Algae spread amazes expert

By ANNE BESTON environment reporter

A marine scientist is amazed at the spread of a toxic algal bloom which has closed the North Island's west coast for shellfish gathering, and is creeping up the east coast.

The gymnodinium catenatum bloom forced the closure of the entire North Island west coast when it was discovered in the Manukau Harbour in May.

Since then it has threatened the Marlborough Sounds multimillion-dollar mussel industry, invaded Wellington Harbour and is spreading up the Wairarapa coast.

"It's amazing really that it should travel from one side of the North Island to the other, but we are hopeful the East Cape will form a pretty effective barrier to it spreading further north," said Nelson-based Cawthron Institute marine scientist Lincoln McKenzie. "But then we didn't expect it to get where it is now."

Auckland health protection officer Vanessa Thwaites said Auckland's east coast remained clear.

"Everything is fine. Regular monitoring is being done by the shellfish industry."

MidCentral Health and Choice Health Wairarapa have warned the public against collecting shellfish between Mahia, in northern Hawkes Bay, and Cape Palliser, at the southern tip of the North Island.

Testing showed green-lipped mussels had so far taken in the highest amount of toxin, but other species had been found with risky levels of toxin.

Kina, mussels, toheroa, pipis, tuatua, oysters and cockles from the affected area should not be eaten. Public health protection officer Tony Beachamp said the entrance to Kaipara Harbour had been closed again after being reopened when toxin levels fell. Otherwise the situation remained unchanged.

Eating contaminated shellfish causes paralytic shellfish poisoning, which can be fatal. Symptoms include dizziness, tingling around the mouth and respiratory difficulties.

Mr McKenzie said research suggested the algae was likely to have come from a ship's ballast, discharged into the Manukau Harbour.

"The closest place to New Zealand is Tasmania, where they have had quite major problems with it. It could have arrived under its own steam, but it is quite remarkable it suddenly appeared."