Chair of the North Coast Regional Algal Coordinating Committee (RACC), David Basso,  said that sampling undertaken on Tuesday confirmed the algae as Trichodesmium, which can cause skin irritation.

He said visual inspections on Wednesday morning indicated that the bloom in the North Haven area had dissipated overnight but reminded residents that blooms can occur quickly and not to enter water bodies where visual scums are present.

The bloom looks like an oil slick on the surface of the water and at the moment the bloom is green grey in colour. In some parts there is foam and it also appears oily or greasy in large patches.

As a precautionary measure NSW Health recommends, due to the obviously high concentrations of algae cells and the potential toxicity of the bloom, that people should avoid contact with the affected water.

Contact with marine blue-green algae affected water can cause skin rashes, asthma and eye and ear irritations.

Mr Bassso added if any health effects are experienced from contact with water affected by algal blooms, medical advice should be promptly sought.

The NSW Department of Primary Industry (DPI) recommends people should not eat recreationally-collected shellfish, pipis, mussels or oysters.

There is some evidence that small quantities of algal toxins may enter fish flesh when a bloom produces toxins.

The DPI also recommends that finfish caught in the area are well cleaned, washed in uncontaminated water,  any internal organs disposed of before consumption and properly cooked.

In time, the bloom will disperse naturally with the winds, currents and tide.