Bosphorus Strait turns bright blue due to plankton superbloom

Locals, initially worried it was pollution, have been reassured the colour is down to micro-organisms

Blue and tranquil, the busy waters of the Bosphorus are good-looking enough at the best of times. But this week they’re even more Instagrammable than usual, having been turned bright turquoise by phytoplankton.

The Bosphorus Strait, which slices through Istanbul, dividing the continents of Europe and Asia, has long been one of the main attractions of Turkey’s largest city. The Galata Bridge is full of locals fishing, the shore of Kadikoy on the Asian side is scattered with cafes looking out towards the European side, and the ferries that ply the waters rank as some of the most scenic commutes in the world.

But this week, the famous waters turned bright turquoise, after a surge in the Emiliania huxleyi (or Ehux) plankton in the Black Sea.

Locals, initially concerned that it might be due to pollution, quickly took to social media to share photos of the colours

Others had worried it might be linked to Monday’s earthquake.

The effect was so startling that even Nasa tweeted a photo of the Black Sea. On its website, it describes the phytoplankton “bloom” as an annual occurrence.

“The May ramp-up in reflectivity in the Black Sea, with peak brightness in June, seems consistent with results from other years,” ocean scientist Norman Kuring told Nasa. 

However, he added that it was one of the brightest of the past five years.