Australian scientists have, for the first time, determined the cause of mysterious skin lesions found in a rare species of endangered bottlenose dolphins in Victoria’s east

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Australian scientists have, for the first time, determined the cause of mysterious skin lesions found in a rare species of endangered bottlenose dolphins in Victoria’s east.

Key points:

  • Australian scientists for the first time have determined climate change as the cause of deadly skin lesions found in two species of extremely endangered bottlenose dolphins in Australia.
  • Researchers have, for the first time, identified and defined the condition, which they have called ‘Fresh Water Skin Disease (FWSD)
  • With dolphin numbers on the decline, experts are worried for the future of Burrunan dolphin in eastern Victoria

Since September, six dead Burrunan dolphins have been reported in the Gippsland Lakes and all of them showed similar discoloured ulcers on the skin’s surface.

Finally after decades of research, Australian marine animal experts have been able to fully characterise the lesions and come up with a name for the condition — Fresh Water Skin Disease (FWSD).

So what is it?

Equivalent to human ‘third degree burns’

Fresh Water Skin Disease occurs when there is a sudden increase of fresh water in a usually salty water system.

It then causes skin lesions on marine dolphins that can only survive in saltwater conditions.

The head of a dead dolphin with severe skin lesions.

The severity of the lesions have been likened to third degree burns in humans.(Supplied: Dr Nahiid Stephens)

Over time, the Gippsland Lakes have become more saline, due to a range of factors including years of drought.

Lead Researcher and Lecturer in Veterinary Pathology at Murdoch University, Nahiid Stephens said dolphins usually presented with the disease after heavy rain or a major storm.

“The Gippsland Lakes is a brackish to marine environment because it’s open to the sea so although its source is a river, because of marine water mixing its actually quite salty,” Dr Stephens said.

“The breaks in the skin cause the dolphin to lose vital ions and proteins from their bodies … so when all of that is oozing out of them, the fresh water then rushes in which causes swellings and ulcers.

“It kills them because it causes electrolyte disruptions in their [the dolphins] blood stream and they ultimately end up with organ failure.”

Due to breaks in the skin, the animals can also develop secondary injuries including algal, bacterial and fungal infections which are usually catastrophic to their already weakened immune systems.

Climate change will ‘increase disease’

With just 60 Burrunan dolphins left in the Gippsland Lakes and another 120 individuals at Port Phillip Bay, experts are concerned for their future.

But Dr Stephens said FWSD was not just unique to the Burrunan species, the lesions have also been discovered in the small bottlenose dolphin population at Swan-Canning Riverpark in Perth as well as several other locations around the world including along the Gulf of Mexico.

Dead bottle nose dolphin washed up on shore.

Researchers also found FWSD in bottlenose dolphins at Perth’s Swan-Canning Riverpark in Western Australia.(Supplied: Dr Simon Allen, University of Western Australia)

“These creatures live in estuarine and coastal areas in urban environments and FWSD is just one stressor that they face,” she said.

Common to all FWSD discoveries globally, is a preceding extreme weather event like that seen in the United States after Hurricane Katrina in 2005 and Hurricane Harvey in 2017.

“What we know from comparing to similar situations across the world, is that these outbreaks always occur after sudden heavy rainfall, which makes us very concerned that we’re going to see an increase of FWSD in dolphins that live in low-lying areas and are vulnerable to worsening climate change,” she said.

“If they’re pushed to the brink we may lose them and they’ll completely die out.

“We have to tackle the wicked problem of climate change which is multi-faceted and we also have to alleviate other threats to dolphins, because how many more wakeup calls do we need before it’s too late?”

Increased monitoring

Founding Director of the Marine Mammal Foundation, Kate Robb has been working with dolphins for more than 16 years.

Her extensive research led to the formal description and naming of the Burrunan dolphin, which means a ‘large sea fish of the porpoise kind’ in the Boonwurrung, Woiwurrung and Taungurung languages.

Pod of dolphins swim in lake

Monitoring of the Burrunan dolphins has ramped up in Gippsland to find out if contaminants from bushfires also contribute to the deadly lesions.(Supplied: Marine Mammal Foundation)

Dr Robb said 80 per cent of dolphins in the Gippsland Lakes had presented with skin lesions — and sediments from bushfire run-off could also be a contributing factor.

“We will continue to monitor the dolphins, take samples for pathology and investigate the causes, but we need help from the public so we can see how many dolphins are showing symptoms, how many more are dying and do as much testing as possible,” she said.

Locals from around the lakes have been urged to report dead or sick-looking dolphins to the Whale and Dolphin Emergency Hotline on 1300 136 017 along with the locations, date, time and number of animals.

“Don’t go too close or touch the animal, whether it’s alive or dead as you could compromise our sampling and testing,” Dr Robb said.

People have also been warned to stay at least 100 metres away from dolphins if in a vessel, and at least 300 metres if on a jet ski.

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