On 7 May 1942 a World War II naval battle was unfolding in the heart of the Coral Sea a few hundred kilometres off the North Queensland coast. At 0720 hours Japanese scouts spotted the American oil tanker USS Neosho and its destroyer escort USS Sims en route to refuel US navy ships. Mistaking the tanker for an aircraft carrier, the Japanese command dispatched torpedo bombers against the American vessels. By morning’s end, both ships and many of their crew had been claimed by the sea.
It’s not known how much oil the Neosho contained when it was torpedoed during the Battle of the Coral Sea – or how much remains stored inside this shipwreck 83 years later. All of Neosho’s oil may have spilled into the ocean when it was bombed in the 1940s. But there’s a chance the shipwreck still holds significant quantities inside fuel tanks that are slowly but surely corroding in the ocean’s salty waters.
The Neosho is one of thousands of WWII shipwrecks scattered across earth’s oceans. These mostly steel or iron hulks have sat in a salty, corrosive environment for more than 80 years and are now deteriorating: some leaking globules of oil into the marine ecosystems; others on the verge of collapse, threatening to release multiple tanks’ worth of bunker fuel. The condition of each WWII shipwreck and the pollution risks they pose vary – but collectively, they’re known as ‘potentially polluting wrecks’ (PPWs).
An IUCN report published in April 2023 identified more than 8500 PPWs across the globe, mostly from WWII, and estimated that these hold 6 billion gallons of heavy fuel oil (22.7 billion litres) – more than 30 times the amount released in the 2010 Deepwater Horizon disaster, the largest marine oil spill in history.
As well as oil, some PPWs have unexploded munitions and chemical weapons that contain heavy metals. The long-term effects these pollutants could have on ocean chemistry and marine life is not yet fully understood.
“It will get to a point where whatever oil was left in them, it will be released,” says Dr Matt Carter, maritime archaeologist and research director for the Major Projects Foundation, a not-for-profit based in Newcastle in New South Wales that’s working to decontaminate high-risk PPWs throughout the Pacific.
“The big concern is that these wrecks have been underwater for so long that they’ll get to the point where they collapse, they simply don’t have the [structural] strength anymore… But the multimillion-dollar question is, how much oil is there?”
Aside from corrosion, there are several things that might affect a WWII shipwreck’s structural integrity, such as its depth and orientation on the seabed.
“It’s a case-by-case basis, so it really depends on how the ship was sunk,” Matt explains. “Did it sink slowly and intact, or did it get blown into pieces? Is it upright, or is it lying on its side?”
The latter is more prone to collapse compared to an upright wreck, because its structural supports weren’t designed to bear the weight on its sides. Matt says these rusting supports can suddenly give way, causing the ship to flatten like a pancake and release its oil all at once.
Shipwrecks in shallow waters are usually less stable than deep-water wrecks, because they are more likely to be disturbed by boats and divers, impacted by storms, and knocked about by waves and currents.
“The conventional thinking is that the deeper the shipwrecks are, the more stable they are,” Matt says. “But even so, we know these wrecks are corroding over time, and we do have evidence from overseas that even deep wrecks release oil. We have some slicks coming up from wrecks in the Solomon Islands that are over 1000m deep.”
Preventing pollution
The good news is that decontaminating a PPW is a reasonably straightforward task. It typically involves a group of scuba divers descending to the shipwreck site, drilling holes into its tanks and pumping out the oil, then returning to the surface to dispose of it.
“It’s pretty surgical,” Matt says. “You keep the wrecks as intact as possible.”
This type of prevention is also a fraction of the cost of cleaning up an oil spill after a shipwreck collapse, which the Major Projects Foundation estimates to be 10 to 20 times more expensive.
Decontaminating shipwreck sites is being done routinely in places such as the US and in the Baltic. Australia hasn’t yet carried out these preventive measures – but has the right experts, tools and technology to respond to an oil leak quickly and efficiently should the need arise.
“Australia has quite good oil spill response capability,” Matt says. “We know these wrecks are on our doorstep here in Australia, but we do have some response capability, which makes them a lower risk overall.”
The same can’t be said for Australia’s neighbours in the Pacific. “When we go to the Solomon Islands or Micronesia, they just don’t have any [oil response] capability,” Matt says. “[They’re in] a vulnerable position in terms of oil spills – that’s where we focus our attention.”
The Major Projects Foundation has partnered with the Secretariat of the Pacific Regional Environment Programme to help build the oil-response capability of Pacific Island communities across Samoa, the Federated States of Micronesia, Fiji, the Republic of the Marshall Islands, Solomon Islands and Vanuatu.
“We work collaboratively with the people in these countries, [where] the problem is in their backyard,” Matt says. “They didn’t cause the problem, but they’re the ones having to face the impacts now.”
Of the 8500 PPWs identified in the IUCN report, an estimated 3800 lie in the Pacific. Of these, Matt and his team have identified 60 high-priority wrecks that need urgent attention, about a third of which lie inside Chuuk Lagoon (formerly Truk) in the Federated States of Micronesia.
“In Chuuk, you get these wrecks that have become artificial reefs and just absolutely covered in fish life, and they’re still full of thousands of litres of oil,” Matt says.
“The wrecks in Chuuk are amazing historic archaeological sites, and yet they are this pollution threat. They’re also tourism assets and war graves, so we’re very careful around how we deal with the shipwrecks. It might be easier to remove the entire wrecks, but that’s not something we’d look to do because they are cultural sites and the rest of it.”
The Major Projects Foundation received funding from the Australian Government through its foreign-aid budget to visit the Chuuk Lagoon and help local authorities deal with the issue. The project is also building local capacity for the Chuukese to assess and remediate high-risk sites in the future.
“Chuuk Lagoon has been our big project over the last few years,” Matt says. “We went diving on the wrecks and mapped them, surveyed them, to understand what condition they’re in and get a better idea of how much fuel could still be on them.”
This data also allowed Matt and his team to do oil-spill modelling, which identified where the oil would travel if a large amount was suddenly released.
WWII shipwrecks in Australian waters
Six of the 60 high-priority shipwrecks identified by the Major Projects Foundation lie in Australian waters. Three are American naval ships – the Neosho, the Sims and the USS Lexington – inside Queensland’s Coral Sea Marine Park. Two lie in Victoria’s southern waters: the US merchant ship MV City of Rayville, inside Apollo Marine Park near Cape Otway; and the SS Cambridge, a British merchant vessel inside Beagle Marine Park in the Bass Strait. Both sank after striking German mines in November 1940.
The sixth is the MV Limerick, a New Zealand-registered British cargo vessel that lies about 18km off the coast of Ballina and Cape Byron in northern NSW. On 26 April 1943 the 8724-tonne steamship was travelling in a convoy from Sydney to Brisbane when a Japanese torpedo struck its port side. Seventy of its 72 crew survived.
Multibeam imaging of the shipwreck by CSIRO in 2012 revealed the 140m-long shipwreck rests upside down on the seabed. That’s a good thing in terms of its structural stability, but slightly disappointing for maritime archaeologists looking to study the wreck.
“It’s completely inverted, which is a real shame because all the interesting stuff is on the top,” says Dr Brad Duncan, senior maritime archaeologist with Heritage NSW.
Heritage NSW, part of the Department of Climate Change, Energy, the Environment and Water, is the government body tasked with identifying, managing and protecting NSW shipwreck sites on behalf of the Commonwealth Government.
The Limerick is the only WWII shipwreck in NSW that’s known to leak oil. “It’s not a common problem that we’ve got up and down the coast,” Brad says. “The Limerick is the only one in the state where we’ve ever had that issue.”
Despite this oil leak, the Limerick’s structural stability, depth (about 90–100m) and offshore location means it doesn’t pose much of an environmental risk compared to other wrecks in the Pacific. Naval warships carried significant quantities of fuel that allowed them to cross vast expanses of ocean.
The Limerick, on the other hand, was a merchant vessel sailing from Sydney to Brisbane; it probably held enough fuel to only cover that stretch of the coastline. Brad says most of this fuel would’ve been released in the immediate aftermath of the torpedo strike. “The size of the charge that exploded the vessel is more than likely to have ruptured most of the oil tanks at the time,” he says.
Tim Smith OAM, maritime archaeologist and director of assessments at Heritage NSW, agrees that the environmental risk posed by the Limerick isn’t cause for major concern. “It’s a moderate risk in NSW waters,” he says. “I think it’s hard to say if one of our wrecks [will] fall apart in the next 50 years and create a polluting event. Because of where they are in Australia – in the coastal waters – it’s less of a marine environmental risk, because they’re usually offshore, outside of coastal zones. But it’s an aspect of the management of wartime ships that Heritage NSW is acutely aware of and is monitoring.”
When the Limerick’s oil leak was first discovered, Heritage NSW monitored the site over a period of about three months. “We collected samples of the oil on the surface and sent it to laboratories and had it analysed,” Tim says.
The lab report revealed the oil was bunker fuel and lubricating oil. “That indicated that one of the fuel tanks on the wreck had failed because of corrosion, and that [oil] had been seeping out. Often it’s not a catastrophic thing; it’s small globules of fuel oil going up to the surface, and it expands on the surface and dissipates,” Tim says.
“These big ships had up to 10 major fuel tanks on board, so this is probably a minor one that had failed, because it did effectively bleed out and the risk dissipated. But it’s something we manage as a managing authority, because it’s a bigger story in the Pacific.”
Who should pay?
In the Federated States of Micronesia, the issue of polluting WWII shipwrecks is not a hypothetical worry but a reality. In WWII, Chuuk Lagoon was a vital Japanese naval base that housed more than 37,000 Japanese people. Today, more than 50 Japanese shipwrecks lie submerged in its waters, along with dozens of aircraft, submarines and tanks.
The sheer number of shipwrecks in Chuuk has made it one of the world’s best-known scuba-diving sites, attracting thousands of tourists each year. But the economic future of this region is beginning to look uncertain as oil released from rusting shipwrecks washes up on beaches and pollutes local fish stocks.
Dr Bill Jeffery is an Australian maritime archaeologist at the University of Guam who has spent decades working in Chuuk Lagoon. Over the course of his career, he has witnessed the deteriorating condition of the lagoon’s shipwrecks. “They’re starting to collapse and deteriorate significantly now,” he says. “Over the years, they’ve been leaking oil gradually. As these sites start to collapse more and more, oil will potentially come out in volumes.”
Bill explains that ‘cathodic protection’ can slow down corrosion on shipwrecks. Cathodic protection involves one of two methods: either applying a controlled electrical current to prevent corrosion; or using ‘sacrificial anodes’ such as zinc or aluminium, which can act like a shield that corrodes instead of the ship’s iron. But applying cathodic protection to all the submerged shipwrecks in Chuuk is not financially feasible. “These are big ships – 10,000-tonne. Not as big as present-day ships, but in Chuuk there are 50 of them,” Bill says. “It’s a big, big, big task, and it just won’t happen. Maybe we’ll save one or two of them. But, you know, you’re looking at hundreds of millions of dollars.”
The question of who is responsible for cleaning up these oil spills – and who should foot the bill – is a contentious one. The US has removed oil from some of their PPWs across the Pacific. Japan has too, but not at scale. “The Japanese have been doing stuff over the last 10 years, but it’s very piecemeal, very labour-intensive,” Bill says.
The rest is ultimately left to the Pacific communities. “They [were] innocent bystanders in someone else’s war…and now they’re the ones sitting there with all the oil impacting their environment,” Bill says. “It’s not their responsibility at all.”
These rusting warships have sovereign immunity, which means they remain the property of the state that owned them at the time of sinking. Legally speaking, the Japanese wrecks in Chuuk Lagoon belong to Japan, not the Federated States of Micronesia, so they cannot be removed from the water or salvaged for parts. Their status as maritime graves makes the issue more politically sensitive.
“The countries [US and Japan] say it’s their shipwrecks, their material remains, their cargo,” Bill says. “I guess it’s ironic because if they found valuable cargo, they’d be jumping up and down about wanting to take it, protect it. But when it’s the oil coming out, no one really wants to do anything with it.”
That means it’s up to Pacific researchers to come up with innovative solutions to the problem.
Dr Awei Bainivalu is a Fijian scientist who recently completed her PhD in environmental bioremediation at the University of Newcastle. Her PhD investigated whether naturally occurring bacteria or microbes could be deployed onto leaking WWII shipwrecks to ‘eat’ the toxic oil and convert it into less harmful compounds such as carbon dioxide.
Using oil samples collected by the Major Projects Foundation, Awei analysed the toxic compounds – specifically targeting mono-aromatic hydrocarbons and poly-aromatic hydrocarbons – present in the oil, and also investigated if any naturally occurring bacteria were present in the oil.
“I worked on growing the hydrocarbon-degrading bacteria in the lab,” Awei says. “I isolated and cultivated a group of bacteria that could be reintroduced into the oil. Then, I experimented with modifying this bacterial consortium and monitored how effectively they could degrade the toxic components over time.”
Like most scientific research, Awei emphasises that this isn’t a one-size-fits-all solution. “As much as we’d want that to happen that way – you get a superbug, throw it in the sea, and it fixes the problem – it’s not that simple,” she says. “Each shipwreck is unique, with its own oil fingerprint and associated bacteria. The bacteria I work with may or may not work in other wrecks.”
Awei’s research was a pilot study she hopes will be the starting point for a larger body of research into novel ways of dealing with marine oil pollution in the future. “Most of these wrecks are in areas with high biodiversity,” she says.
“The oil spills from these wrecks threaten the coral reefs, which are important breeding grounds. We depend on these marine ecosystems. They’re our lifeline. It’s crucial that we address this issue. We need to be aware, but unfortunately, many are not.”