Some species living amid White Island's underwater reefs were likely wiped out in Monday's eruption – but a marine scientist expects any affected populations will quickly bounce back.

The island is a popular spot with divers for its dramatic pinnacles with 150m drop-offs and a colourful abundance of sea life, ranging from schools of pink maomao to packhorse crayfish.

Waikato University's Professor Chris Battershill said he'd been planning another survey of the island's marine ecosystem when Monday's eruption occurred, belching ash more than 3km into the air.

Given how much ash and material would have fallen into the environment in such a small amount of time, Battershill expected some sensitive species like sponges would've been killed off.


But, because the island was bathed in a strong current field, most of the species present would be able to repopulate – as was seen at Otaiti/Astrolabe reef after 2011's Rena disaster.

The downwind side of the island was also regularly exposed to volcanic runoff from the island – although in small amounts – and acidic ash and sulphur rained down on these reefs continuously.

White Island is also known for its stunning marine environment. Photo / White Island Tours
White Island is also known for its stunning marine environment. Photo / White Island Tours

"The seaweed beds on the downwind side are noticeably pale and in poorer condition than those upwind, and, under the kelp canopy, there isn't as much biodiversity," Battershill said.

"There's a fine layer of ash over much of the reef for significant periods of time in these areas - hence the marine assemblages there reflect this naturally ash-influenced fallout. It's like a rain shadow in reverse."

A reserve area at nearby Volkner Rocks would not have been affected, as it was well northwest of the immediate ash fallout area, he said.

As for pelagic fish in the area, like snapper and tarakihi, he suspected the impact would also be "negligible".

"With these free-swimming species that people target, if there is too much ash in the water, it becomes slightly acidic, and they sense that straight away and get out of there."

He planned to travel there when it was safe to do so.


University of Auckland marine scientist Dr Andrew Jeffs said the island's unique volcanic environment had been used for studies focused on what how sensitive organisms might respond to ocean acidification driven by climate change.

As for how species could have been hit by ash and sediment, Jeffs said the effect would be "nothing compared to the megatonnes that washes off New Zealand every year and into our coastal waters, largely as a result of our poor land management".