A view of the Bosphorus Strait on Wednesday after it turned turquoise due to a surge in a species of plankton across the Black Sea. The sudden transformation of Bosphorus' waters from its usual shade of blue to a milky turquoise since the weekend alarmed some residents. Some took to social media to express fears that there had been a pollution spill, while others even suggested it could be linked to an earthquake that rocked the Aegean region on Monday afternoon. But scientists said there was no mystery behind the colour change, which was accompanied by a sharper smell. Professor Ahmet Cemal Saydam, professor of environmental science at Hacettepe University, told the Dogan news agency that the cause was a surge in numbers of the micro-organism Emiliania huxleyi, also known as Ehux. "This has nothing to do with pollution," he said. One of the most successful life forms on the planet, Emiliania huxleyi is a single-celled organism visible only under a microscope. Its astonishing adaptability enables it to thrive in waters from the Equator to the sub-Arctic.