Centre for Marine Futures

Seagrasses form lush meadows that cover the seafloor throughout Geographe Bay in the Dunsborough-to-Busselton region of WA.

These meadows form an important habitat for numerous fish and invertebrate species, utilise nutrients from terrestrial run-off and help to stabilise sand throughout the bay, thus reducing erosion of the shoreline.

Aims

The aim of this work is to set a benchmark of seagrass health and water quality for Geographe Bay so any effect from human population growth on seagrasses can be detected and minimised. Historical information from other studies will also be used to assess the past extent and condition of the seagrass meadows of Geographe Bay.

The questions we are asking are:

• What is the current status of seagrass meadows and water quality in Geographe Bay?
  
• How does this change over time?
• Are elevated levels of nutrients (particularly nitrogen) in the water column of Geographe Bay negatively affecting seagrass meadows?

The project has been designed to compare differences in seagrass meadows and water quality, near to and away from potential point sources of nutrients (drains and rivers), and differing distance from shore and consequently depth.

We have identified more than 70 fish species and more than 80 invertebrate species living in the region. The Leeuwin current is likely to influence the marine biodiversity of the region by bringing warm waters from the north in autumn and winter.

The future

Between 1954 and 1976 seagrass cover declined at some locations in Geographe Bay. Nutrients have also been increasing in the marine system. Future sampling as part of the current project will build a comprehensive picture of the status of seagrass communities in Geographe Bay, including fishes and invertebrates, and whether they change from year to year.

The long-term and effective conservation of these important and fragile marine ecosystems will rely heavily on sound management which in turn relies on sound scientific understanding of the ecology of these systems and the effect of human-induced impacts.