Blue for you

A tributary of the River Frome has turned bright turquoise. The unusual colour change prompted fears of a chemical spill into the river. As of lunchtime today the main River Frome is still flowing clear and has been largely unaffected.
So far the EA (whose picture of the incident is above) have said only this “We are investigating a pollution incident near Frome that has turned a tributary of the River Frome bright blue. There are no reports of wildlife in distress or dead. Samples have been taken for testing. We will continue to monitor the stream over the weekend.”
This comes barely a week since thousands of fish died in the River Sheppey. In that case the cause seemed to be a sudden fall in oxygen levels in the water. The EA are still investigating the incident.
However the River Sheppey flows from Shepton across to the River Brue and so out into the Parrett Estuary.
The River Frome is part of a different water system, flowing north east into the River Avon and so out into the Bristol Channel at Avonmouth.