BUSTLING SHIPPING LANES, deep water oil exploration, pile driving and military sonar exercises have made the ocean a pretty noisy place. According to scientists at the Bahamas Marine Mammal Research Organisation (BMMRO) excess noise in the ocean stresses marine mammals, interferes with their communication and navigation systems and can sometimes lead to death. “Most marine mammals communicate with acoustics, so they are using noise. It’s a simple equation. If the ocean is too loud for them, that creates a number of issues,” says BMMRO researcher Charlotte Dunn.
Scientists at the BMMRO are working with the United States Navy to understand what impact navy sonar has on marine mammals—especially beaked whales. The deep water near the Great Abaco Island in the Bahamas, where the BMMRO is located, is ideal habitat for beaked whales. This area also houses the United States Navy’s Atlantic Undersea Test and Evaluation Center (AUTEC) on Andros Island.
The two worlds collided on March 15, 2000 when at least 14 beaked and 2 minke whales ended up stranded in the shallow waters in the Northeast and Northwest Providence Channels of the Bahamas. Researchers found one beaked whale in front of the BMMRO research facility and were able to guide it back to deeper waters. Soon after, they heard of another stranded whale a mile away, and while they struggled to keep the second whale wet, they received notice of a third whale stranding. By the end of the day researchers became suspicious that this was not a normal mass stranding, and that the whales were desperately trying to get away from something.
“The alarms go off when you have a number of [species] stranding together. That suggests that it’s not due to disease. It’s something that changed in their environment,” says BMMRO researcher Diane Claridge, who helped rescue the stranded whales.
Later scientists found out that the United States Navy had been operating submarines and ships that day with sonar activity. The military uses powerful mid-frequency sonar to explore the ocean and its inhabitants. By sending out sound waves and deciphering how they bounce off objects, the military can search the ocean for suspicious activity.
Although researchers are unsure of why beaked whales are so sensitive to noise, they speculate that the noise causes behavioral changes. A sudden loud sound may frighten the whales and in their panic make them ascend or descend too quickly. A whale’s middle ear is full of air and, just like humans, they have to equalize in pressure during ascent or descent in the water. A rapid change can be extremely painful and damaging.
By studying beaked whales, Claridge and Dunn can provide the Navy with population and migration information. That way the Navy can plan their activities with the least amount of impact on the whales. Mass strandings have occurred in conjunction with military activity around the world in Greece, the United States and the Canary Islands. According to Claridge and Dunn, noise in the ocean is the number one concern for the health of all marine mammal species.