Aussie baffled as water in popular lake turns pink

The reddish pink tides have also been seen in Manly, with locals flocking to the area to enjoy the unusual sight.

A “strange” reddish substance that appeared at a popular NSW lake has left an inquisitive local puzzled, and others eager to check out the “awesome” sight in person.

The surprised woman came across the bizarre scene at Lake Macquarie, north of Sydney, on Sunday and snapped two photos of the “pinkish/orange liquid on the water” hugging the shoreline at Bennett’s Park.

The red liquid on the shore of Lake Macquarie.
A woman was confused when she saw a 'strange' red liquid in Lake Macquarie. Source: Facebook

“Any ideas what it might be?” she posted on a community Facebook group. At first glance, one local said the substance appears to have been dumped in the water, while another joked it was the “fake tan from everyone who swam in the lake over the weekend”.

Despite some concerns the water is harmful, other residents assured the woman the sight was a “natural” phenomenon that occurs every year — an algae bloom often referred to as “red tides”. At night, when it’s been disturbed, it becomes bioluminescent, locals explained.

“It should glow at night also. Looks awesome,” someone said, while another added “it’s all over the lake at the moment”.

The red water at Lake Macquarie on the shore of a park.
The substance was revealed to be caused by a dinoflagellate type of algae, Noctilluca. Source: Facebook

Red tides often seen on NSW coast

After reviewing the images, UTS Professor of Freshwater Ecology, Simon Mitrovic, told Yahoo News Australia that without microscope identification it is difficult to be certain, but he believes the pinkish hue is “an algae that forms red scums (or a red tide)” commonly “caused by a dinoflagellate type of algae, Noctilluca”.

“These frequently occur on the coast of NSW,” he said, adding that “if the algae is showing bioluminescence” it may be due to Noctilluca scintillans — a type of dinoflagellate phytoplankton responsible for the nighttime glow.

The red water at Shelly Beach in Manly with locals swimming nearby. The bioluminescent blue water being kicked by someone at night.
A red tide was seen in Manly over the weekend, with locals flocking to Shelly Beach to enjoy the bioluminescent water. Source: Facebook

There were similar scenes at Shelly Beach in Manly over the weekend, with locals flocking to the beaches to enjoy the bright blue water.

“Usually they are at low concentrations in the water but blooms may become visible due to winds moving them to bays and beaches where they accumulate and may be seen by the naked eye as red scums or colourations on the water surface,” Professor Mitrovic said.

“Sometimes these blooms are also seen after rainfall runoff brings organic matter to coastal and estuarine areas as they can use this as a nutrient to grow.”

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