Saltmarshes, seagrasses and algae
The Field guide to common saltmarsh plants of Queensland aims to help people identify the most common species of saltmarsh vegetation within the coastal zone of Queensland.
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Juvenile fish find food and shelter in seagrass meadows.
Fisheries Queensland protects and manages marine fish habitats such as mangrove and other marine plant communities which include saltmarshes, seagrasses, algae and microalgae.
Marine grasses, succulents and algae have a vital role in providing shelter and food for foraging aquatic species such as fish and crabs. They also help hold the soil together, reduce the impact of wind and waves and act as a buffer to nutrients coming from the land.
Saltmarshes are intertidal plant communities dominated by herbs and low shrubs that can tolerate high soil salinity, high temperatures and occasional inundation from salt water.
Saltmarshes play a very important role in providing food for aquatic species and for recycling nutrients. They are home to a diverse range of resident and visiting animals, including fish such as mullet that come in with the tide to eat crab larvae and other prey.
Saltmarsh communities are classified by the type of plants that are dominant and include saltpans, saline grasslands and samphire (succulent) dominated saltmarsh.
Saltmarsh is protected from any unauthorised disturbance. Much of Queensland's important saltmarshes however have already been destroyed, especially near towns and cities where it was seen as 'rubbish' land and filled for industrial and residential development.
Seagrass meadows are found in the shallow coastal waters of every sea in the world and consist of flowering plants that have adapted to grow in the sea but are not actually grasses. Some species have long strap-like leaves typical of grasses, while others have oval or fern-like leaves.
Seagrass habitats vary from a few plants or clumps of a single seagrass species to extensive single or multispecies meadows covering large areas of the seabed. Seagrasses help to stabilise fine sediments with their leaf and root systems and maintain water quality.
Seagrass meadows are highly productive and support many important fisheries by protecting juvenile fish from strong tidal currents and predators. Decaying seagrass leaves break down to provide food for tiny organisms such as flagellates and plankton, which in turn provide food for the juveniles of marine animals such as fish, crabs, prawns and shellfish. Seagrass leaves and roots also provide food for grazing fish, dugong and turtles.
The juveniles of many species of Queensland fish depend on seagrass beds for all or part of their lifecycle, including many popular eating species of fish, prawns and shellfish. Larger predatory animals such as herons, cormorants, sharks, barramundi and salmon are attracted to the seagrass meadows by the schools of bait fish which seek shelter there.
Seagrass meadows are fragile habitats, and activities which damage them may also affect associated fish populations. Excessive pollution from sewage discharge, oil, runoff from the land and physical destruction from dredging, uncontrolled bait digging, boat propellers and anchors can damage or destroy seagrasses.
Marine microalgae are microscopic marine plants (algae) that live in the sea. These tiny plants are extremely important and are the basis of the marine food web on which all species of fish, prawns and shellfish ultimately depend.
Microalgae grow in diverse marine habitats ranging from wave-swept beaches to debris-laden backwater lagoons, estuaries, sand flats, muddy shores, saltmarshes and soft seabeds.
While mudflats and sand flats are often considered to be relatively unproductive compared to fish habitats with seagrass meadows or mangroves, these 'bare' fish habitats support countless millions of tiny microalgae on and below the surface. Together, the mosaic of vegetated and 'bare' fish habitats provides the complete habitat and food requirements for fish and other aquatic animals.
Microalgae directly support diverse communities of small bottom-dwelling animals such as polychaetes, nematode worms, cumaceans, copepods and soldier crabs. Microalgae live within the sediment and form part of the local and regional fish production cycle.
Activities such as dredging, extractive industries, coastal development and tidal fluctuations may impact on microalgae populations which may lead to reduced local and regional fisheries production.