale behavior (including singing) and distribution off the north shore of Kaua`i. While their EIS mentions the presence of endangered turtle species at the site, MMRP scientists presented no specific results for studies of hearing or behavioral observations on any turtle species.
Mobley and his colleagues surveyed the waters within a 40-km radius of the source during 1994 when the sound was off, and during 1998 when the sound was on. “We examined two variables: distance of the whales from the ATOC source and distance offshore,” he explains. The mean distance offshore and distance from the source were both slightly greater during 1998, but those differences were not statistically significant, according to Mobley. “So we concluded that the ATOC transmissions did not affect humpback whale abundance in that area. If whale densities were to change on the order of 20 percent or more north of Kaua`i, we would be able to detect it.” According to Clark, more variability in animal behavior was explained by day-to-day traffic in the harbor and bay than by the broadcasts. Clark noted weekends on the Kaua`i coastline when helicopters flew over whales 90 times.
Studies off the Kaua`i and California coasts did not find “overt changes” in behavior for elephant seals or sperm whales during playback of ATOC-like sounds. For humpbacks however, dives during playbacks were longer in duration and distance – a fact the EIS uses as support that the noises did not stress the animals since they were increasing their received levels of sound, rather than surfacing away from it.
The EIS acknowledges that the MMRP does not provide sufficient information to draw conclusions about long-term effects on marine animals. To address this point, Scripps has added additional marine mammal monitoring and aerial surveys to the plan. This was, in fact, the only significant difference between the draft EIS and the final EIS.
Leading the anti-NPAL project locally is Ray Chuan, co-chair of Kaua`i Friends of the Environment. “They themselves claim they don’t know the long-term effect yet,” he notes. “It’s just a matter of time before it will do some harm.”
Many commenters-including the Department of Land and Natural Resources, former whale sanctuary manager Allen Tom, and the U.S. Fish and Wildlife Service-have recommended that the ATOC sound source not operate during breeding seasons of humpback whales and sea turtles. But Scripps notes in its EIS that doing so would “severely reduce the utility of both the acoustic thermometry and long-range propagation studies…. Since neither the California nor the Kaua`i ATOC MMRP found any overt or obvious short-term changes in the abundance or distribution of marine mammals in response to the transmissions… it is not anticipated that overt short term changes in abundance or distribution would result from continued use of the ATOC sound source.”
If the Kaua`i plan fails, Scripps has proposed an alternate, but unpopular, location: Midway Atoll, where Hawaiian monk seals and Bryde’s whales are common. Paul Henson, field supervisor in the Honolulu office of the U.S. Fish and Wildlife Service, wrote in his comments regarding the draft EIS: “We also strongly disagree with the alternative to relocate the sound source to Midway due to the sensitive nature of the Midway Atoll National Wildlife Refuge.”
Chuan is rallying the troops to attend the Land Board hearing on the permit, which he believes will be scheduled some time next month. He’s also working to have the board hold more than one hearing with at least one held on Kaua`i. “To us ATOC was always just the beginning,” says Chuan. “It is a fig leaf for the Navy. If it passes, it will open the door wide for other sonar technology.”
— Gretel Schueller
Volume 12, Number 2 August 2001