Blue green algae levels are high at Walka Water Works and are increasing at Telarah Lagoon and Rathluba Lagoon.
The high levels have been detected following sampling undertaken this week by Maitland City Council.
Blue green algae are microscopic cells that grow naturally in Australian fresh and saline waters. When conditions are favourable for algae growth, blooms can occur, which can be seen as a thick paint like accumulation on the waters surface or as small green floating dots. Scums are normally green or blue green in colour and have a distinctive earthy smell.
High nutrient levels, slow flow and low wind also encourage the growth of blue green algae.
Executive Manager Planning Environment and Lifestyle Bernie Mortomore says: "Once a bloom has developed, there isn’t a great deal authorities can do to reverse the situation except wait for the favorable growing conditions to dissipate.
"Council will monitor the lagoons at Walka Water Works, Telarah and Rathluba for blue green algae growth over summer as this can be a serious environmental and human health problem, with the release of toxins and skin irritants. Stock and domestic pets are also susceptible to blue green algae toxins."
Blue green algae may cause severe stomach upsets, nausea and skin irritation in both people and animals. Boiling the water does not remove the toxins produced by the algae. If people believe they or their animals have been affected by blue green algae they should seek medical attention.
Council is asking Maitland residents to play a part in reducing the likelihood of a bloom by reducing the amount of nutrients released into local waterways.
Council advises residents to wash their cars on the grass or at a car wash, use a broom not a hose to clear up leaves, clean out gutters regularly, and be responsible with the application of fertilisers.
It is important to report suspected blue green algal blooms in local waterways by phoning 131 555. Up to date information on current algal blooms is available by phoning 1800 999 457.