Lake Rotokare is again out of bounds to swimmers and boaties due to a toxic algal bloom.
South Taranaki District Council environmental health officer Doug Scott said the lake would be closed until cleared by the Taranaki District Health Board.
He said contact with poisonous algae may cause irritation of the skin, eyes and throat, and could also bring on asthma.
Earlier this year, a team of experts from Waikato University hypothesised growing numbers of perch may be responsible for the algae plaguing the reserve.
Perch were introduced as a sports fish species.
Sanctuary manager Simon Collins said while it was unfortunate the lake was again out of action, they were working with the university to discuss options for fewer or shorter closure periods.
He said the reserve grounds remained open.
The blue-green algae, also known as cyanobacteria, tends to form in fine weather, on the rocks of river beds when the water is relatively calm.
Any visitors to the reserve showing symptoms should consult their doctor immediately or contact the health board Health Protection Unit on 06 753 7798.
- © Fairfax NZ News
How much would you pay for a seat on the coastal walkway?