Dolphin enthusiasts are mourning the slow death of a unique pod known worldwide for their tricks and aerial flips, with fears an unknown toxicant in the waters of Port Adelaide is killing them off.
Adelaide beachgoers were enthralled last October when a dolphin, trapped in a river outlet, spent the afternoon tail-walking until returning to sea when the tide came back in.
It's an act passed down among Adelaide's dolphins for generations, starting in 1988 when Billie, a female trapped in a polluted marina, spent two weeks recuperating in a former dolphinarium learning the tricks of trained mammals before returning to the wild.
But in the nearby Port Adelaide River, where many of these tail-walking dolphins live, a mysterious condition is killing them.
Five males have died after turning abnormally thin and, with investigating authorities so far stumped as to what's behind their illness, a passionate community of followers is worried a pod is on the verge of being lost altogether — along with its famous display of "animal culture".
The sanctuary
The Port Adelaide River estuary and adjacent Barker Inlet form part of the Adelaide Dolphin Sanctuary (ADS), a 118-square-kilometre body of water that stretches north into the Gulf of Saint Vincent and the Adelaide Bird Sanctuary.
Cargo ships that enter at Outer Harbor are greeted on one side by a mangrove-lined shore, a sparsely populated peninsula of dirt on the other, and probably several dolphins leaping from their bow wave.
As they make the way towards South Australia's busiest shipping port, the dirt gives way to high fences and Australia's naval shipbuilding headquarters.
Then comes an array of factories, warehouses and industry clustering the shores, including Adelaide's main gas-driven power station and its accompanying signs warning about elevated water temperatures.
Jenni Wyrsta is a daily visitor to the area. She drives nearly an hour from the Adelaide Hills to arrive at first light with her telephoto camera to capture images for the Port River Dolphin Watch (PRDW) Facebook page she launched in 2013.
Back then, she says members would cruise out to the gulf on the Dolphin Explorer and spot nearly 40 dolphins, before returning to the Port River and its inlets to see another 12 dolphins "playing, feeding, splashing, just having a ball".
"Today you're lucky if you might see one or two in the river, because we only have about six left in the Angas Inlet — the numbers have fallen dramatically," she says.
It is these dolphins — those that reside in the Angas Inlet and North Arm sections that branch off from the river to form Torrens and Garden islands — that are of greatest concern.
A personable pod
While upwards of 300 transient dolphins come and go from the gulf, there are about 30 resident bottlenose dolphins across the estuary, some of which overlap in their home ranges which include a conservation park and aquatic reserve.
They are a major drawcard for tours from Port Adelaide and kayakers seeking close encounters while investigating the so-called graveyards of retired ships sunk into the mangrove sludge.
Enthusiasts have given the dolphins names like Mouse, Crystal, Mel, Bubbles, Hope and Gem, using the dorsal fins to tell them apart.
Jenni has not seen Gem since September.
She fears Gem has gone the way of Doc and Twinkle — two young, tail-walking males who disappeared in the middle of last year after showing signs of heavy emaciation.
Others, like Talulla and Squeak, turned up dead during the latter half of 2021, as did an unnamed dolphin near Semaphore Beach; Squeak's six-year-old brother, Hunter, was euthanased by authorities in October due to ill health.
The dolphins had several things in common: they were young males, they stayed close to home, they showed signs of emaciation.
Necropsies revealed shrunken lymphoid organs and secondary bacterial infections that did not usually affect dolphins — that is, their immune systems were heavily suppressed.
Jenni says 23 calves have also died since 2017, further threatening the population's future.
Compounding the issue has been the discovery of about 12 carcasses across Gulf of St Vincent beaches during March.
While it's the biggest mortality spike since 2013, these dolphins are believed to have died of different causes to those in the Port River.
A 'frustrating' mystery
An investigation launched in August by the state government involving experts from Adelaide and Flinders universities along with SA Museum has failed to find a primary cause for their immunosuppression.
Lucy Woolford, an associate professor in veterinary pathology at the University of Adelaide, is among those who have screened unsuccessfully for viruses.
"It's frustrating for us because there's nothing that's saying, 'Yes, it's an outbreak of this disease that's causing it'," she says.
"It's death by a thousand cuts."
Viruses have long been a factor in Gulf of St Vincent dolphin deaths.
In 2013 and 2014, morbillivirus was found to have caused immunosuppression and contributed to the death of more than 30 dolphins found on Adelaide beaches and the Yorke Peninsula.
But SA Museum honorary researcher Ikuko Tomo, who's been studying the cause of dolphin deaths since 2005, says the past five years have shown a distinct absence of any infection "significant enough" to have caused the deaths.
A sample tissue taken from Doc before he disappeared showed he had been exposed to brucella, a zoonotic bacterium that can cause dolphin abortions and male infertility.
Researchers, however, believe further surveillance is required to determine its wider role in calf deaths.
Morbillivirus is being investigated for its role in last month's mortality spike recorded outside the dolphin sanctuary.
Dr Woolford says about 12 bottlenose and common dolphin carcasses were found from Henley Beach to Seaford and Maslin beaches south of Adelaide, Petrel Cove near Victor Harbor, and across the gulf on Yorke Peninsula.
Another dolphin, named Namor, was found dead in Port Adelaide's inner harbour, but Dr Woolford is keen to point out these deaths are very different to those recorded in the sanctuary last year.
"These new animals were in good body condition," she says.
"Namor was seen to be healthy and in good condition only a couple of days before he died."
She says the deaths in 2013 followed a morbillivirus outbreak in Western Australia; a recent outbreak in WA led the investigating team to "hypothesise" it's happening again.
"But the test results so far don't support that," Dr Woolford says.
She says further testing is underway and they're about to investigate whether a harmful algal bloom has caused the gulf die-off.
A history of violence
Closer to Port Adelaide and its bridges busy with cars and trucks, newly built apartments and terrace housing rise over the water.
Their modern pastel colours and murals betray efforts by successive governments to gentrify a working-class area with pockets of socio-economic disadvantage.
It's an area where industrial shipping (about 2,000 movements a year), conservation, boating and tourism have managed to co-exist for nearly two centuries — but it's not always been successful, and it has not been peaceful.
Squeak, whose body was heavily emaciated, also showed signs of severe blunt trauma on one side of his head and neck, suggesting he may have been hit by a boat while ill with a chronic condition.
Boat strikes are a constant risk for the dolphins; four calves killed by boats in 2018 prompted the expansion of speed limits across the dolphin sanctuary.
The sanctuary itself was legislated in 2005 to protect the estuary's dolphins and habitat following a spate of cruel incidents in which the animals were shot, speared and stabbed.
Tensions rise
As the fatalities grew last year, so too did the finger-pointing among the Port River's communities and dolphins followers.
Some refer to Jenni Wyrsta as "the hunter" because of her camera.
As well as marine life, she photographs fishers using heavy tackle in the port (a practice that has resulted in dolphin injuries) and other people like jet-ski riders acting dangerously around dolphins.
Last year Jenni changed the Port River Dolphin Watch Facebook page to a private group due to online antagonism from people she said were fishers.
She doesn't have an issue with fishers who use regular lines because the dolphins can snap them — it's just a "minority group" that she says poses a problem.
"I never aim my camera at fishermen, I crop out the people; I'm just after the heavy fishing gear, because there needs to be some new controls put in place."
An easy target
RecFish SA director Alex Williams says when the dolphins started dying last year, recreational fishers became an "easy target" for the "blame game".
He points out that fishers, for the most part, have very little interest or interaction with dolphins and generally try to avoid them altogether.
Any back and forth between a minority group and dolphin advocates exists on social media alone and not in the real world, he says.
"But if there is any issue with dolphins interacting more with fishers, then I think we need to look a little bit further up the chain as to why that's happening and the fact there's been some encouragement for dolphins to interact with humans in the area."
Line entanglements
According to the National Parks and Wildlife Service (NPWS), authorities intervene about once a year in the area to free a dolphin from fishing line entanglements.
Doc was one of these just weeks before the emaciated young mammal disappeared.
Jenni Wyrsta and her members have been lobbying authorities to intervene with the sick dolphins and give them medical treatment — or allow other groups like the locally based Australian Marine Wildlife Research and Rescue Organisation to do so.
The NPWS subsequently found itself under fire for doing a biopsy before cutting Doc loose, rather than use the opportunity to administer a course of antibiotics.
But NPWS marine parks regional coordinator Jon Emmett says the department's minimal-intervention policy is aligned with the way wildlife management agencies work worldwide.
He says dolphins are wild animals that are not used to being "handled or captured by people".
"It's an extremely stressful experience when we do have to capture them and perhaps disentangle them from fishing line or something like that.
"If it's a natural occurrence, then we try and allow nature to take its course."
He says he appreciates people's passionate views, suggesting it is probably the most observed dolphin pod in Australia because they live in an urban area and are so visible.
"We've got this challenge of balancing conservation with high levels of recreational use and industrial use, and there is a lot of industry in this area which was focused here in the early days of Adelaide's settlement."
Ideologies about intervention also differ among different groups of dolphin followers, sometimes putting them at odds with each other.
Three decades of study
Integral to the Adelaide Dolphin Sanctuary's foundation was dolphin expert Mike Bossley, who is affiliated with another group of followers — Dolphin Dock — and who lobbied for the ADS from the mid-1990s.
His curiosity was piqued 35 years ago when he read in a local newspaper about a dolphin that would swim alongside racehorses being exercised in the water off West Beach.
That dolphin turned out to be Billie, the playful critter that brought tail-walking back to the pod so that "eventually we saw seven or eight dolphins also tail-walking here".
"It was quite spectacular and is an example of what's known as culture in animal behaviour," Dr Bossley says.
He says dolphin numbers rose after the ADS was introduced until about 2017 when fewer calves were surviving, and then last year's death of males aged three to 20 "when they should be living into their 30s".
"We haven't had a spate of unexplained deaths involving young dolphins before.
"That doesn't seem to fit any pattern and implies there's been some recent toxicological event that's impacting these guys."
The search for a toxicant
In 2000, an Environmental Protection Authority (EPA) monitoring program found the estuary's water quality to be poor to moderate.
Heavy metals such as zinc, aluminium, cadmium, iron, lead and mercury were detected at five sites and attributed to industry, cars and urban run-off.
There was enterococci and streptococci bacteria at six sites — attributed to faecal matter in stormwater, septic tank seepage, boats and sewage outfalls — while chlorophyll across the estuary indicated the presence of algae.
The program named the former Penrice Soda Products factory, which had permission to discharge oxidising nitrogen and ammonia into the estuary, as a root cause for higher nutrients, along with the former Port Adelaide wastewater treatment plant.
In 2008 it said both had possibly assisted in the expansion of longer-lasting invasive algae species.
The hill behind the Garden Island boat ramp, where a car park has been adopted as the local burnout arena, is a former dumping site remediated in 2005 to mitigate fugitive gas emissions.
And in 2019 Flinders Ports received permission to dredge the shipping channel for the second time this century, removing 1.5 million cubic metres of material from waters off Outer Harbor and dumping it 30 kilometres away in the gulf.
Some fear the activity stirred up historic heavy metals and pollutants known to exist in the sediment.
Leading the government investigation is Department of Environment and Water's (DEW) conservation and wildlife director Lisien Loan, who says she's never seen dolphins deteriorate so quickly.
"We're not sure whether some of those longer-term pollutants are having an effect on the immune system overall, so we will be looking into those because there's definitely some pollutants and heavy metals that remain in the sediments," she says.
"This is why we're tapping into a whole range of experts … people who can provide input to us to try and narrow down what it could be, from disease, toxic things in the environment, a whole range of factors."
DEW commissioned independent analysis of Hunter, Talulla and the Semaphore dolphin which found "contaminants of emerging concern", such as phthalates, short-chain paraffin and pesticides, were "below detection limits" in the livers of the two ADS dolphins.
Trace metals and some persistent organic contaminants were detected at low concentrations, but they are considered similar or lower than what has been recorded in Gulf of St Vincent dolphins in the past.
Researchers believe it is unclear if the contaminants are having an impact on the ADS dolphins at such concentrations, but further monitoring will assess contaminant levels in their food supply, such as fish and invertebrates.
High lead levels
SA Museum senior mammal researcher Cath Kemper says heavy metals tend to have a longer-term influence on dolphins.
Dr Kemper says the dead Port River dolphins showed a "quick reaction" and she will therefore be surprised if dredging by Flinders Ports is a factor because it took place two years ago.
"I'm not excluding anything, but I'm just trying to keep our minds open and not necessarily grab onto things that might be a bit sensational and therefore not look at the big picture."
Dolphins in Adelaide's metropolitan waters, particularly the longer-living bottlenose species, are known to have accumulated higher lead concentrations than usual, which has been attributed to urban run-off and the use of leaded petrol.
"Maybe there's something else that has happened that's triggered or sort of reacted with the heavy metals to create a response," Dr Kemper says.
Is there enough food?
Others believe a lack of food in the estuary may be the root cause, but Alex Williams from RecFish SA says it's hard to give a definitive assessment on fish stocks because different fishers have varying opinions.
"If you go back 10 to 15 years ago, there was a fantastic bream fishery in the Port River and surrounding areas, but now you can barely find a legal bream and we don't know why that is," he says.
"But on the flip side of that, you're having more of the larger species, like your mulloway and yellowtail kingfish, coming in there and even snapper as well from time to time."
Some believe a disastrous die-off of mangroves adjacent the Barker Inlet at St Kilda from late 2020 — caused by the leaking of hypersaline water by Buckland Park salt mining — may have affected the food chain.
Environmental consultant Peri Coleman says the pollution will have "pickled" the mud crabs along the affected coastline, meaning they won't produce larvae for the small fish that typically enter the flats at high tide to eat and "double their weight in one night".
Those small fish are prey for bigger fish, which are in turn prey for even bigger fish, until they become food for dolphins.
"It's a food chain and the amount of zoea (larvae) you need to produce some kilos of fish, ultimately for a dolphin, is unfathomable," she says.
But Jon Emmett from the NPWS points out the estuary is still well-populated by the birds that rely on fish as well, and there is "still plenty of healthy dolphins in this area".
"It's also the case that some of the dolphins that have recently deceased have been found with food in their stomachs as well."
In Hunter's stomach were prawns — an endemic species that's not a regular part of a sanctuary dolphin's typical diet.
Researchers believe he probably ate the prawns while foraging as he was sick and unable to catch fish.
The despair of not knowing
Cath Kemper says it's common for dolphins to die without a clear explanation unless it is due to human interaction such as boat strikes or malice.
"The diseased ones are trickier, and part of the reason for that is we, as scientists around the world, don't have a lot of information on dolphin disease, so therefore it's harder to put all these things we find into a bit of context."
What is obvious, however, is the passion of Port Adelaide's dolphin watchers and their fears.
"People are going to be concerned and upset if [dolphins] are dying and there's no answers to it," Dr Kemper says.
"They've all got names, so that makes it closer to our heart, doesn't it?"
Mike Bossley says Squeak was "almost like a grandson" for him because he had followed Squeak's mother, and her mother before that.
"Until we can figure out exactly what the culprit or culprits are, there's not a lot we can do."
Jenni Wyrsta says Doc had been her favourite and she worries for Port Adelaide if the pod is lost.
"That would affect a lot of people, because there's a very big community of people following the dolphins' lives.
"If we lose dolphins, I'd be so devastated that there'd be no point coming down here anymore."
There is some cause for hope.
Several calves have recently been born, with Mouse giving birth to Piki — alternatively named Neon by Dolphin Watch — in February, and Rocket giving birth to Ripple.
It follows the birth of Saki — or Frankie — to Dinah late last year.
"Their body condition is very strong, they're developing very well, learning lots of new skills, so everybody's got their fingers crossed," Jenni says.
Credits
Reporting: Malcolm Sutton
Video & photography: Malcolm Sutton, Jenni Wyrsta, Marianna Boorman and David McMeekin
Producer: Daniel Franklin
