A 200,000-litre diesel leak into the Tafitoala reef, off Samoa, raises concerns about long-term ecological risks from toxic chemicals, despite Royal New Zealand Navy assurances.
After hitting the reef it was surveying last week, HMNZS Manawanui caught fire, capsized and released diesel into a 5000 square metre region, which is home to vast quantities of marine life.
University of Otago marine science lecturer Dr Bridie Allan told Te Ao Māori News that, if this had happened in New Zealand’s exclusive economic zone, people would be responding in a “very negative” way.
Samoa’s Maritime Pollution Advisory Committee released the estimate of 200,000 litres but, in an interview by Q+A, Defence Minister Judith Collins said she didn’t see how it could be correct based on one video by the Defence Force that showed “a little trickle”.
When asked why Samoa‘s explanation was different, Collins said she didn’t know but understood people got worried in these circumstances and people were being cautious.
Former Samoan PM Tuia Pu‘a Leota told RNZ Pacific that Collins’ statement was “unkind and careless” and that it was not a trickle but a disaster.
The Navy‘s deputy chief Commodore Andrew Brown has said the diesel spill was a small amount which undergoes a “natural evaporation process” and “waves and general tides dissipate that”.
But, in an interview with Pacific Media Network, Allan said while it appeared the surface oils were dissipating, it did not reduce the risk of contamination.
“As oil is agitated at the surface due to wave and wind energy, the chemical components, including highly toxic heavy metals and polyaromatic hydrocarbons (PAHs) in the oil are weathered out.”
This results in chemicals dissolving into seawater, which can expose marine organisms.
“These chemicals can be quite toxic even at low doses, increasing mortality rates,” Allan said.
She told PMN very small doses had been demonstrated across a range of scientific studies to cause a range of physiological effects such as cardiac, spinal and craniofacial deformities in marine organisms as well as behavioural impairments following exposure to low levels of PAHs.
“The effects of a catastrophic oil spill can persist over a long period as the chemical components of oil are absorbed by marine organisms and deposited in marine sediments,” she said.
University of Waikato science associate professor Nick Ling told RNZ the 5000 square metres was a “small footprint” and said the ship could create a new habitat for marine creatures.
Allan said the magnitude of the affected site was difficult to interpret without information on the overall reef size.
“If the total reef is 50,000 square metres, then that is 10% of the reef being affected,” she said.
“Yes, the ship could create new habitat but not all habitats are good quality.”
She said artificial habitats could create ecological traps and it could affect their overall fitness if it isn’t a good quality habitat.
“For example, old tyres used to be used to create marine habitat but it turns out they release toxins and microplastics and affect the fitness of marine fish.”
Ling told RNZ the ship would eventually break down and it was hard to say whether it would be a good habitat.
Allan agreed: “We have no idea about this. Given it takes a long time to decommission a boat, with all potential toxins removed, it seems unlikely that the presence of this ship won’t negatively affect the environment.”