Saltmarsh, seagrass and algae

Saltmarshes

Saltmarshes are intertidal plant communities, dominated by herbs and low shrubs that can tolerate:

• high soil salinity
• high temperatures
• occasional inundation from salt water.

Saltmarsh communities are classified by the type of plants that are dominant, such as:

• saltpans
• saline grasslands
• samphires (succulents).

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 animals (such as mud crabs) and visiting juvenile and adult fish species (such as bream, whiting, mullet) that come in with the tide to feed or seek shelter from predators.

Use the Field guide to common saltmarsh plants of Queensland to identify the most common species of saltmarsh vegetation within the coastal zone of Queensland.

Seagrasses

Seagrasses are flowering plants that have adapted to grow in the sea but are not actually grasses. Seagrass habitats vary from a few plants or clumps of a single species, to single or multi species meadows that cover large areas of the seabed, in every sea in the world.

Some species have long strap-like leaves typical of grasses, while others have oval or fern-like leaves. Seagrass leaf and root systems:

• help to stabilise fine sediments and maintain water quality
• provide food for grazing fish, dugong and turtles.

Seagrass meadows are highly productive fish habitats and support juveniles of many of Queensland's popular eating species of fish, prawns and shellfish. These intertidal and subtidal marine plants are part of the fish habitat mosaic, supporting the feeding, nursery and shelter lifecycle requirements of fish and other animals.

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 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.

The non-profit Seagrass-Watch Global Seagrass Observing Network monitors the status and trends in seagrass condition.

Marine algae

Macroalgae are a direct food source for grazing fish (such as luderick and rabbitfish) and provide shelter and nursey habitats for fish and invertebrates.

Marine algae can grow:

• in shallow tidal zones
• with mangroves and seagrasses
• as tufts on rocky shores
• by encrusting rocky outcrops.

Marine algae are extremely important for primary production, supporting the coastal food chain and as a major food source for important forage species.

Activities that may impact marine algae populations include invasive works such as:

• dredging
• extractive industries
• coastal development
• tidal fluctuations.