The Bosphorus has changed color. Since last weekend, the waters of the Bosphorus Straight in Turkey, usually deep blue, have become turquoise. Natural phenomenon or pollution?
It is a natural phenomenon that happens almost every year, but that continues to surprise the inhabitants of the Bosphorus Straight. Since last weekend, the waters of the Black Sea, usually deep blue, have become turquoise. Local residents first thought of pollution or the consequences of the earthquake that hit Greece and Turkey last Monday.
But scientists have a much more reassuring explanation: the appearance of a certain type of plankton, the Emiliania Huxley is is the cause of the change of color. It is a very widespread species of marine phytoplankton that plays an essential role in regulating the carbon dioxide content of the atmosphere. This unicellular organism can as well survive in equatorial and subarctic waters. Fabrice Not, researcher of the CNRS at the biological station of Roscoff in Finistère explains that to develop, this micro alga needs three factors: “light, nutrient salts and an optimum temperature. When these three elements are united, the species will thrive, then we speak of efflorescence, or bloom.
The spring in the Istanbul region was also rather rainy. The precipitations carried nutrients from the Sahara into the Black Sea. “At this season, the temperature of the water and the luminosity increase, the rain was thus the third factor that triggered the proliferation of the phytoplankton,” continues the researcher.
The turquoise color is due to the limestone that covers the plankton. Fabrice Not indicates that “limestone, when present in large quantities, tends to give the water a milky luster.” The phenomenon has even been captured by the NASA satellites.
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