The stinking rotting algal bloom that's plagued a Northland east coast beach for many years has returned this summer, prompting some businesses to call for solutions.
Large algal blooms regularly wash up on Waipū Cove, both along the beach and in the river, restricting recreational water use and access to the popular tourist spot in summer.
Waipū Cove Resort manager Dianna Enckevort said the weed bloom - believed to be Spyridia filamentosa - happens every summer, and is particularly bad when storms come in from the east.
It occurs from just past the Surf Lifesaving Club, to the southern end of the beach into the stream, where it becomes trapped, stagnates, and starts to rot and smell.
"It's red and furry and you can see it in the breaking waves," she said.
"When it comes onto the beach and the tide goes out and the sun comes up, it rots and stinks."
Enckevort said the algal blooms can vary according to the weather and tides.
The current one appeared on Waitangi weekend, and it was time locals got together and came up with a solution, she said.
"It's not very nice for guests and tourists.
"When I first came here seven years ago it wasn't here, not for the first couple of years.
"And then it started.
"It's not very pleasant. The smell becomes quite horrid.
"I think something should be done, they've got to identify the weed, and from there what causes the weed."
Over the years Whangārei District Council and Northland Regional Council have received numerous complaints and reports of the algal blooms at Waipū Beach.
There have been similar incidents at nearby Langs Beach, along with Oakura beach north of Helena Bay, and Te Haumi beach near Paihia in the Far North.
In early 2013, after complaints were made to Whangārei District Council about the stench coming from the stream, the council received ongoing resource consent to dredge the river.
The following January, when the algae returned, the river was again dredged.
Camp Waipū Cove manager Anton Trist said the algae was "a nuisance".
It was fortunate it did not appear over the peak summer period from Christmas to early February this year, he said.
"It's not ideal, but it's natural, we can't prevent it from happening.
"Visitors comment from time to time but they're realistic, it's the ocean and it's not just Waipū Cove that's experiencing it.
"There is plenty of usable beach north of the Waipū Cove Surf club for our campers and the Waipū Cove Surf Life Saving Club to have their flags for patrols."
Trist said the algae often moves away naturally, when the wind, swell and current conditions change.
"It will be there one evening and then vanish by the following morning."
In 2017 the Northland Regional Council commissioned a $10,000 NIWA study to shed light on the causes of the algal blooms.
But this was thwarted when only small amounts washed up the following summer, compared to the previous five years.
The project was then reduced in size and modified to include a community questionnaire and analysis of national and international literature on nuisance blooms.
In the revised study, NIWA's Wellington-based Programme Leader Biodiversity Wendy Nelson said it seemed a mix of native, non-harmful species were involved in the Waipū incidents.
The last major deposit happened in the summer of 2015/16 when local farmers helped remove it with tractors and trailers.
At the time an NRC spokesman said nuisance quantities of micro algae and seaweed were common in New Zealand and the algae in Northland was not believed to be dangerous to people or animals.
The Cove café owner Llyod Rooney said the algal bloom has appeared twice in the six years he's owned the café, and comes and goes with the tides.
"Sometimes the tide takes it away. It was here seven days ago and then four days ago it was completely gone, and two days later it's back again.
"It's particularly bad at the moment, it's like walking on carpet."
Rooney said it "would be nice" if the river could be dredged regularly, but he's philosophical about the issue.
"There's not much that can be done about it, apart from removing it when it gets excessive," he said.
"It's not the best. But these things happen, it's naturally occurring. You can't fight nature sometimes."
Northland Regional Council and Whangārei District Council have been approached for comment.