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HomeNewsSEA-ING RED: What's that funny coloured plume in the water?

SEA-ING RED: What’s that funny coloured plume in the water?

A strange pink or perhaps rusty orange suspected algae plume has been sprawling around the Bower between the Manly and Shelly Beach stretch since dawn this morning, 1 December, causing locals to ask, “Is it safe to swim?”

The short answer is, best not. The upside is the chance of a light show in the water this evening thanks to bioluminescence. It’s not a definite, but it’s a maybe.

We understand a few samples have been sent off to the experts and will report back any findings, but in the interim regulars down at the Bower say it’s likely  Noctilluca Scintilla or sea sparkle or sea twinkle, a red algae which often comes out in the sun after long periods of rain, such as we have experienced the last fortnight.

Northern Beaches Council said it has been made aware of a marine algal bloom at Cabbage Tree Bay, Manly.

“The algal bloom currently appears as a brownish to red discolouration throughout the water. Algal blooms usually occur off the coast when there are increased nutrients and warmer water temperatures.

“The NSW Metropolitan and South Coast Regional Algal Coordinating Committee has noted that blooms from two marine algae species, Trichodesmium and Noctiluca, have been sighted at metropolitan beaches in recent weeks.

“These species are not considered toxic. However, the health impacts of marine or estuarine algae species is largely unknown so caution should be exercised where blooms occur. Contact should be avoided as skin and eye irritations may occur.

“Council environmental officers will continue to monitor the algal bloom and provide advice as required.”

So it’s best to avoid swimming in it for now as it can cause a bit of a skin rash thanks to the high level of ammonia.

The arrival of the suspected algae, which changes from red to pink to an orangey rust colour, could be a sign that the stunning phosphorescence or bioluminescence will be visible this evening or throughout the week around Manly.

In late October the Northern Beaches was treated to a bioluminescence spectacle caused by a plankton algae bloom.


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Manly Observer is an experiment in providing non-sensationalist hyperlocal news on Sydney’s Northern Beaches. We cover the big news across the LGA, but with a hyper focus on the Manly electorate encompassing Balgowlah, Seaforth, Freshwater, Brookvale and Curl Curl up to Dee Why. It is run by those living in the community for the benefit of an informed community. We care about an informed and connected community. That’s it. Simple. Thank you for your support in keeping quality local news alive!

Kim Smee, Editor

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