Algae impacts on estuary health

28 March 2007

A field survey completed by Geoscience Australia has confirmed that microscopic algae can play a critical role in maintaining the health of Australia's estuaries.

The particular type of algae, know as benthic microalagae are single-celled, underwater plants that grow on top of sediment layers in shallow estuary systems up to 2m deep. Data collected from field surveys indicates that the naturally occurring microalgae suppress the growth of water weeds by reducing the levels of available nutrients. This stops water weeds from "choking" the surrounding plant and marine life.

 Bremer Bay

Samples of the water and sediments collected by scientists at various sites along the south-west coast of Australia revealed unexpected low levels of nutrients and weeds in the water, but high concentrations of microalgae at the sediment surface.

Benthic microalgae live in the top level of sediments and feed on the estuary nutrients derived from decaying organic matter. This prevents the nutrients from entering the surrounding water, thus suppressing water weed growth.

Australia's estuary systems are dynamic and delicate ecosystems, and Geoscience Australia is continuing research on a number of projects to help develop a greater understanding of these natural environments. The information is being collated and made available through OzEstuaries, a comprehensive online tool about Australia's estuarine and coastal waters.

Topic contact: Last updated: October 4, 2013