Life returning to Kaikoura seabed
Samples from canyon floor devastated by earthquake show littlest residents recovering faster than expected
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-sea ecosystems 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 changes 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 deepsea 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.
“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 [directly] above the seabed.”
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.
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.
Dr Ashley Rowden, the overall leader of Niwa’s Kaikoura Earthquake deep-sea project, was pleased with the results.
“Following the earthquake, the people of Kaikoura have had to deal with a lot of disruption.
“So, it is good to find indications that the deep parts of the canyon — which contribute to maintaining a healthy ... ecosystem — is beginning to recover.”
Meanwhile, the Government has just funded a new $3.1 million 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 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.