Sandy and muddy habitats

The Great Sandy Marine Park includes habitat areas comprised predominately of soft sediment such as sandy shorelines, beaches, exposed sand and mudflats, subtidal sand and mud banks, and intertidal mudflats. These areas provide habitat and pathways between breeding, feeding ground and nursery areas throughout the marine park for species such as shorebirds, turtles, dugong, whales and fish.

Beaches provide habitat for many species in Great Sandy Marine Park and provide connectivity between ocean waters and mainland coastal dune systems, up and down the coastline. Many beach habitats in the marine park are significant nesting beaches for marine turtles.

In low energy environments, soft sediment habitats characterised by silt, clay and mud and fine sand can form. Both soft (muddy) and sandy substrates may support marine plants such as seagrass, algae, mangroves and saltmarsh, however, they are also often bare of vegetation. Often seemingly ‘bare’ soft sediments have microalgae growing between the particles, which can be a food source for important fisheries species. Soft and sandy sediments provide important habitats for polychaete worms, prawns, bivalves, yabbies, mud crabs and fish such as sand whiting, tailor and yellowfin bream. There are also many small animals that live between the sand / sediment particles that provide a food source for other species. Soft sediment areas in the marine park are important areas for yabby pumping, fishing and crabbing.

Some of the important sandy and muddy substrate habitats in the marine park include:

• Sandy Cape – marine turtle courtship and breeding area adjacent to a marine turtle rookery.
• Breaksea Spit – extensive sand spit exposed to the energy of the open ocean. The formation of the spit continues due to the transportation of sand along Australia’s east coast by longshore transport (drift). As the sand travels north it creates shoals and underwater dune fields. North of the marine park this sand disappears over the continental shelf into the deep ocean.
• Hervey Bay – relatively sheltered and low energy sand bottom embayment and foreshore sandy beaches with supporting dune systems.
• Sheltered coastline and estuaries – the sheltered coastline from Burrum River into the Great Sandy Strait has extensive intertidal flats of mud and sand.
• Great Sandy Strait – extensive and dynamic estuarine system which provides habitat and feeding grounds for shorebirds, dugong, turtles, dolphins, fish, molluscs and crustaceans.
• Dayman Spit – a sand spit off Urangan where fish are known to aggregate.
• River systems – includes subtidal sandy bottom channels and intertidal sand flats at river mouths.
• K’gari (Fraser Island) – high energy eastern surf beaches inhabited by fish species targeted by recreational fishers including tailor, dart, bream, whiting and flathead. Several bird species gather on the shore to rest after foraging at sea.
• Rainbow Beach – unique sandy beach and dune system.

Sandy beach, Fraser Island.

Photo credit: © Tourism and Events Queensland