THE Environment Agency has revealed why a river in York is currently bright green - but says it is nothing to worry about.

The River Foss, which flows through York city centre, currently has a 'thick green blanket' over it, which has been there since the summer.

Press reader Ahmed M raised concerns about the river's colour, fearing the impact it may be having on wildlife.

He said: "Every time I see the river and see the thick carpet of green weed it saddens me.

"I saw birds struggling to feed, they have drowned, no doubt the fish have died, and no one is taking charge."

But officers at the Enviornment Agency told The Press that the cause of the river being green is duckweed - an aquatic plant commonly found in slow-moving waters, such as the Foss.

It forms a blanket-like appearance after tiny round leaves join together on the surface of the water, the agency said.

However, it added that the duckweed posed little risk to the environment.

An Environment Agency spokesperson said: "Duckweed collects on nutrient-rich rivers such as the Foss and during periods of warm, settled and dry weather, its growth can be exacerbated.

"Duck weed is not toxic and its impact to wildlife is normally minimal, but if members of the public see any fish in distress, please report it to our 24 hour incident hotline on 0800 80 70 60.”

City of York Council told The Press that as the river is a natural environment, the likelihood of some plants seeding and weeds forming is inevitable.

The council said it periodically cleans the rivers and their banks, but it is the Environment Agency management team's responsibility to inspect any concerns with environmental damage.