Ngatu facing algal bloom threat

THEN: Lake Ngatu as it was in 1972, when it was so clean the water was blue.

Lake Ngatu, inland from Waipapakauri Ramp, is widely regarded as one of the Far North's environmental jewels, but two local conservationists have warned that it is in big trouble.

Kevin Matthews, from Kaitaia's Bushlands Trust, and Northland Conservation Board member Mike Finlayson, said earlier this week that NIWA monitoring had confirmed what iwi and other concerned community members had been saying for some time; that the lake was very likely to collapse into a major algal bloom this coming summer.

AND NOW: Kevin Matthews with a dead kuta plant. PICTURE/SUPPLIED

After diving in the lake on Saturday, Mr Matthews and Mr Finlayson agreed that the low water level, combined with a thick layer of nutrient-laden sediment, had created the conditions for a dangerous algal bloom.

"That I was able to stand on the sludge with my head out of the water in the middle of the lake shows how shallow it is already, and goodness knows what it's going to look like after a long dry summer," Mr Matthews said.

Just one pair of flippers was enough to kick up the sludge and cloud the water, virtually eliminating visibility, he added. All light-dependent life in the lake would die, and the suspension of nutrients (phosphorous and nitrogen) would provide the food needed for a massive algal bloom, he added, "So it's a double whammy of destruction if that sludge gets stirred up.' Northland Regional Council records showed a steady increase in total nitrogen in the lake since 2013, which now routinely measured well above the national bottom line of 0.75g per cubic metre.

The situation was also alarming Te Runanga o Ngai Takoto's environmental manager, Kaio Hooper, who was photographing dead fish and kuta and the sediment and invasive weeds that were coming up from the bottom.

"It's time the community got more on board with the threats to the lake and how we can collectively do our best to protect it," he said.

"As a bare minimum it should be safe for kids to swim in it, now and in the future."

Mr Matthews and Mr Finlayson supported his calls for an urgent meeting.

"NIWA has now confirmed what local iwi and other environmentalists were saying, adding impetus to the urgency of this meeting," Mr Finlayson said, noting that concerns had been raised some weeks earlier, when the conservation board visited the lake. He had wanted to return to "get to the bottom of this."

The meeting, at 10am on Saturday week (November 28) at the southern end of the lake, would be open to everyone, especially lake users, hapu, locals and others with environmental concerns, Mr Hooper said.

"We believe it is still possible to keep Lake Ngatu's water to a recreational standard, but for this to happen will require a plan of action to reverse the current steady decline. This is going to take a considerable effort by all the community, and this meeting will be the first step to not only retaining recreational use but hopefully improving the overall health of this lake.

"This is about the mana o te wai."