Auckland summer of algal blooms continues

20 December 2002

Auckland Regional Council monitoring has revealed high concentrations of toxic algae in Auckland’s north-eastern beaches once again and the ARC has alerted public health authorities.

The counts for the toxic algae Karenia and Gymnodinium species registered 186,000 at Mahurangi Heads and 132,000 cells per litre at Orewa in the ARC’s monthly monitoring report for December.

The toxic algae are the same species that caused thousands of fish to die at Hatfields Beach in early October. “The levels that we recorded when the fish died in October were between 1 and 11 million cells per litre,” said Mr Grogan.

NIWA scientist Dr Hoe Chang noted in his report to the ARC that it is very likely that these toxic species might take off again at least in the Orewa/Mahurangi area in the next few weeks.

“We’ve sent the results through to the Public Health Biotoxins Unit for use in their public health impacts monitoring programme,” said Pollution Control Manager Eddie Grogan. In previous summers where very high numbers of algae were present, people reported numb lips after swimming.

Mr Grogan urges people who are in the popular holiday coastal area from Leigh to Long Bay to report any dead fish to the ARC’s Water Pollution Hotline. “If you’re heading off to the beach, keep an eye out for dead fish and give us a call if you see any.”

“Fish kill is a good indicator that very high levels of the algae are present. While nothing can be done to prevent fish dying we will respond immediately with more testing and arrange clean-up of the dead fish,” said Mr Grogan. “Our role is to keep an eye on toxic algal levels and to pass the information on to the public health authorities.”

Concentrations of the pink algae Noctiluca, which was non-toxic, highly visible by day and phosphorescent by night, have dropped back to low levels of between 100 and 5000 cells per litre in the December report.

ARC’s 24-hour Water Pollution Hotline number is 09 377 3107.

ENDS

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