Update: Bioluminescence has reappeared across the Northern Beaches, with sighting at Freshwater and Manly late last night, 11 January
Previously: Brilliant blue bioluminescence had lit up almost every beach on the Northern Beaches overnight, Thursday 28 December 2023, attracting crowds late into morning.
The phenomena, most likely Noctilluca Scintilla or sea sparkle or sea twinkle, is caused by a red algae.
Algal blooms occur in response to changes in temperature or rain or nutrients in the water. They are little organisms, so while not toxic to humans it can cause a bit of skin irritation.
It first appeared on Wednesday night at Palm Beach and has since made its way along Warriewood, Dee Why, South Curl Curl, Freshwater and Manly and Shelly Beaches.
Will there be more bioluminescence in Manly or elsewhere on the Northern Beaches tonight?
The short answer is, we don’t know. But the most common times it appears seems to follow the rising tide, which will peak at Manly at 11:14pm this evening. If there is to be any magic on show, from 9pm until midnight is the best chance of it. We have had reports of what seems like “lots of blood” through Manly to Cabbage Tree Bay which could either be debris from a recently deceased sunfish or a sign that there is plentiful algae already in the bay, as this is a rusty red colour when viewed in daylight.
The bioluminescent sea will glow when it’s disturbed by a wave breaking or a splash in the water at night, and is noticeable when there is a large volume and the wind is gentle enough to allow it to stay on the water’s surface rather than sink below. Should the conditions be right, be sure to tag us on socials @manlyobserver so we can let others know where to enjoy the show.