Bioluminescent plankton: 'It's the northern lights of the ocean'

The bioluminescent plankton light up when agitated by motion - either waves or predators

'It's the northern lights of the ocean."

This was Emma Tumulty's response to seeing a magical natural phenomenon on the coasts of Wales after years of hoping.

The light in question is an ethereal blue that flashes along the edge of a wave as is rolls in to shore.

It is caused by bioluminescent plankton, tiny creatures floating in the sea that have the ability to emit light when disturbed by a predator or motion.

This sets off a light display for onlookers on shore, who are coming in increasing numbers to Welsh beaches late at night to try to see the plankton for themselves.

Emma Tumulty had a "bucket-list wish" to see bioluminescent plankton in Wales after first sighting it in Thailand

As with other natural phenomena like the northern lights, the power of social media has both spread the word about it, and made it easier for people to share real-time information about where it has been spotted.

Emma finally hit the jackpot this June, ticking something off her bucket list as she saw the plankton in action in the early hours of the morning at Caswell Bay in Gower, Swansea.

The 42-year-old teacher from Cardiff first came across bioluminescent plankton when she was on a night dive in Thailand about 15 years ago, and at the time had no idea it could be seen much closer to home.

When she found out, she was determined to see it in her native country.

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"It started off when I did a trip to Anglesey three years ago to hopefully see the bioluminescence at Penmon Point because it's a really good place to see it," she explained.

Last year Anglesey photographer Gareth Mon Jones captured marvellous moving and still images there after five years of trying.

Emma was not so lucky. She stayed for a week and went out every night but to no avail.

Emma Tumulty captured her first sighting of bioluminescent plankton in Wales at Caswell Bay this month

She joined the Facebook group Bioluminescent plankton watch last year, which shares information with plankton seekers, and last weekend went with three friends for an overnight stay at Gower, determined to make it happen.

"It was a risk, but it was a risk worth taking. There's nothing like seeing it in Wales, on your own doorstep," she said.

"We surveyed three bays. I went to Caswell and there was nothing there, then we went to Oxwich and nothing there.

"Them we thought we'd try Caswell again. As we walked down the beach, it was so apparent. The water was glowing. It came in with a wave.

"It was so amazing we stayed for an hour. I would class it as the northern lights of the ocean."

Much like the northern lights, the bioluminescent plankton produce some incredible photographs

Emma finally left the beach at 2am but will be returning to a different location, Newton beach in Porthcawl, next weekend in the hope of catching it again.

What is her advice for those wanting to see it for themselves? "It's got to be very dark," she said. "No torchlight, no headlights."

There have been complaints, some posted on the group, about large numbers of people coming and shining torches at the sea, making it impossible for others to see the phenomenon, but Emma thinks it is possible people do not realise they do not have to illuminate it for themselves.

"When it came in [in Caswell], everyone was stunned and everyone's torches went off. People don't realise it needs to be completely dark. People were mesmerised and were in awe of nature."

Peter Boden-Ryan, who runs a holiday cottage business in the Swansea valley, was one of the founding members of the Facebook group and has seen membership rocket since it first started in 2017.

Peter Boden-Ryan has seen the bioluminescence Facebook group he help create attract thousands of members

"There was a couple of hundred members for the first year and the next year it snowballed and we had 10,000 people join," he said.

There are now nearly 38,000 people registered.

Peter says there is never any guarantee that the plankton will appear on any given night or location, which some people do not understand initially, and weather and tidal conditions can also vary greatly from sighting to sighting.

However, in his experience, the best places to spot it are on south-west facing bays, and generally on an incoming tide, at the moment between about midnight and 3am.

For Thomas Winstone, 44, a firefighter and semi-professional photographer from Brynmawr, Blaenau Gwent, the bioluminescence is another good reason to grab his camera and head for the coast night after night.

Thomas Winstone was a nature and astro-photographer before he began taking pictures of the blue-lit waves

He got involved with the Facebook group early on and found it a natural extension of the astro-photography he was already doing, as the beaches of south Wales are a good spot for capturing the night skies.

"You're there at night, at two or three in the morning. You look at the images and you're like, what's that blue glow on the waves?

"I couldn't get enough of it," he said, although he added: "You can still go out many times and not get anything."

But other times he has almost been able to set his watch by the time the plankton will start to produce their show based on previous nights' experiences.

Thomas gets up close and personal with the bioluminescent plankton he loves to photograph

Although many plankton hunters will move from beach-to-beach as reports of sightings come in online, he prefers to stay in one place, having had enough experience of moving only to then find people have later seen the lights at the very place he left.

And he says the whole experience, whether or not the plankton appear, is great for body and mind and better than "sitting inside watching Eastenders or Coronation Street".

Although the growth in numbers looking for it can cause issues, he thinks it is a question of gently educating people about the best way to go about it.

"The problem with a lot of people going is torches and headlights on. They think they need the lights on to see it - no, it glows by itself.

"Obviously [we are] trying to keep people safe if they need to traverse a rocky beach" he said, adding people could use torches to get down but turn them off once they were on level ground.

Thomas is "one of the fanatics" who will go out multiple times in a week to try to see the plankton

"There's definitely a lot more people coming because of the publicity behind it and social media."

However he added: "It's the start of the season. People will see it once and they're happy.

"It's only the fanatics like me that are out three or four nights a week."

From his workplace, Christopher Lowe, a marine biology lecturer at Swansea University, has easy access to the Swansea bay and Gower beaches where hopeful spotters are keen on gathering.

The recent period of sunny, settled weather has meant a particularly good year for plankton conditions, with clearer seas than normal, he explained.

Christopher Lowe said the recent dry weather had produced great conditions for plankton displays

"If you go out to the Gower now, you'll see the water is quite blue and that's because a lot a sediment has settled out of the water. That means more light available for these plankton to be able to grow," he said.

He said the seas had seasons, similar to the ones on land, and the combination of nutrient-dense waters in the spring and the light created the perfect conditions for phytoplankton, or plant plankton, to grow, and animal plankton to come and feed on them.

"The fun thing is, a lot of these organisms will produce light. The reason they do that is a predator avoidance mechanism," he explained, adding it would either startle the predator or potentially light it enough so it became prey for another creature.

But the motion of the waves, or even someone throwing a rock into the sea, can set off the same response.

"The wave movement is the same as they would feel if there was a predator nearby, so they all flash at the same time and that's why we get these beautiful displays of the bioluminescence."

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