[Allan Burgess]

‘Severe’ marine heatwave to hit South Island waters

West Coast waters are set to reach 18.4C this week. (File photo)

The water temperature in the South Island is set to soar this week as a marine heatwave sweeps the West Coast.

It’s expected to reach a whopping 18.4C – five degrees hotter than the average water temperature for this time of year.

A marine heatwave is when water temperatures stay in the warmest 10% of what has been historically observed for at least five days.

MetService oceanographer Dr Joao de Souza said although the balmy waters would be good news for holidaymakers, they could harm marine life.

“Last year, a similarly warm marine heatwave in Fiordland reached great depths and caused widespread bleaching of sea sponges,” he said.

The native sea sponges, which should have been a velvety brown, were bleached white en masse as the heatwave ripped through the lower south Island.

Scientists were left in shock, but sea sponges are hardly the only ocean critter to be blighted by rising temperatures.

Salmon farms in the Marlborough Sounds were plagued with higher-than-usual deaths in the warm water last year.

Get the full story by Gabrielle McCulloch, Jan 02 2023, on Stuff.co.nz

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