“Not every wave had it. The ones closer in and breaking on the shore didn’t have it. It was a bit further out. It would light up blue and run down the wave.”
The phenomenon, known as bioluminescence, is the product of certain species of microscopic plankton that can create light.
“I’ve never heard about it before and I am 78,” Cowell said.
She said high tide around 9.30pm was the best time to view it on Sunday night, and while her Samsung phone couldn’t capture the glow, a friend managed stunning shots with a professional camera.
“Lots of people were down there … It’s worth going to have a look.”
What causes the blue waves
University of Waikato Professor of Coastal Science Chris Battershill said certain species of plankton – particularly plant plankton such as dinoflagellates – can create light.
They do this to attract food, communicate with each other, or as a chemical response to their metabolism.
Disturbances in the water – a wave, a boat propeller, a dolphin swimming – triggered the metabolic response and caused them to glow.
Fast-warming seawater temperatures, longer and sunnier days, and a “bolt” of nutrients from the deep were behind the recent bloom.
“It’s a sign summer is on the way.”
Battershill said the bloom in Pāpāmoa was likely assisted by recent strong westerly winds.
Surface water pushed out to sea was replaced by an “upwelling” of nutrient-rich water.
Plankton feasting on this buffet could multiply rapidly, causing a bloom.
In his experience, this happened every three-to-five years, but he said it was happening more often as waters warmed.
Is it harmful?
The plankton were unlikely to harm most swimmers, though some species could cause rashes for people with sensitive skin, Battershill said.
If the bloom got “out of control” it could lead to a more toxic bloom, which could show up as a “red tide”, where the water would turn blood red.
The “productivity” in the water could travel up the food chain, attracting other, larger species.
Tauranga scientists and divers were already seeing long strings of salps and comb jellyfish, Battershill said.
He said the water was warming faster than he expected this year.
He said the water was 17C about two weeks ago. On Monday, MetService put it at 19C.
Battershill hoped it was not a sign of another marine heatwave, which could damage important parts of ecosystems.
How to see the bioluminescence
Battershill said the glowing effect could continue for days or weeks, depending on nutrients, warmth and sunlight.
It was best seen on a clear night with a bit of swell from the beach, or from a boat. Rain could subdue the effect.
“Right now is probably a good time to pop to Pāpāmoa on a nice clear night.”
Night-time beach visitors should take care to keep themselves and their children away from the water, especially in high swells.
Similar displays have recently been reported at Strathmore Bay, where the ocean was seen “glowing with thick, widespread blue bioluminescence as far as the eye could see along the beach”.
