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Marine uplift from Kaikoura earthquake - Expert Reaction

Marine uplift from Kaikoura earthquake - Expert Reaction
16 November 2016

We're gathering expert commentary on various aspects of yesterday's magnitude 7.5 Kaikoura earthquake and the resulting aftershocks and landslides.

“The images of uplifted rocky reefs covered with dying paua, crayfish, and seaweeds are striking. The extent of this uplift is not yet clear—but without question, the affected areas will experience significant changes in the quantity and composition of marine life. Recovery could take years. And the ‘recovered’ state could look quite different.

“The seaweeds and animals that inhabit these areas are remarkably resilient. They tolerate pounding by large waves and the rise and fall of the tides every day. They produce large numbers of offspring that can travel great distances to replenish distant sites. But they are also carefully tuned to their environment, and they are incredibly sensitive to water depth and tidal levels. Changes that take a long time to happen will have comparatively little effect, because organisms can respond with adjustments to their physiology and/or a shift in their distributions over many generations. Changes that happen quickly are a problem.

“We know that small changes in tidal fluctuations can have big effects on the marine life in these communities. Rapid coastal uplift (or subsidence) will have ecological consequences that are even more severe. The effects of a coastal uplift (of 40-60cm) following an earthquake that struck Chile in March of 1985 is particularly well documented: the affected sites experienced catastrophic mortality of many species (including important habitat-forming seaweeds). Recovery took years.

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“Recovery will happen along the Kaikoura coastline. Remnant populations of affected species may be present beneath the new land-sea interface, and at nearby locations that did not experience uplift to the same extent. Offspring produced by these populations will replenish affected areas. Some species will take longer than others to recover. And much will depend upon what happens to important habitat-forming seaweeds.

“One silver lining—the Kaikoura system is among the best-studied coastlines in New Zealand. Researchers with long-term data on this system will be well-placed to make predictions. And continued monitoring of this system in the aftermath of the uplift event will strengthen our scientific understanding and enable us to make even stronger predictions in future.”

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