Seal Swims Through Bioluminescent Plankton in Nieuwpoort
A seal has been captured on video swimming through bioluminescent plankton off the coast of Nieuwpoort in West Flanders, Belgium, creating a stunning blue glow that witnesses have described as a magical phenomenon. The footage, taken by local nature guide Luc David, shows the seal gliding through waters illuminated by Noctiluca scintillans — commonly known as sea sparkle or “zeevonk” in Dutch.
A Rare and Magical Sight
Luc David, a well-known nature guide from Nieuwpoort who won the city’s Groene Pluim environmental award in 2012, captured the remarkable footage during a period of warm, calm weather along the Belgian coast. Speaking to Het Laatste Nieuws, David described the experience: “The weather is right for it. This is a magical phenomenon.”
The article, published by journalist Gudrun Steen on May 29, quickly became the most-read and most-shared story on HLN, underscoring the public’s enduring fascination with natural wonders along the Belgian coast.
What Is Zeevonk?
Zeevonk, scientifically known as Noctiluca scintillans — Latin for “flashing night-light” — is a single-celled dinoflagellate less than one millimeter in diameter. Despite its microscopic size, when conditions are right, these organisms gather in vast numbers and produce one of nature’s most dazzling displays.
According to Onze Natuur, the blue glow is produced through bioluminescence — a chemical reaction that occurs when the algae are disturbed by movement in the water. This serves as a defense mechanism to startle predators. During the day, high concentrations of the algae give the water a salmon or reddish tint, but at night, the same organisms emit a brilliant blue light when agitated.
David explained the phenomenon simply: “Sea sparkle is a large single-celled alga with a diameter of less than a millimeter. Because the alga is so light, it floats on the water. During the day it is salmon-colored, but at night it turns blue. These algae are completely harmless. Just enjoy it is the message.”
When and Where to See It
The bioluminescent plankton can be observed along the entire Belgian coast until August, with the best conditions being warm, windless days with calm seas. The contrast is greatest after midnight. As VRT NWS reported in previous coverage, the phenomenon typically occurs from mid-May through August when water temperatures rise above 25°C.
A Conservation Success Story
The sighting of a seal swimming through these luminous waters is also a testament to the recovery of marine life along the Belgian coast. According to Onze Natuur, both harbor seals and gray seals have been increasingly spotted along the Belgian coast, particularly in nature reserves like De IJzermonding near Nieuwpoort. The area has become a regular habitat for seals after decades of pollution and habitat disturbance drove them away.
Implications and Forward Look
While zeevonk blooms are natural events, their frequency and intensity can be influenced by water temperature, nutrient levels, and weather patterns — all factors affected by climate change. Warmer sea temperatures may extend the season for bioluminescent plankton blooms or increase their frequency along the Belgian coast.
For now, the combination of a charismatic marine mammal and a stunning natural light show has captured the imagination of the public. Luc David, who has been recognized by the City of Nieuwpoort for his environmental contributions, encourages everyone to experience the phenomenon responsibly.
As the warm summer months approach, conditions along the Belgian coast are expected to remain favorable for zeevonk sightings. Nature enthusiasts are advised to visit on warm, windless evenings after midnight for the best chance to witness this magical display — and perhaps catch a glimpse of the seals that have made this stretch of coast their home once again.