THE mystery of the unusual 'yellow slick' spotted on West Scotland shores this week has been solved.

We reported earlier this week on instances of cars and garden furniture being covered and of a yellow substance washing up on the tide.

Scientists from the Scottish Environment Protection Agency (SEPA) have now solved the mystery behind the paint-like substance.

Staff from SEPA’s national monitoring team collected samples of the substance from a stretch between Arran, Fairlie and Largs.

Largs and Millport Weekly News: Pollen bloom around edges of water on coastline spotted earlier this weekPollen bloom around edges of water on coastline spotted earlier this week (Image: Ian Dalgleish)

The samples were taken to the agency's marine ecology team based at Eurocentral near Motherwell.

They processed the samples and identified the strange substance as conifer pollen deposits.

Some members of the public had speculated on social media that pollen lay behind the slicks, but others wondered if it might be a more sinister pollutant.

Myles O’Reilly, senior marine ecologist from SEPA, said:“At this time of year, the public can expect to see yellowish slicks of pollen deposits collecting on shorelines around Scotland.

"In spring around April and May, conifer trees, such as spruce or pine, produce copious quantities of pollen.

"Conifer pollen grains have little buoyancy sacs to help them disperse in the wind, and these sacs also mean they float well on water.

“The pollen deposits can form a mat or slick on the sea, collect around the seashore and look like a paint-like substance covering rocks and beaches.

"It can also coat parked vehicles and stationary objects which may look like a yellow dust.”

SEPA's conclusion confirmed the hypothesis of Largs and District Horticultural Society president Ian Taylor, who said the phenomenon, which he had only witnessed once before, was only likely to happen during May.

Ian said he had seen the deposits while living in an area of France with "millions of pine trees".

Reports of the pollen deposits have been reported across Scotland with enquiries coming in from Inverclyde, Glasgow, the Hebrides, the Highlands, and Fife and Angus. 

While pollen is produced every year, a spell of warm weather can release a large amount at the one time.

These deposits are harmless to the environment and naturally occurring due to many trees of the same species, in this case conifers and spruce, growing together close to the sea.

When they all produce pollen at the same time, it collects on the shorelines. 

During the summer months, there may be other natural occurring events, including the presence of algal plankton blooms which can discolour water or form shoreline slicks or scums.

To report a pollution incident contact SEPA via their Pollution Hotline on 0800 80 70 60 or report an environmental event on their website at