Canoe Lake clear up underway after heatwave causes an 'explosion' of algae blooms

Works are underway to clear an ‘explosion’ of algae which has plagued Canoe Lake as a result of the heatwave.

Huge algae blooms have covered much of the lake’s surface in recent weeks causing local concern, coupled with a delay in beginning the cleaning after a breakdown of the specialist craft which is used to float around the lake to cut and scoop up all of the algae.

It was waiting for a much-needed part to arrive from Holland, but yesterday (July 9) work finally began with residents already beginning to notice a difference at the popular attraction in Southsea.

Sean Moth from Harbour Clean said: “It’s just the hot weather, nitrates in the water and the water levels just make this stuff explode. It is the same all over the country at the moment, all ponds are very similar to this.

“(Portsmouth City Council) were getting us in at the right time - until we has the breakdown of the machine and we were waiting for the parts. So that got us here a little later than we usually would.”

As previously reported by The News, algae thrive in hot, sunny conditions because higher water temperatures speed up metabolic processes inside algae cells, while increased sunlight boosts photosynthesis. Excess nutrients, including nitrogen and phosphorus, can also contribute to algal growth.

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“There’s areas out there which are really thick, and there’s areas out there which are really thin,” Mr Moth explained.

“Because the water levels are low here we are running on mud most of the time so the machine is not floating. And because of the tracks, they are like caterpillar tracks but they have got paddles on, they can get stuck in the mud. So you can't turn on the spot like you would a normal digger.”

The experienced marine waste control company, which also looks after a number of other ponds in the area, has said that the heatwave made the clear-up operation ‘more challenging’, with Canoe Lake effectively ‘fed by the sea’ which is also filled with algae.

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“The works normally take two or three days,” Mr Moth said. “but it all depends on the growing conditions.

“Obviously at the moment it is heatwave after heat wave so it is ideal growing conditions and the water temperature it high.”

Opened in 1886, Canoe Lake was created by draining marshland that once covered much of Southsea. Originally designed for model yacht sailing, the seawater-fed lake went on to become a popular community attraction, known for pedalos and swans.

Cllr Steve Pitt, Leader of Portsmouth City Council said: "We know many residents have been concerned about the build-up of algae at Canoe Lake and we're pleased that clearance work is now under way. Our contractor, Harbour Clean, began work this week following a short delay while its specialist amphibious vehicle was being repaired.

"The algae is being carefully removed using specialist equipment and placed at the edge of the lake to drain naturally. This gives fish, insects and other wildlife the chance to safely return to the water before the material is collected and taken away for recycling. Work will continue throughout the rest of the week, and we thank residents for their patience while this takes place."

Algae and the recent hot temperatures has also created other issues across the area, including at both Baffins Pond in Portsmouth and at Stoke Lake in Gosport where dead fish have been found.

Following a visit, the Environment Agency said that the deaths were likely due to a lack of oxygen in the water combined with algal growth.

Portsmouth City Council has been approached for comment.