Far North lake unfit for swimming

OUT OF BOUNDS: Swans were enjoying themselves on Lake Waiparera last week, but it's now out of bounds for people and dogs.

Authorities have erected a sign at Waiharara's Lake Waiparera, warning that potentially toxic cyanobacteria in the water may be harmful to people and animals who come into contact with it.

A sign has been erected by the Northland DHB and the Far North District Council, warning against swimming, sailing, water skiing, fishing and drinking the water, noting that any bodily contact could result in skin or eye irritation. Swallowing the water could result in illness, while the internal organs of fish, where toxins could accumulate, should removed before cooking.

Bushland Trust chairman Kevin Matthews said last week that the toxins, which could cause serious health issues for people, would potentially be fatal to dogs.

The Northland Age understands that testing has yet to identify the particular algal bloom responsible for the problem, but Mr Matthews, who earlier last week was critical of authorities' lack of response, said the lake had become "pretty smelly," which would hopefully put people off swimming in it.

The lake's eastern shore was was one of only a handful of approved freedom camping sites in the Far North, which potentially heightened the risk, he added, although the district council's failure to maintain it made it singularly unattractive.

Much of the land around the lake was privately owned or DOC-managed, however, and wasn't fenced.

The lake, Mr Matthews continued, faced a number of major issues, including the high numbers of swans and Canada geese that fed there, defecating in the water and transferring eel grass from Rangaunu Harbour.

"They move between the lake and the harbour," he said, "and oxygen weed is rampant thanks to the high nutrient levels. Changing land use over time has more impact as nutrients head towards lakes, under and over ground, and we can expect more of our lakes to be affected by algal blooms as surrounding land use finally breaks the Aupouri horse's back ... no camels out there that I've seen."

The problem had been exacerbated by the lowering of the lake's outlet (to Rangaunu Harbour) some years ago, which had drained some of the wetlands that had previously served as a buffer, he added.

Only a change in the weather would destroy the bloom, but given the relatively cool weather of recent weeks, and the currently high water table, the current situation did not bode well for summer.

Mr Matthews did not expect the bloom to affect bird life (although he wouldn't eat them), but the inanga and native bullies would not survive if the lake's oxygen level continued to fall, leading to the rotting of plant life.

"The gambuzia will probably be the only survivors," he said.

He had notified the district council some 10 days earlier, but nearby residents had told him that they had been aware of the lake's deterioration for about three weeks.

"People were blaming the butchery [at Waiharara] for the smell, but it was the lake," he said.

"As well as the oxygen problem, vegetation has been rotting because the water level is quite high."

The situation was even more serious given that Waiparera and Ngatu were the only two dune lakes that were still publicly accessible, and it was time for adjacent land owners to give some serious thought as to what they wanted and were prepared to do.

Meanwhile the lake was taking on an increasingly toxic look with every passing day. And Mr Matthews was not impressed with the size or positioning of the warning sign.

"It's A4-size, and hiding under a big macrocarpa tree," he said.

"Not a very effective warning, especially if English is not your first language. You would think the logical place for a water hazard sign would be next to the water."