Chch Dilemmas: Sea change at Kaikoura video

Christchurch Dilemmas / YouTube

Just after midnight on 14 November 2016 the Kaikoura coast rose up out of the sea - up to 6 metres in places. How has aquatic life coped with such incredible upheaval? What is the sea of green now carpeting the rocks, and will the reefs ever recover?

It would have been an incredible event to witness, if it hadn't happened in darkness, just after midnight on the morning of November 14, 2016.

A 7.8 magnitude earthquake forced a 110 kilometre stretch of the Kaikoura coast to rise up from the sea. The uplift varied, from half a metre to almost 6 metres at Waipapa Bay.

Aquatic creatures and marine vegetation which had lived mostly underwater, struggled to adapt to a terrestrial world. Especially hard hit were slow-moving species such as limpets and paua, and thousands of them perished under the summer sun.

An uplifted seabed.
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An uplifted seabed.

Today, it's easy to identify areas of uplift, most platforms are covered by a carpet of green algae, commonly known as sea lettuce.

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It's flourishing in the new, drier environment.

A dying kelp plant.
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A dying kelp plant.

Shawn Gerrity and Tommaso Alestra, Marine Ecology Researchers from the University of Canterbury, are working with the Ministry of Primary Industries (MPI) to monitor the effects of the uplift on marine life.

Both men were familiar with the environment, having spent many hours studying the Kaikoura coast pre-earthquake.

Alestra says "it's quite upsetting because over the years doing my research here around the peninsula i got to love these reefs."

A carpet of green now covers the once diverse reefs of Kaikoura.
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A carpet of green now covers the once diverse reefs of Kaikoura.

He says the reefs have changed a lot, there have been massive die-offs and they are "bare and empty now".

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Except for the sea lettuce.

Gerrity wants to determine if the presence of the sea lettuce is slowing down the recovery of other algal species and invertebrates.

Dead kelp stumps in an area once below the water.
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Dead kelp stumps in an area once below the water.

Certainly the wait for paua to re-establish will be a lengthy period, and may involve a decade-long closure of the paua fishery.

"How long are they going to take to recover, to the point where it could sustain the recreational fishery?" asks Gerrity. "We don't know yet."

Another struggling species is bull kelp. Alestra says it could take years for stocks to recover.

Green algae shows the new tidal levels on the Kaikoura coast.
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Green algae shows the new tidal levels on the Kaikoura coast.

"Many plants were lost because they were not able to survive the heat and the dislocation from the uplift," he says.

Local, long-time fisherman, Paul Reinke, has been able to continue his crayfish operation.

The rock lobster fishery was closed for a month after the earthquake, during which Reinke and others assisted MPI in surveying crayfish numbers.

He operates out of South Bay where the uplift was around a metre.

"For months you couldn't get your head around how low the tide was."

The uplift may have taken just a few, spectacular seconds, but for many plants and animals the impact will be felt for many years, though according to Tommaso Alestra, no species have been lost entirely.

"I hope they can little-by-little recover and come back to what they used to be like."

 - The Press

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