A Barrock woman sent photographs she took during a walk on Dunnet beach yesterday afternoon as the sea and sand were tainted with a mysterious blood-red substance.

Linda Stewart moved to Caithness earlier this year when she retired and bought a house in the tiny hamlet of Barrock close to Dunnet beach where she enjoys a daily walk.

"It was around 5pm and driving rain so there was nobody on the beach," said Linda who enjoys the wide open spaces that the county has to offer.

"This particular beach is amazing but then I saw this rusty-red colour leaving lots of patterns on the sand. It was just incredible and I've never seen anything like it."

When she looked closer she said the mystery substance seemed to be composed of "little seeds" and stretched over 100 yards across the beach. "I should have got a handful and looked more closely but I'll be going again tonight. Mind you, the tide has probably washed it all away."

The Scottish Environment Protection Agency (SEPA) was sent the pictures and asked for a comment but was unable to respond at the time of publication. Red algae, known as Noctiluca scintillans or sea sparkle, has been seen at various locations across the globe and, though not particularly toxic, swimmers are advised to avoid affected areas due to possible cause skin irritations.

When an image was shared on social media Terri Watt said she rides her horse on the beach and came across the strange phenomenon before: "I’ve seen this a few times before at Dunnet Beach….it is some form of seaweed. You see it in the water too – makes the water like thick pink soup."

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Dorcas Sinclair picks up litter from Dunnet and other coastal locations across the county as part of the Caithness Beach Cleans eco group. She agreed that it was more than likely a type of seaweed.

"It's little red balls of weed that float individually but then wash up and end up making a carpet, they go light brown/grey as they dry out and the sun bleaches them."

Though it may appear quite alarming and possibly toxic, Dorcas reassured beach walkers that it is quite harmless. "Some people think that something has been spilled on the beach and it really is natural."

A possible human bone was recently discovered on the beach by German tourists and is being investigated by the police.

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