Why Do Lakes Sometimes Turn Pink?

A perfectly preserved medieval fortress, on the edge of a bright pink lake. It looks like a set from the Barbie film - and yet it's a real place, and it's in France. But what exactly makes a lake turn pink? And how long does it stay pink? I hopped on a TGV to go and have a closer look... INSTA - https://www.instagram.com/the.tim.traveller TWIT - https://twitter.com/TheTimTraveller FACE - https://www.facebook.com/TheTimTraveller/ IMAGE CREDITS Lake Hiller by Aussie Oc - https://commons.wikimedia.org/wiki/File:Lake_Hillier_2_Middle_Island_Recherche_Archipelago_NR_IV-2011.JPG Laguna Rosada by Chad Ajamian - https://commons.wikimedia.org/wiki/File:Laguna_Rosada_2_Of_4_Yucatan_Mexico_%28248352743%29.jpeg Dunaliella Salina by Mike Dyall-Smith - https://commons.wikimedia.org/wiki/File:Microorganisms_from_the_hypersaline_Lake_Tyrrell.jpg Artemia Salina (brine shrimp) by Hans Hillewaert - https://commons.wikimedia.org/wiki/File:Artemia_salina_6.jpg Flamingo by Elgollimoh - https://commons.wikimedia.org/wiki/File:Flamant_rose_Salines_de_Thyna.jpg Beta-Carotene powder by 102% Yield - https://commons.wikimedia.org/wiki/File:%CE%92-Carotene_powder.jpg Carrots by domdomegg - https://en.wikipedia.org/wiki/Carrot#/media/File:Carrots_at_Ljubljana_Central_Market.JPG