Environmental chiefs have been left stumped after an iconic Edinburgh waterway changed colour and began smelling of “rotten eggs”.
Local residents were stunned when sections of the Water of Leith appeared to have turned green overnight and began producing a foul odour.
It was originally thought the pungent aroma was caused by a buildup of sulphur in the water or an increase in pollutants below the surface.
However, tests by experts at the Scottish Environmental Protection Agency (SEPA) have yet to reveal any evidence of abnormal chemical levels, leaving the origins of the alien ooze a mystery.
Further examination of the water quality is due to take place on Friday, a SEPA spokesperson confirmed.
Images from the Shore area of Leith show a bright green film appearing just below the surface, turning the water a vibrant green colour.
One local told Edinburgh Live how the water “reminded [him] of his granny’s pea soup” when he walked home from work earlier this week.
He added: “When the sun was hitting it early in the week, the water looked like it was glowing green, it was like something from Alien.
“I’m not sure what is causing it, but the smell is like rotten eggs, it is absolutely revolting.”
Initial tests by SEPA teams showed ‘no evidence of ongoing pollution’.
The agency is now exploring the possibility of algal blooming appearing to change the colour of the water.
Several other bodies of water across the Capital, including the Figgate Pond in Mountcastle, have also been affected by rapid increases in the population of algae.
Further samples are due to be taken over the coming days.
A spokesperson said: “Following our investigations carried out over the 22 and 23 September, we have been unable to identify any evidence of ongoing pollution.
“We are currently investigating the possibility that the green colour and odour is caused by algae.
“Samples will be taken on 24 September to confirm if this is the case."
