Dark secret behind stunning nighttime scenes in Sai Kung
Top News | Sophie Hui and James Lee 14 Mar 2022
Sai Kung's coastline twinkled a stunning blue at the weekend as people shared photos of the phenomenon online.
Known as "blue tears" the phenomenon is caused by a single-cell organism called Noctiluca scintillans, whose glow illuminated High Island Reservoir East Dam, Pak Lap Wan, and Po Pin Chau in Sai Kung.
Over the past few nights around Sai Kung, blooms of single-cell organisms called dinoflagellates have appeared, turning the water's edge blue and drawing the curious out to the beach at night.
The phytoplankton are nicknamed "sea sparkles" but their actual scientific name is Noctiluca scintillans, which literally means "twinkling night light."
One of those who just had to see the blue wonder was Max Yau, who was at the East Dam of High Island Reservoir at 3.30am yesterday.
"I've heard many people talking about this on the internet before, but it was my first time to see it with my own eyes," Yau told The Standard.
"At about 3.30am, the blue sea water suddenly emerged. The scene was magnificent and stunning."
The blue glow - which Yau said could be seen until 5am - was named one of the 15 "most awesome, must-see" natural scenes of the world by CNN in 2014.
It is, however, linked to water pollution. University of Georgia oceanographer Samantha Joye has said it is caused when Noctiluca reacts to a high concentrations of nitrogen and phosphorus - chemicals abundant in agricultural pollution and household sewage.
Although Noctiluca does not produce harmful chemicals, the organism can indirectly exacerbate the accumulation of algae toxins in seawater. Their growth near the surface of the water may also deplete oxygen levels, causing other organisms to die and disrupting the ecosystem.
In recent years, waters in Sai Kung, Repulse Bay and Deep Water Bay have been lit up by the algae.
