October 1 drone video of the lake, now turned a deeper red hue

Effluents may be to blame

The chief suspect is the effluents from a nearby fish firm, RASA, according to the Buenos Aires newspaper Clarín. In July residents of Trelew denounced the stench of the effluents entering the lake over two years, and the insects and vermin they attracted, and were evidently dissatisfied when Juan Michelou, a senior provincial environmental officer, said "it'll pass, the lake will recover its normal color within days."

The pink color was attributed to preservatives used for prawns.

The pollution provoked a row between Trelew and the neighboring town of Rawson, where RASA (Rawson Ambiental Sociedad Anónima) is based; but Michelou told its residents Trelew had signed an agreement, and effectively accepted the effluents. A Public Works official in Trelew said that was a lie, and "it's ridiculous to minimize this... as if it were normal... they're pouring in untreated liquids, without us knowing."

The original pink color was attributed to preservatives used for prawns. Clarín sought to contact Michelou to find what the red might be, but was told by staff "he's taken a few days off."

RASA in any case stopped dumping its prawn waste into the lake after July - and decided to pour it into the sea instead, which further angered locals. Now it is even less clear why, without the toxic prawn cocktail, the lake has turned violet red.