Hong Kong's waters shimmer at night and it's not because of the city's lights. When disturbed, algal bloom produced by the Noctiluca scintillans glows blue, turning the water luminescent.

It's indeed a stunning sight to behold at night but during the day the situation is not as rosy. Officially, the algal bloom is referred to as red tide and it flourishes because of the pollution in Hong Kong's waters.

"Hong Kong and the entire Pearl River Delta has a big problem with wastewater, and that is surely a factor with these plankton blooms," explained David Baker from University of Hong Kong's Swire Institute of Marine Science.

On its own, the Noctiluca scintillans is actually no threat. It can co-exist with other flora and fauna in the water and is no danger to humans. The problem starts when the algal bloom grows to massive proportions.

While this means a bigger blanket of blue at night that will surely look mesmerizing, this also means algae overrunning the waters and depriving other plants and animals in Hong Kong's waters with oxygen.

But aside from competing with other organisms for sustenance at the surface, Noctiluca scintillans also endanger those at the bottom of the water when they die as the decomposition process they undergo large amounts of oxygen.

Areas where the algal bloom thrive and eventually die in get depleted of so much oxygen that they become unable to sustain marine life. As such, they are aptly called dead zones, and a number of them are found around Hong Kong's waters.

While Hong Kong is the latest place to showcase the Noctiluca scintillans, it is not the only place in the world with the beautiful but deadly problem. Algal blooms plague the world, reported in various parts of the world making their presence felt in waters where high levels of phosphorus and nitrogen are found, chemicals typical of farm run-off.

Hong Kong's shores sustains algal bloom because of residential sewage and restaurant waste running directly into the sea.

Noctiluca scintillans is a single-cell organism that consumes plankton and is then, in turn, eaten by other creatures in the water. It's not inherently dangerous because it does not produce chemicals capable of attacking those who eat it or tainting the waters it calls home.

Due to its striking glow, Noctiluca scintillans is also known as Sea Sparkle.