Juvenile sea urchins sampled from part of Kaikoura Canyon that were covered by mud from submarine landslides. Photo / NIWA
Juvenile sea urchins sampled from part of Kaikoura Canyon that were covered by mud from submarine landslides. Photo / NIWA
Ten months after the devastating magnitude 7.8 quake that wiped out marine life deep in the Kaikoura Canyon, scientists have happily discovered promising signs of recovery.
The huge canyon, running up to within 500m of the coast south of Kaikoura, has been recognised as one of the most productive deep-seaecosystems on Earth, attracting large marine mammals that have made the South Island town a tourist favourite.
When November's earthquake triggered submarine mudslides and sediment flows that devastated its abundant deep-sea life, many feared the worst.
But, within weeks, Kaikoura's famous whales returned - and now a team of NIWA scientists have returned from an expedition with seafloor samples and video footage to suggest the canyon's tiniest residents are bouncing back.
In July, NIWA surveyed the seafloor of the entire canyon area using a multibeam echosounder seafloor-mapping system on RV Tangaroa, which revealed modifications made to the seafloor by submarine landslides triggered by the earthquake.
The most recent voyage, completed on Sunday, was specifically designed to sample the seafloor that had been scoured or buried as a result of the submarine landslides, and begin to determine the potential recovery of the deep-sea ecosystem.
NIWA ecologist Dr Daniel Leduc said there was evidence that juveniles of animals that once dominated the head of the canyon have now begun colonising the seafloor.
A photograph of the seabed in Kaikoura Canyon showing a dense cluster of juvenile sea cucumbers - indicating that recovery of the deep-sea ecosystem is beginning to take place. Photo / NIWA
"The deep-sea communities might be recovering faster than we originally thought, with high densities of small organisms such as urchins and sea cucumbers in some areas of the canyon, as well as large numbers of rattail fishes swimming immediately above the seabed."
How the deep-sea Kaikoura Canyon would appear if it was exposed. Photo / Animation Research/Taylor Made
Voyage leader, geologist Dr Alan Orpin, said that in the upper canyon, there was evidence of eroded old muddy seafloor with fresh deposits of soupy mud on top.
"In the lower canyon we sampled gravel waves, comprising well-rounded greywacke pebbles," Orpin said.
This picture of the Kaikoura Canyon seabed shows a dense bed of tubed forams and a rattail fish - a survey in January showed nothing living there. Photo / NIWA
"We think that these waves were reshaped by powerful sediment-laden flows triggered by the earthquake."
The NIWA team also included scientists studying the structural and chemical changes in the canyon sediments, as well as biologists looking for signs of recovery in the animal communities by taking core samples and video of the seafloor.
Scientists aboard NIWA's Research Vessel Tangaroa sieve mud samples from Kaikoura Canyon. Photo / NIWA
Biogeochemist Dr Scott Nodder said there was a widespread "fluffy muddy layer" on the seafloor surface characteristic of the upper canyon.
"This is different from samples collected from the shallower Conway Trough that branches south off the main canyon," Nodder said.
Seabed cucumbers and a rattail fish. Photo / NIWA
"There, our first impressions suggest less impact of the earthquake on the seabed environment."
Dr Ashley Rowden, the overall leader of NIWA's Kaikoura Earthquake deep-sea project, was pleased to hear about the results.
"Following the earthquake, the people of Kaikoura have had to deal with a lot of disruption, economic troubles and other issues.
NIWA scientists hoist a multi-coring device used to take seabed samples in Kaikoura Canyon. Photo / NIWA
"So, it is good to find indications that the deep parts of the canyon - which contribute to maintaining a healthy functioning ecosystem on which some of the community rely - is beginning to recover."
In the days after November's Kaikoura Earthquake, volunteer paua rescuers arrived at the raised coastline searching for stricken shellfish put in danger. Photo / File
Meanwhile, the Government has just funded another $3.1 million new study focused on Kaikoura's wider post-quake marine environment.
The quake brought unprecedented changes to the coastal ecosystem along 130km of the South Island, uplifting of the nearshore zone by up to 6m and raising formerly subtidal rocky reefs out of the water.
Many species, such as paua and a critical kelp bed habitat, were lost, while the erosion of newly exposed sedimentary rocks deposited fine silt over rocky reefs extending far out to sea, smothering many bottom-dwelling species.
Full recovery was expected to take years.
A new study, supported by the Government's Endeavour Fund and to be led by the University of Canterbury's Distinguished Professor David Schiel, aims to understand the lasting consequences of the event.
Incorporating Matauranga Maori, or Maori knowledge, it would explore potential ways the environment could adapt and recover, and how safe havens provided by Customary Protection Areas such as rahui, taiapure and mataitai areas might help.
The project will also build on a 25-year data set of sampling experiments around the coastline, testing how much small-scale experiments can tell scientists about the bigger picture - and whether the same lessons can be applied in future disasters.
