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Subtidal low energy over gravel

Short description

Subtidal low energy gravels (including cobbles and pebbles) with or without low density structural macrobiota.

Disclaimer: Ecosystem type descriptions are based on biophysical attributes identified in Central Queensland through expert advice and supported by scientific literature. Not all ecosystem types are mapped based on current inventory, and many of the ecosystems described here may also occur in other parts of Queensland.

Subtidal gravel (low energy). Photo by Maria Zann

Classification categories

Select from the links below to view related ecosystem type categories

Long description

Subtidal low to very low energy gravels (including cobbles and pebbles) with or without low density structural macrobiota. Gravels can be of various Substrate compositions, such as terrigenous (i.e. fragments of decomposed rock or stones washed out of substrates) and carbonate (i.e. coarse shellgrits and coral rubble and fragments).

Biota are highly variable, including very low densities of isolated hard and soft corals, other octocorallians* and sponges, that are insufficiently dense to map as a biota ecosystem.

Carbonate gravels composed of shell or coral rubble are habitats for a variety of invertebrates (e.g. gastropod molluscs including cowries, cones and murexes, or burrowing bivalve molluscs).

*Octocorallia is a subclass of the class Anthozoa in the phylum Cnidaria, and include soft corals, gorgonians, sea whips, sea pens, sea fans and octocorals. Like some of the many other anthozoans, octocorallians are sessile polyp-bearing animals with a mobile larval phase. Octocorallians are distinguished by the eight (i.e. octo) tentacles in each polyp. Most octocorallians do not deposit a rigid calcium carbonate exoskeleton, and therefore tend to attach to reefs rather than contribute to reefal frameworks as per the reef building Scleractinian (hard) corals[1].

Special values

Where biota grows on gravels, these can be biodiverse areas with a wide variety of taxa. Coral rubble areas in and surrounding coral reef lagoons. Mobile crustaceans such as Moreton Bay bugs (Thenus orientalis) occur in deep waters.

Diagnostic attributes:

Inundation 'subtidal'

Benthic depth 'shallow (0-10m)', 'deep (10-30m)', 'very deep (>30m)'

Sediment texture 'Gravel', 'muddy Gravel, 'sandy Gravel', '(muddy) sandy Gravel'


The Naturalness qualifier may be relevant in areas of trawl or dredge fisheries.


Low energy subtidal gravels occur throughout Queensland waters in the nearshore area and on the continental shelf.

The following relates to distribution of this ecosystem type within the Central Queensland mapping area:

  • The western coastline of the Great Sandy Strait where the Elliott Formation geology meets the coast, nodules of iron and aluminium oxide from the duricrust layer form gravel beds subtidally and intertidally
  • Gravel Pits at Dundowran west of Gatakers Bay, Point Vernon, Hervey Bay includes a mixed community of sparse hard corals, soft corals and macro-algae (Asparagopsis) growing on gravels, including cobbles and pebbles of coral rubble and shelly fragments
  • Deep gravelly shellgrit and rubbly areas exist between subtidal dunes west of Rooney’s Point in Hervey Bay are potentially biodiverse areas.


Substrate composition and Morphology are relevant.


  1. ^ Fabricius, K (2010), 'Octocorallia', in Encyclopedia of Modern Coral Reefs, pp. Chapter-35.

Last updated: 11 July 2019

This page should be cited as:

Department of Environment, Science and Innovation, Queensland (2019) Subtidal low energy over gravel, WetlandInfo website, accessed 18 March 2024. Available at:

Queensland Government
WetlandInfo   —   Department of Environment, Science and Innovation