A prominent scientist says rotting, putrid algae on Waipu Cove beach needs to be cleaned up before it wipes out local beach-dwelling marine life.
The Northland Regional Council is reluctant to move the algae, saying it is not a health risk and nature should be left to do its own thing.
However, Floor Anthoni, marine ecologist and director of Warkworth-based Seafriends marine conservation and education centre, says the algae drifting into the adjacent river and rotting is poisonous to river-dwelling eels and freshwater life.
Dr Anthoni said algal blooms and seaweed growth had been greatly exacerbated by the dumping of fertiliser and human waste in the ocean.
"It now lies rotting away on the beach and in the shallows - an entirely unnatural situation," he said.
Last week Waipu Cove beach was carpeted in algae for the second time in three months. It has started to rot, releasing a putrid stench - adding to the stink coming from the nearby stream, which contains rotting algae that hit the beach last December.
While the Whangarei District Council has planned to start dredging the river - which is black with the rotting sediment - the regional council is taking a "let nature take its course" approach to the algae on the actual beach shore.
Regional council consents and monitoring senior programme manager Colin Dall said the smell could be unpleasant: "However, sometimes mother nature needs to be left alone to do her thing."
Dr Anthoni did not agree, given the number of people on the beach and the amount of fertiliser and human waste fuelling algae growth in the ocean.
"We have too much people - there is nothing natural about that," he said. "Before the algae stinks, it is food for beach slaters - once it starts to stink, it's poisonous to beach life and sea life even if it washes back out to sea."
Dr Anthoni was consulted by the original Auckland City Council in determining that Auckland's North Shore beaches should be groomed. Auckland Council manager local and sports parks Mark Bowater said beach grooming was done on a number of Auckland's beaches.
Dr Anthoni said in the case of Waipu Cove, using a beach groomer would not be enough. "You'd need diggers".
"In Ireland, where they are having the same sort of problem, they are using bulldozers. It needs to be taken off the beach and buried, and deep, as it is toxic," he said.
The district council's waste and drainage manager, Andrew Carvell, said it was set to dredge the river to remove the sand that blocked the entrance, trapping algae that then started to rot.