Phytoplankton are microscopic algae that occur naturally in our waterways. The word 'plankton' means 'floating' or 'drifting' describing the free-floating nature of phytoplankton which move with the currents. Phytoplankton are a significant part of waterway ecology as a food source to invertebrates and fish They also oxygenate the water through daytime photosynthesis.
A change in environmental conditions, such as an increase in nutrient levels (usually human induced), a change in temperature or a reduction to flow (see altered flow), can lead to a cell growing very rapidly. A sudden and extreme increase in cell densities is known as a phytoplankton bloom . These events can be detrimental to waterway ecology by reducing the light available to aquatic vegetation (e.g. seagrasses) and can result in fish kills. They can also discolour the water column, present an offensive odour and in some cases cause skin irritation to recreational users of the waterway.
The Department of Health, Department of Water and local government assess and respond to algal blooms, and will provide advice where there is knowledge of harmful blooms (toxin producing) – see algal blooms for more information.
The Phytoplankton Ecology Unit (PEU) of the Water Science Branch undertakes the identification of phytoplankton samples collected around the State by regional staff. Activities of the PEU include:
- algal activity reports for monitored estuaries and rivers
- tracking of harmful algae and bloom occurrences
- coordinating with the Department of Health and Department of Fisheries who issue health alerts relating to harmful algal blooms and fish kills
- developing and managing the algal database AWARE
These activities provide managers with information on the triggers and trends of phytoplankton communities in local and regional waterways. Users also benefit from this information in cases where it may impact their recreational enjoyment of the waterway.