Deadly Sea Sparkle

Sea Sparkle (also know as Sea Ghost or Fire of Sea) is a natural phenomenon caused by Noctiluca Scintillas, a bioluminescent algae that occurs in ocean waters around the world. These tiny sea creatures feed on plankton, and when disturbed by waves can produce a wonderful and eerie blue light (using the same chemical reaction that makes fireflies glow). However, don’t let the beautiful glow fool you, Noctiluca Scintillas produces a powerful neurotoxin and is a sign of poor water quality.


Photograph by Hans Hillewaert.

The occurrence of Sea Sparkle in the waters off Hong Kong was recently reported in the Washington Post. While the eerie glow may make for stunning photographs, it can be a sign of poor water quality and a potential source of dangerous levels of neurotoxins.

Noctiluca Scintillas, the algae responsible for Sea Sparkle, occurs naturally around the world and feeds on plankton. Usually, there is not a lot of plankton around for Noctiluca Scintillas to feed on, and so its population stays low and unnoticed. However, the right mixture of sunlight and nutrients can lead to an explosion in population for both plankton and plankton eaters alike. These “algae blooms”, as they are known, are a source of water quality impairment around the world.


Microscopic view of Noctiluca Scintillas.
Photograph by Maria Antónia Sampayo.

Why are algae blooms so bad? Algae blooms are associated with aquatic “dead zones”, area in which aquatic life cannot exist due to poor water quality. Algae blooms deplete the level of dissolved oxygen in water, causing other sea life to die by asphyxiation. Some algae also produce toxins, ranging from ammonia to powerful neurotoxins, that also kill off other sea life. These “dead zones” can stretch for miles and persist year-round, and present a serious threat to water ecology.

Most algae blooms that occur today are the product of pollution from cities and agriculture. The overuse of fertilizers and poor water management in both cities and on farms leads to unnaturally high levels of nutrients in waste water. This nutrient pollution is feeding algae blooms and “dead zones” in waterways around the world. Better management practices, including reduced use of fertilizers and smarter use of water, would help alleviate this growing and serious problem.

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