Hugemudslides revealed in Kaikoura canyon
Huge mudslides from November’s earthquakes have wiped out all organisms living in the seabed of the Kaikoura Canyon, which used to be a hotbed of life.
A survey a decade ago found the canyon had one of the highest volumes of organisms living in the mud known anywhere in the world.
It was a starkly different story when the canyon was recently resurveyed from Niwa’s research ship Tangaroa after the magnitude 7.8 Kaikoura earthquake on November 14.
‘‘We surveyed exactly the same area we did in 2006 and, while fish were still found in the area, this time didn’t record evidence of a single organism living on or in the seabed over a stretch of nearly six kilometres of seabed,’’ Niwa marine ecologist Dr Dave Bowden said on Monday.
‘‘It was quite sobering, and a catastrophic event for the ecology of the canyon.’’
Previously, the seabed was covered with burrows, tracks, pits and mounds made by seabed animals but it was now smooth and barren.
Fish and whales were seen in the area and it was not known what the consequences for those predators would be, Bowden said.
Changes in the canyon opened the way for some important research.
‘‘We suspect that events like this might happen every few hundred years in the Kaikoura Canyon. It will be very interesting to follow what happens from here, and I will be highly surprised if it doesn’t regenerate.’’
Other research has looked at changes to the head of the Kaikoura Canyon following the earthquakes.
During a week-long investigation Niwa marine geologist Dr Joshu Mountjoy compared maps of the canyon made in 2013 with the position in January.
‘‘In 2013 everything at the head of the canyon was smooth and draped in mud. Our new data shows that the earthquake resulted in a huge slipping event. Almost every part of the upper slope had mud removed from it.’’
Maps made last month show features of the upper slopes of the canyon in far greater detail, with large valleys and ridges once filled with mud, now completely cleared. The amount of debris that cascaded through the canyon was ‘‘massive’’, Mountjoy said.
‘‘Some individual landslides are more than three times the size of the landslides that damaged the road to the north of Kaikoura.’’
The combination of all the landslides was likely to be the source of a huge current detected by Niwa scientists shortly after the earthquake.
The rim of the canyon is close to the road south of Kaikoura Peninsula and has been studied in an ongoing project because of the potential tsunami risk.
Preliminary analysis indicated the likelihood of a damaging tsunami being generated from landslides in the canyon had not increased due to the earthquake, and may be lower than previously thought, Mountjoy said.
Ministry for Primary Industries (MPI) fisheries science manager Dr Shelton Harley said it would be important to understand how deep sea effects on productivity in the canyon affected the foodweb.
MPI is administering a $2 million emergency research package for the Kaikoura region covering a wide range of marine fauna of critical importance to the ecosystem and local community.
It covered rock lobster, paua, blue cod, sperm whales, fur seals, Hutton’s shearwaters and a range of intertidal and subtidal rocky reef animals and seaweed.
‘‘The results of this research will enable MPI to build a far better picture of the long-term effects and the most appropriate actions to manage sustainably for the future,’’ Harley said.