On the edge: How quake recovery is no shore thing

Researchers capturing the Kaiko¯ura coast tell Alice Angeloni that ecosystems are recovering, but not all is well.

Lush seaweeds used to run along the coast from Kaiko¯ ura to Marlborough, while beds of beaded brown algae supported some of the greatest biodiversity on New Zealand’s seashores.

More than three years on from the magnitude 7.8 earthquake in Kaiko¯ ura, researchers say recovery is going well in some areas, and not in others.

‘‘These ecosystems developed over tens of thousands of years, and were greatly altered in a matter of a few minutes by the earthquake,’’ University of Canterbury researcher Dr Shane Orchard said.

In many places, vegetated intertidal zones had been compressed into relatively small, near-vertical areas instead of the large flat platforms they once occupied, he said.

‘‘Another major impact is the great amount of sediments pouring out of earthquake-damaged hills during rain events (which have) buried parts of the seashore and smothered everything that occurred there, including recovering seaweeds and pa¯ ua,’’ Orchard said.

‘‘All of this tends to affect the recovery of the ecosystem.’’

Orchard is part of the Marine Ecology Research Group’s Recover project that is monitoring and assessing the ongoing changes to the coastal ecosystem.

Professor David Schiel, who leads the group, said the intertidal and shallow subtidal zones of the rocky shores had thick seaweeds from Oaro to Cape Campbell before the earthquake struck.

Some of these areas had been monitored regularly since 1992.

The areas more sheltered from waves had dense beds of the beaded brown algae, while waveexposed areas had similar beds of bull kelp, which supported many other species and helped protect the shoreline from erosion.

‘‘Most of these seaweed beds perished after the earthquake,’’ Professor Schiel said.

The research group was on site within a week of the earthquake to survey coastal platforms. The devastation of the ecosystem was ‘‘astounding’’.

Around Waipapa, with the greatest coastal uplift of about six metres, ‘‘entire algal beds that had been formerly submerged were left high and dry’’.

‘‘We stood under large boulders where drying bull kelp, several metres long, hung down from above, slowly baking in the sun.

‘‘Tonnes of pa¯ ua were exposed and died within a matter of a day or two, despite the best efforts of the populace to get at least some of them back into the water.’’

Thousands of fish and lobsters were dead along exposed reefs and many fish that came inshore to forage were stranded, he said.

‘‘The stench of dying seaweeds and animals was, in places, overpowering.’’

The waters inshore were ‘‘inhospitable’’ because of microbial activity from decaying organisms.

‘‘None of us, and few people worldwide, had ever witnessed such ecosystem destruction.’’

Fast-forward three years, and ‘‘recovery is good in some areas and not good in others’’.

Pa¯ua populations were recovering remarkably well and even though there was massive destruction of inshore recruitment habitat, there had been good growth over much of the coastline.

However, large bull kelp was missing from much of the coast, and many large platforms of algae may not return.

The group was aiming to help the coastline find a ‘‘new normal’’ post earthquake.

Waipapa North at low tide, above, shows "very little evidence of algal recovery" three years after the earthquake, says researcher Dr Shane Orchard. Left, bull kelp and other seaweeds recovering at Cape Campbell in Marlborough. Below, a sleeping seal on the rocks at Waipapa South demonstrates how the drone’s low-noise propellers reduce disturbance.

This photo, above, was taken a few months after the earthquake showing the massive uplift of the seabed at the Kaiko¯ ura Peninsula. Right below, new intertidal lagoon areas and shifting gravels can now be found at Waipapa where the reefs were uplifted as much as six metres.

Right above, intertidal algae is making a comeback on the edges of a flat reef platform at Wairepo, says Dr Shane Orchard, however the extent to which it will continue to colonise remains to be seen.