Turquoise Waters Observed along Black Sea Coast in Bulgaria as Phytoplankton Bloom Alters Sea Colour

For nearly a week, the waters of the Black Sea have taken on an unusual turquoise hue, drawing the attention of residents and tourists along Bulgaria’s southern Black Sea coast.

The unusual blue-green shade of the water is due to a mass bloom of phytoplankton – microscopic algae that develop in spring under favourable conditions. Increased sunlight, warmer water temperatures, frequent rainfall and sufficient nutrients create an environment conducive to their rapid growth.

Although individually invisible to the naked eye, in large concentrations they can alter the colour of seawater. According to specialists, the phenomenon is entirely natural and does not pose a danger to humans.