The stricken HMNZS Manawanui with smoke coming from it. Photo / Profile Boats
The stricken HMNZS Manawanui with smoke coming from it. Photo / Profile Boats
A marine ecologist with experience in shipwrecks expects there could be significant damage to the reef struck by the HMNZS Manawanui
There are already concerns over spilled oil, with a Samoa Ports Authority tug boat deployed to help prevent further damage
Another marine scientist who surveyed the reef in the 1980s has described the accident as ‘devastating’
A sunken 5700-tonne Navy vessel poses serious environmental risks for the pristine reef it ran aground on off the coast of Samoa – but the damage might be reduced if it’s able to be fully removed, says a marine ecologist who’s dealt with major wrecks.
However, Defence Minister Judith Collins has this afternoon said the ship is “pretty much gone”, with little chance of salvage.
The 84.7m-long HMNZS Manawanui sank this morning after hitting a reef near Safata Harbour, off the southern coast of Upolu last night.
The Samoa Observer reported there were concerns regarding an oil spill, and that a Samoa Ports Authority tug boat had been sent to help prevent further damage.
A Kiwi who watched the catastrophe from the shore said the specialist dive and hydrographic vessel had sunk in a marine reserve, with water depths of more than 2km, and villagers were visibly upset.
It wasn’t immediately clear how much oil was on the $100m ship, which was surveying the reef near the village of Siumu when it ran aground, prompting the evacuation of its 75 crew and passengers.
The New Zealand Defence Force said it was working with authorities “to understand the implications and minimise the environmental impacts”.
Marine ecologist Phil Ross said tropical reefs like the one it hit were typically abundant with sea life and a rich diversity of corals.
“The reef is a long way offshore, so it’s likely as pristine a reef system as you can expect to see anywhere in the tropical Pacific.”
Ross expected the wreck would cause nearby corals to die, which had knock-on effects for the sea life that relied on it.
“The diversity of sea life is closely tied to these coral habitats. There’d be fish and invertebrates living within that coral matrix and those species will be very impacted.”
Ross said the biggest question looming over ecological fallout would be whether the Manawanui could be taken off the reef.
He said nearly all of the 184m-long Kea Trader was removed from New Caledonia’s Durand Reef after it grounded in 2017, and its ecosystems were able to recover.
Marine ecologist Phil Ross. Photo / Supplied
“The big question here is whether the ship is coming off, or staying on there and then breaking up and losing all its oil: I assume it was well stocked with fuel.”
Aside from the immediate risk of oil spill, Ross – who was involved with 2011′s Rena disaster off Tauranga and the 2019 grounding of the MV Solomon Trader in the Solomon Islands – said the most significant environment impacts would come from metals as they broke down over time.
“If the ship isn’t coming off that reef, then the long-term impact very much depends on what salvage activity happens.”
Unlike the challenges that salvors faced after the MV Rena wreck, he said there would at least be a detailed inventory of what cargo and potential pollutants were on the Manawanui.
Waikato University marine scientist Professor Chris Battershill, who was also closely involved in the response to the Rena grounding, said the Manawanui was “devastating”.
“There’s no winners in that. It’s just really sad.”
He believed the reef was the same one he’d surveyed for a study in the 1980s, and the data could potentially help establish a baseline to measure impacts from the grounding.
“We collected everything and identified everything that we came across: there’s massive diversity in and around there,” he said.
“It’s a typical tropical coral reef community – hard corals, soft corals, sponges and there’s also a really high diversity of fishes.”
Battershill also expected there’d be leakage of oil, hydraulic fluids and other pollutants.
But as the Rena experience showed, by the time the oils reached the shore, he said it was possible the most potent elements – called polycyclic aromatic hydrocarbons, or PAHs – may have already “weathered off” on the sea surface with wave and wind action.
“As for metals, there’ll be some sort of contamination from them immediately around the vicinity of the ship, but as we also found with Rena, they didn’t spread very far.”
Battershill said one metal of concern was tributyltin, or TBT – but if the Manawanui had contained any, it could be possibly contained at depth if the wreck site was deep enough.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
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