Moa Point sewage spill a potential ‘ecological catastrophe’
Thursday, 5 February 2026
A marine biologist says the Moa Point sewage spill has the potential to be a large ecological disaster that would take many years to reverse.
About 70 million litres of untreated sewage is pouring into Cook Strait every day following catastrophic flooding at Moa Point sewage treatment plant, with Wellington Water unable to say how long it would continue and the public warned to stay away.
Victoria University’s senior lecturer in marine biology, Dr Christopher Cornwall, said he was “very concerned” about the impacts for marine life, which included paua, kina, crayfish and various fin fish.
He said the worst case scenario involved denudation of the native kelp forest, which the marine life relied on as part of a rich ecosystem.
Read more:
Council knew sludge plant had 50% chance of cost blowout – bill to top $500m
Councillors demand review after Wellington sludge plant budget blow-out
Years of red flags before ‘catastrophic’ Wellington sewerage failure
Invasive kelp could spread to replace the native kelp and dominate the reef, smothering out organisms that lived on the rock faces, like pāua, sponges and ascidians/sea squirts, he said.
Pāua, he said, were especially sensitive to any changes in the environment, and lose their ability to grasp onto the reef when exposed to fresh water from the sewage, causing death.
He said it was hard to know what the extent of the damage would be as it depended on how quickly the sewage was able to be contained.
“The longer that stress is out there, the greater the chances that stress will accumulate and cause ecological harm,” he said.
“The quicker it’s resolved, the lesser the impacts will be of this event.”
He said the situation needed to be dealt with as soon as possible, describing the ecosystem as a “jewel in the crown of Wellington” and pointing to Taputeranga Marine Reserve.
Ohad Peleg, marine ecologist and post doctoral research fellow at Victoria University, said kelp was important to marine life in the same way that forests were to birds.
He stressed that there was no way of knowing what the outcome would be.
“The kelp could be actually be pretty happy with the extra nutrients, or it could not be, because these extra nutrients would mean cloudier water, less light penetrating the sea floor, and less light for the kelp to photosynthesise.”
Peleg and Cornwall are part of a team of scientists who have volunteered to monitor the effects of the wastewater spill, and will collect water samples and monitor marine life as soon as it was safe to enter the water.
“We have such a beautiful marine reserve here, it's one of the best reserves in the country I reckon and it would be devastating to see some adverse effects to the reefs in the marine reserve,” Peleg said.
Greater Wellington Regional Council environment senior advisor Penny Fairbrother said NIWA modelling, showing the harbour being largely immune from the outfall, was based on modelling showing a current was likely to drive the sewage to the west.
The preliminary results indicated fairly little contamination outside of the immediately affected area at Tarakena Bay, where there was obvious visible pollution and a strong odour.
Confirmed lab tests took about two days to be returned, she said.
When questioned if it knew of any environmental impacts, a Wellington Water spokesperson said it was closely monitoring the situation and undertaking water sampling.
The traditional Island Bay blessing of the boats on Sunday, a nod to the suburb's Italian history, was cancelled.