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The amazing spectacle of electric blue light flashing in the sea has been drawing people to an Anglesey beach to marvel at the natural phenomenon.

The light, caused by clouds of millions of plankton and captured in these stunning images by photographer Kris Williams, has recently been seen at Penmon on the island’s east coast.

The bioluminescence occurs when the plankton are disturbed, resulting in an incredible light show.

Mr Williams, of Beaumaris , who takes landscape photographs as a hobby, described the phenomenon as like “lightning” in the water.

He said: “I’ve seen it five or six times in the last 12 to 18 months, and always at Penmon.

“You tend to see it at high tide and you need a bit of movement to stir up the plankton. Some displays are stronger than others, but it’s incredible to watch.

“Sometimes it’s very localised and only affects one spot, but at other times it stretches a long way along the coast.

“When the waves break, it almost looks like a lightning storm in the wave. When you walk on the pebbles at the water’s edge, the pebbles light up.

“A group of people came to the beach at Penmon on Sunday night and spent hours throwing rocks into the water to see the colour. You could put your hand in the water and watch it light up, then see the glowing particles slipping through your fingers.”

Dr Andy Davies, a marine biologist at Bangor University’s School of Ocean Sciences, said: “The light is created by small organisms called plankton, which are producing this light through a complex chemical reaction.

“This whole process is known as bioluminescence. Many organisms use very similar methods to produce light, including fish, jellyfish, squid and even fireflies. It’s an example of how organisms have evolved complex responses to external stimulus.

“Organisms generally use the production of light as a defence against a predator. It may serve to distract the predator or even attract a predator of that predator, giving them valuable time to escape.

“What we see at Penmon happens on many beaches around the world. Currents, waves and tides move plankton into the bay and, as the numbers of plankton increase, so does the potential brightness of the light.

“In this situation, the light is often triggered as a wave comes in, causing stress to numerous individuals who then produce light and create the glorious display we saw at Penmon.”

Dr Davies said he had seen bioluminescence only twice in five years, but advised that late spring and early summer are the best times to see the phenomenon.

He said: “It’s a fairly infrequent sight for people in Wales. It can just be a random occurrence in Penmon, but the Menai Strait is known for being highly productive, pushing lots of water and nutrients into the waters around Penmon and Conwy Bay, which creates ideal conditions for plankton growth.”