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Seagrass beds

Seagrasses are flowering plants that descended from grasses on the land and moved back into the sea. Seagrasses produce large amounts of oxygen, provide habitat for numerous fish, crabs and shellfish and stabilise the seabed.

This seagrass species Halophila ovalis is known as Dugong Grass. Photo courtesy of Chris RoelfsemaSeagrasses are the primary food source for our threatened dugongs and sea turtles. An adult green turtle eats about two kilograms of seagrass a day while an adult dugong eats about 28 kilograms of seagrass a day. Now that’s a lot of seagrass!

Moreton Bay Marine Park is home to 7 different species of seagrasses which together cover 25,000 ha of deep and shallow water areas. Since 1987, Moreton Bay Marine Park has lost a staggering 20% of seagrasses, which means lost productivity and loss of turtle and dugong food.


Pollution, land clearing and direct damage are the main threats to seagrasses. High nutrient inputs from agricultural and urban run-off cause algae blooms. These blooms shade the seagrass beds, reducing their health and productivity and even killing them completely. Sediments washed into rivers, creeks and down drains flow into Moreton Bay Marine Park and prevent sunlight from reaching seagrasses. Sediments can also smother the seagrasses and the animals that live amongst them.

Moreton Bay’s seagrasses are also under direct threat from land reclamation, boat propellers, boat anchors, trawlers nets and dredging operations for channels, canal estates, airport and port developments.


There are many things you can do to help protect the seagrasses of Moreton Bay:

  • Try and use natural cleaning products in your home (eg bi-carb soda and vinegar) to reduce nutrients and chemicals going into the bay.
  • Take care when anchoring your boat and try to avoid anchoring at areas rich in seagrass.

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