What’s happening? Whales react to human-caused noise pollution, including from military sonar systems, similarly to how they respond to the sounds of predators, according to a University of St Andrews-led study. The analysis focused on four whale species. It found that noise pollution caused the whales to stop feeding, potentially weakening them and leaving them more vulnerable to predation. The more a whale was exposed to sonar sounds, the less it foraged.
Why does this matter? Underwater noise pollution is growing with increased human activity in the ocean, whether that is related to shipping and fishing vessels, clean energy infrastructure, fossil fuel projects or naval sonar systems. Identifying the marine species that are at risk from noise disruption can play a key role in finding ways to mitigate the issue, particularly given there is currently no binding international standard to regulate noise pollution in the ocean. The above study centered its exploration on long-finned pilot whales, northern bottlenose whales, humpback whales and sperm whales. Cetaceans – aquatic mammals such as whales, dolphins and porpoises – are particularly vulnerable to human noise pollution as their hearing abilities can result in them misidentifying these sounds as representing danger, such as from a predator. Ocean noise pollution also disturbs the “blue corridors” used by whales for seasonal migration, a separate report from WWF found earlier this year. On a broader level, human behaviour could also be causing endangered North Atlantic right whales to become smaller while limiting their ability to reproduce. Contributing factors include shifting food availability, collisions with other ships and noise pollution. Wastewater released from exhaust-cleaning scrubbers on ships that use an open-loop system pumping water and contaminants into the ocean can also harm orca whale populations, according to another WWF-funded study. The researchers were particularly concerned about marine mammals in the Arctic, such as Arctic seals, which are already vulnerable to climate impacts including reduced ice cover which normally offers protection. Human-caused underwater noise can cause seal populations to stop feeding forays earlier than normal and become easier targets for predators. Some efforts have been made to mitigate the issue. In March, the Port of Seattle announced it would invest in technologies to minimise underwater noise for its marine life, which includes the endangered Southern Resident killer whales. For instance, a pilot implemented a double wall piling system which is designed to cut noise travelling in water. Elsewhere, collaboration between the General Fisheries Commission for the Mediterranean and OceanCare is aiming to address noise pollution among other threats to marine species. Small measures to alter ship design can help – regular propeller maintenance and polishing can curb cavitation bubbles which generate noise. Slowing down the speed at which vessels travel can also minimise noise by up to 50% if speeds are reduced by 10% to 20%.
The University of St Andrew’s study’s authors also add that firms must scale up efforts to document information such as where and when their vessels generate underwater noise. Records such as this could better inform authorities monitoring the ocean on how they can reduce noises or plan mitigation strategies to curb the impact on marine species.