Habitats and their Dependent Species: Seagrass

Seagrass in port phillip bay

In week seven of our 11-week campaign to celebrate Victoria’s marine environment, we are exploring the fascinating seagrasses of Port Phillip and Western Port Bays, sharing insights from the Victorian State of the Bays (SotB) 2016 report.

Seagrasses are critical to the health of our bays. Unlike seaweeds, seagrasses obtain most of their nutrients from the sediments they grow in and have extensive root systems that help stabilise coastal sediments and reduce erosion, trap sediments (hence improving water quality) and sequester nutrients and carbon in the sediments.

Seagrasses dramatically influencing biodiversity and ecosystem function. Seagrass meadows provide the majority of important habitat within the bays because their three-dimensional structure protects juvenile fish from predators and seagrass plants support algae and invertebrates that are an important food source. The seagrasses around the bays are from the eelgrass species and they act as key ecosystem ‘engineers’ that:

  • stabilise sediments and improve water quality
  • reduce coastal erosion
  • provide nursery habitats and refuge for key fish species, and
  • support algae and invertebrates that provide food for other species.

When the stabilising roots of seagrass are lost, the result is increased turbidity and reduced water clarity. Increased turbidity then kills more seagrass and this process continues in a vicious cycle.

The SotB includes a special case study on Blue Carbon: An environmental powerhouse. Blue carbon is captured by the oceans and along the coasts. Recent global data estimates that vegetated coastal habitats, like those surrounding Port Phillip Bay and in particular Western Port, contribute to 50% of carbon buried in the marine environment.

We invite you to head to our interactive State of the Bays website here and access the SotB 2016 report – the next iteration of the report will include an expanded scope and be titled  the Victorian State of the Marine and Coastal Environment 2021 report - currently in preparation by the Commissioner for Environmental Sustainability.