This article is in follow-up to Serena’s earlier post about NOAA’s emerging guidelines in marine mammal acoustic protection.
As Serena noted, marine mammals, including cetaceans (whales, dolphins, and porpoises), are constantly communicating underwater using sound waves. Humans have also begun to use sound waves underwater to make processes of mapping the ocean floor easier and faster, with SONAR. SONAR stands for SOund Navigation And Ranging. If you ever wondered how scientists figure out where oil and gas deposits are located under the seafloor (see map), sonar is your answer. Sonar is also very important in creating a general map of the seafloor and its bathymetry, or topography. On the continental shelf, this is how scientists and developers determine where there are good spots to build piers and moor offshore wind turbines. Sonar is a technology we developed that is incredibly more advanced than early methods of manual ocean depth measurement. The effects on marine mammals, however, seem to be more deadly than we previously thought.
Human created sonar waves have become much more prevalent, especially with the use of sonar navigation in the military. This accumulation of sound waves tends to disorient marine mammals, in the same way someone talking during class distracts you from your professor. Last September, a group of pilot whales made their way into a Scottish bay off the coast of Shetland Island, a shallow body of water that could have stranded the whales had they ventured too far inshore. They looked ‘battered and panicked’ according to the reporting Huffington Post article. Not five days later, a group of about 100 pilot whales in bad shape made their way into an Icelandic harbor, where they were consequently butchered for their meat. The supposed causes of these, along with many other similarly disturbing instances, seem to be confusion and social chaos that comes into a pod as a result of sonar activity associated with oil searches and offshore wind siting.
Knowing that sonar is such an integral part of most of our oceanic science, how can we reconcile the fact of the matter, which is that sonar is occasionally devastating to cetaceans and other marine animals in its path? Regulations on sonar use, like those mentioned by Serena, are a great starting point. The Navy, a main source of marine sonar activity, has agreed to employ a ‘Marine Mammal Observer’ and abstain from sonar training when vulnerable marine mammals are in the area. These solutions are ideal for areas and studies where sonar is the only option for gaining information. But increasing technological alternatives may play a larger role in eliminating unnecessary sound waves from ‘polluting’ the ocean. Passive sonar, a technique employed by submarines when they wish to remain undetected, involves simply ‘listening’ for existing sound waves, rather than emitting frequent pulses. Like many other forms of marine observation, satellite imagery can also be utilized in revealing water disturbances and mapping out the oceanic bathymetry. As our satellite capabilities increase, the benefits of this method may outweigh those of traditional sonar. The introduction of sonar to our scientific capabilities was a boon for marine geologists and seafarers alike, but in areas of high use, it has become harmful to oceanic ecosystems. It’s time we looked at alternatives before whale beaching becomes a common sight on our coastlines.