Known as a 'red tide' by day, the microalgae Noctiluca scintillans, known as 'sea sparkle', emits a bioluminescent blue glow when disturbed at night. Last May, residents of Hobart, Tasmania, were treated to a light show on the Derwent River, mostly around the South Arm Peninsula, as the dinoflagellate bloom has washed ashore.
The phenomenon looks interesting by day...
... but absolutely spectacular at night!
