It’s electric — the sparky science behind tidal light shows

In May, the sea along various shorelines in Kent lit up with magical electric blue lights on particularly dark nights.
“It was so visible to the eye,” Rebecca Douglas, a photographer, reported from near Margate. “Electric blue [light] appearing as the waves crashed in.”
Similar blue lights also appeared along the shores of Dunraven Bay in South Wales.
This was a phenomenon called bioluminescence, described by Charles Darwin onboard The Beagle off the coast of Tenerife in January 1832: “The sea was luminous in specks . . . When the water was put into a bottle, it gave out sparks.”
This bioluminescence was created by masses of plankton, microscopic creatures floating in the sea that burst with light when disturbed, often by waves or predators. One common flashing plankton has the evocative name Noctiluca scintillans, though it is also known as sea sparkle, and flashes its light when disturbed.
Another type of bioluminescence is even more remarkable. For centuries, sailors were amazed by the sea glowing as far as the eye could see. Unlike the flashy plankton, this type of bioluminescence creates a steady and eerie milky white glow over vast areas of sea, usually in the tropics, and is created by bacteria.
On January 25, 1995, the British merchant ship SS Lima was sailing at night in the Indian Ocean. “On a clear moonless night . . . the ship was completely surrounded by a sea of milky-white colour,” the ship’s log recorded. “It appeared as though the ship was sailing over a field of snow or gliding over the clouds.”
The glowing sea covered hundreds of square miles of ocean, an area so large that the light was detected by a satellite, and using the sea and weather conditions at the time, scientists worked out that warm sea surface temperatures, large amounts of bacteria and ocean currents were all needed for the bioluminescence.
A recent study also found that this luminescence shields bacteria from damaging ultraviolet rays in sunlight, which is channelled into bioluminescent proteins that release the energy as light.