WATCH: Pioneering £500,000 water project aims to tip the ecological balance in the Broads
The underwater ecology of two of Norfolk's Broads will be segregated and manipulated as part of a £500,000 project aiming to restore clear water for the first time in more than 50 years.
Norfolk Wildlife Trust (NWT) will create three "biomanipulation" zones at Ranworth and Barton Broads this summer - across an area the size of 15 international rugby pitches - which will be separated from the main body of murky water using more than 1km of floating barriers.
Fish populations inside the zones will be re-balanced by catching and relocating bottom-feeders that can stir up sediment, and other species which devour the algae-grazing daphnia, or water fleas.
By keeping these fish species at balanced levels over large water areas - 10.7ha at Ranworth and 4.2ha at Barton - it is hoped that the algae will clear and water quality will improve, allowing rare water plants such as holly-leaved naiad to flourish.
Meanwhile, the clear water is expected to make fishing easier for birds such as osprey and common tern, which in turn will force fish to hide in plants near the edge for safety, allowing zooplankton to thrive which are crucial grazers of algae.
Some time in the next five to 15 years, the barriers will be lifted. And the NWT hopes the scale of the new zones, allied to the success of past projects at Cockshoot and Barton Broads, will then "tip the balance" to allow clear water to dominate the whole of the Bure and Ant Valleys.
The trust's chief executive Pamela Abbott said: "Today we stand at a tipping point for wetland wildlife in the Norfolk Broads and for once the news is good. Great progress has been made by agriculture and industry to control harmful run-off, and scientists now much better understand the chemical and biological processes which caused and have maintained the dramatic change in water quality in the Broads.
"It is hugely exciting - this has the opportunity to become a really transformative project.
"It is what we did in Cockshoot Broad, and that water now is beautifully clear. So what we are doing is tried and tested and at this scale it has a really good chance of tipping the balance of the whole system into clear water, which we haven't seen here since the 1950s.
"When we eventually lift the barriers we will have this pristine water mixing in with the murky water, but we will have the right combination of fish, daphnia and all the aquatic plants and a really strong population of birds that can keep the populations of fish under control so we will have that beautiful balance that we really want to see returning to the Broads."
Reserve manager Adam Pimble said bream and roach are the two main target species to be removed from the biomanipulation zones.
"They tend to churn up the bottom and do most of the damage on the invertebrates and the plant life," he said. "They will come out and be placed into the Broad or the river system, so we are not taking them away or harming them, we are just taking them out of these exclusion zones.
"Species like pike and perch will stay in as predatory fish, to try and keep the numbers down of the species we don't want."
After the barriers are installed between August and September, the team expects to be able to see the bottom of the Broad beds through crystal clear water within six to eight months.
Water quality, plant regeneration and fish movements will be monitored both inside and outside these fish barriers, to assess their impact across the Broads and their associated dykes.
The Tipping the Balance project partners include the Broads Authority, Natural England, the Environment Agency and ECON Ecological Consultancy. It is funded by Biffa Award's Partnership Scheme, a multi-million pound environment fund, which uses landfill tax credits donated by Biffa Waste Services.
And the Essex and Suffolk Water Branch Out fund has helped pay for new tern rafts, which will be located within the new biomanipulation zones to help boost the tern colonies at Ranworth.