ENVIRONMENTAL experts have used new techniques to remove invasive and potentially harmful plants from the River Colne in Colchester.

The Environment Agency has been working to remove azolla and duck weed from the river near Castle Park after concerns were raised by residents.

Due to prolonged dry weather both this and last year, there has been an increased amount of the weeds, some of which can be harmful to wildlife.


  • All the azolla and duck weed which was removed

The dry weather causes low flows which together with higher temperatures encourage vegetation to grow.

New techniques to remove the weeds and create special refuge areas for fish have been implemented in Colchester for the first time this year.

The refuge areas improve oxygen levels in the water, which fish depend on.

Officers also used a boat and a boom to gather up the duck weed before a digger scooped it out of the water.


  • The river after the work took place

Initial work took place during a week at the end of July, but more is planned for the near future.

Ben Norrington, fisheries officer for East Anglia, said: “We are clearing the surface weed proactively to avoid any incident that could arise from having this vegetation and impact the water quality.

“As temperatures warm up, the surface weed sucks the oxygen out of the water.

“Then we have thunder storms, which lowers the temperature again. High temperature water mixed with low temperature rain can cause an oxygen crash and that’s what will kill the fish.”

The remaining duck weed has been thinned out so the sun and rain will help break it down, boosting the water’s oxygen levels.

In the summer of 2018 more than 1,500 fish died in the River Colne near to Castle Park due to unusually high temperatures.

Colchester’s MP Will Quince has called for Colchester Council, which is responsible for sections of the river, to release a long-term maintenance plan.

The council says a vision document is being drawn up to “protect and enhance the river’s status as a natural and recreational community asset”