Unusually warm water has brought on early plumes of Noctiluca scintellans, the algae that causes bioluminescence in Mahurangi.
While Mahurangi and the Hibiscus Coast have long been known as bioluminescence hotspots, it is perhaps less well known that the same algae also causes red blooms during the day.
Residents of Mahurangi West took to social media last month, concerned by thick red plumes on the surface of the harbour, fearing it had become polluted.
Auckland Council environmental scientist Dr Megan Carbines says that Noctiluca scintellans is a non-toxic dinoflagellate, which often forms bright blooms around the coast in summer.
When disturbed, it also emits a burst of light, often seen when swimmers or boats move through the water at night.
Dr Carbines, who has lived at Leigh for 10 years, has seen “spectacularly large” red blooms in the Leigh Harbour.
“The water temperature is increasing at the moment, which is conducive to these sorts of blooms if combined with calm conditions allowing them to accumulate.”
According to www.haurakigulfweather.com, harbours in the Auckland region reached up to 22 degrees last month.
That is about two to four degrees above normal for this time of year.
This was due to a La Niña weather pattern delivering warm and dry air.