Norfolk

East Anglia scientists find solution to tackle toxic algae

Dead fish Image copyright John Innes Centre
Image caption Fish killed by the toxic algae; Prymnesium in Martham Thurne, Norfolk in 2015

Scientists working on a simple test to detect toxic algae that kills fish say they have found a household solution to prevent it.

Trials in the Norfolk and Suffolk broads showed hydrogen peroxide, used for bleaching hair, is deadly to the golden algae, prymnesium parvum.

The use of the chemical was discovered by researchers working at the John Innes Centre in Norwich and University of East Anglia.

It could prevent fish deaths worldwide.

Prymnesium does not produce obviously visible blooms and is found in slightly salty or brackish water systems like the East Anglia broads.

It can turn water toxic for fish within a matter of days, sometimes even hours and the first indication is often dead or frantic fish.

Image copyright John Innes Centre
Image caption Scientists from the University of East Anglia and the John Innes Centre preparing peroxide solution for field trials

Following an outbreak of toxic prymnesium blooms in 2015, the Environment Agency, supported by angling clubs, rescued almost three quarters of a million fish from Hickling Broad and Somerton.

The fish were released back into safer parts of Norfolk's River Thurne over the course of six weeks in one of the largest rescues of its kind.

Ben Wagstaff, PhD student at the John Innes Centre, said: "We developed a system in the lab where you could use low enough concentrations that would kill algae but wouldn't affect any fish or macro invertebrates.

"Then we took our lab understanding and sprayed a very small section of a broad which had been affected by blooms and it worked brilliantly," he added.

Image copyright John Innes Centre
Image caption Prymnesium trials were carried out at the Whispering Reeds Boatyard in Norwich

Hydrogen peroxide is already used by the Environment Agency during pollution incidents to raise oxygen levels for fish and stop them from effectively suffocating.

Slightly higher doses are needed than for water aeration to kill off prymnesium.

Jamie Fairfull, of the Environment Agency, said: "Prymnesium is one of the biggest risks to the fish population in the Broads.

"Being able to use hydrogen peroxide is a major breakthrough because for us the current options are so labour intensive."

John Currie, general secretary of the Pike Angling Club of Great Britain, welcomed the discovery as a "life-saver".

"At one time before the first Prymnesium wipe out in 1969 this area had the British pike record, so was one of the most important pike fisheries in Europe," he said.

"With this success we hope that in the next six years we will see growth rates coming back to pre-1969 levels, that's completely feasible."

Further trials will now be carried out by the research team to to fully understand how the peroxide mixes and disperses so that it can be used effectively and safely.

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