How ocean noise pollution is threatening Chinese white dolphins, affecting their ability to hunt, navigate and communicate

HONG KONG — Noise pollution is a common complaint among city dwellers in highly urbanised Hong Kong. But the problem runs deeper, affecting species in the ocean, including the vulnerable Chinese white dolphin.

To show just how damaging ocean noise pollution is, Hong Kong photographer and documentary maker Daphne Wong last month released the film Sea Of Noise in collaboration with conservation organisation WWF-Hong Kong.

“It’s easy to see the impact construction has on land but what’s less obvious is the bigger impact it’s having underwater,” Ms Wong, 25, says. “Sound travels quicker and further underwater, so I wanted to capture what the Chinese white dolphins are experiencing, the impact from their perspective.”

Ms Wong says sound is vital for cetaceans, who rely on it to help them navigate, hunt for food and communicate through echolocation, a complex system of sound waves made up of “clicks and whistles”.

“But these signals are being interrupted by high-speed ferries and other marine vessels,” she says, adding the best way to describe the effect of underwater noise from marine traffic is that it muffles the dolphins’ own sounds.

Marine traffic is not the only man-made threat to the Chinese white dolphin. Major coastal reclamation for the Hong Kong International Airport, Hong Kong-Zhuhai-Macau Bridge and now the third airport runway has resulted in habitat loss, while water pollution and overfishing have also decimated the population.

Ms Wong’s 2018 documentary Breathing Room looked at how rapid urbanisation was taking a toll on Chinese white dolphins.

According to the Hong Kong Dolphin Conservation Society, population numbers plunged from 188 in 2003 to 32 in 2018, before rising slightly to 52 in 2019. Chinese white dolphins are listed as vulnerable on the Red List of Threatened Species — meaning they are threatened with extinction, according to the International Union for Conservation of Nature — and are a grade-one national key protected species in mainland China.

In Sea Of Noise — which screens on July 3 at The Eaton in Yau Ma Tei — Ms Wong blends underwater clips, animations and interviews to paint a 30-minute sensory picture of the challenges faced by Chinese white dolphins, while sending a message about the importance of preserving Hong Kong’s natural ecology.

Ms Wong has also woven into the film sounds from WWF hydrophones — underwater data-collecting devices that record cetacean sounds to help experts analyse species behaviour and numbers.

Most footage, she says, is above water, as the Pearl River Estuary, the dolphins’ main habitat, is not only “blackish murky water with poor visibility, but the conditions there for non-technical divers are dangerous”.

“People say ‘why don’t the dolphins just move to another area’ but they chose that spot for a reason, including it being a reliable food source,” she adds.

Ms Wong hopes the documentary not only raises awareness of the dolphins’ plight but also of the various campaigns to protect the species and its habitat, including one from WWF-HK that calls on the government to designate a dolphin conservation area in the waters off the western and southern coasts of Lantau Island by 2024.

Ocean noise pollution is a global issue, with the stranding of whales and dolphins the most disturbing consequence, Swiss non-profit OceanCare says. It also causes marine animals to flee habitats and can have a disruptive impact on mating, finding food and nursing the young, it says.

In 2018, using underwater microphones on the bottom of the Atlantic Ocean, researchers from the University of Maryland’s Centre for Environmental Science in the US found that dolphins are simplifying their signals so they can be heard over the noise from marine vessels.

Earlier this year, scientists at King Abdullah University in Saudi Arabia found that noise from shipping, construction, and sonar and seismic surveys were having a negative impact on the healthy ocean soundscape. SOUTH CHINA MORNING POST