POOLE Park lake was drained last night following a water test which raised fears over the return of toxic blue/green algae.

Routine quality tests indicated a very low level of an algae which could lead to dangerous blue/green algae, according to a Borough of Poole statement.

Levels were not high enough to cause a risk to public health and the lake was safe to use.

Last night water from the 40-acre saltwater lake was flushed through sluice gates and replaced with seawater from the harbour.

This is a regular maintenance measure, which the council said was not linked to the water test results.

Blue/green algae can produce dangerous toxins that can kill animals and make humans ill.

It has blighted the lake in the past, forcing it to close during four summers in the late 1990s and again in 2003.

Naturally occurring, it is virtually impossible to eliminate but regular flushing of the lake has helped.

Visitors to the park in recent days will have seen that swathes of the lake have turned green thanks to a build-up of tasselweed and green algae – not to be confused with the potentially harmful blue/green algae.

The weed has halted the use of model boats, and affected some sailing activities.

Twelve tonnes of tasselweed were removed from the lakebed earlier in the year, but it has now spread.

At the same time a combination of hot weather and high nutrient levels in the water has seen green algae blooms blanket the surface.

New environmental legislation means it can longer be tackled with chemical treatments – and flushing the lake will not resolve it.

Cllr Peter Adams, cabinet portfolio holder for leisure at the council, said: “We are working as quickly as we can to find a solution that will not pose any risk to wildlife, people using the lake and nearby areas of natural beauty.”