Algal Bloom Monitoring

Algal blooms in the Lower Hawkesbury Estuary, in particular Berowra Creek Estuary, have been a regular occurrence in recent times. Algae are an integral part of the food web in aquatic systems and provide food for higher organisms such as zooplankton. An algal bloom occurs when one particular type (species) of algae grows much more quickly than other species. This can cause discolouration of the water or a reduction in the levels of dissolved oxygen (which can cause fish kills). Some species of algae can also produce toxins that can be harmful to fish, birds and humans.

In order to better manage these blooms, Hornsby Shire Council commissioned Manly Hydraulics Laboratory to install a remote monitoring system that provides an early warning when the chlorophyll-a concentration exceeds 20 µg/L. Once this occurs, Council, on behalf of other estuarine stakeholders, takes action as detailed in the NSW State Government's Algal Contingency Plan. This involves taking samples for laboratory analysis at predetermined locations to determine what species are causing the bloom, whether they are toxic and the extent of the bloom. If the results reveal the presence of toxic species over the guideline thresholds for public health, Council will follow advice from the Metropolitan Algal Coordinating Committee on signage and messaging. For latest information on the presence of harmful algae blooms in the Lower Hawkesbury visit Hornsby Water Quality or call the Water NSW algae hotline 1800 999 457.

Hornsby Shire Council and the Climate Change Cluster (C3) at the University of Technology (Sydney) have developed a decision support tool called Algalert which provides coastal managers with the necessary information to monitor and respond to Harmful Algal Blooms (HABs). To find out specific information about a certain species of harmful algae visit the Algalert website.