Hard non-branching coral on unconsolidated substrate in shallow to deep water
Subtidal coral ecosystems in shallow to deep water on unconsolidated substrates, dominated by non-branching hard corals.
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 non-branching hard corals in shallow (0 to 10 metres) to deep water (10 to 30 metres) on unconsolidated or intermediate substrates including boulder, gravel (i.e. cobble and pebble), sand, mud and/or coffee rock. Non-branching corals include massive, submassive, plate/table, bushy, vase/foliose or encrusting growth forms. Growth forms of coral are influenced by biophysical factors including depth, light and currents. Generally, non-branching corals tolerate more turbid waters than branching corals. Non-branching coral ecosystems can have high species diversity, particularly within the subtropics where both tropical and temperate species co-occur at the limit of their range.
Many substantial Great Barrier Reef fringing reefs originally began thousands of years ago by hard corals colonising unconsolidated substrates such as clay (mud)/sand (e.g. Dunk Island, Great Palm Island) or gravel/boulder. Similar rubbly coral areas exist today. The difference between these communities and those on consolidated substrate is that they are vulnerable to mechanical movement (e.g. wave action throwing unconsolidated particles up onto the shores, and may never become permanently established (Smithers pers. comm.)).
This ecosystem resembles undifferentiated coral on unconsolidated substrate in shallow to deep water (type 94), except that it is a non-branching form starting to create the beginnings of a calcareous framework. Depending on whether branching corals, hard corals or octocorallians* are dominant, this ecosystem may switch back and forth between type 78 (branching coral on unconsolidated), 94 (undifferentiated coral on unconsolidated) and 70 (hard undifferentiated coral on unconsolidated) and not be a distinct ecosystem in itself.
*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.
The values of Queensland’s coral reefs are internationally recognised in the World Heritage and Ramsar conventions. The Outstanding Universal Value of the Great Barrier Reef World Heritage area is based on four criteria (vii), (viii), (ix), (x). The Ramsar convention also includes coral reefs as one of its wetland types which make up part of a site’s ecological character (a combination of the ecosystem components, processes and services of the wetland). The Great Sandy Strait Ramsar wetland also includes coral reefs (e.g. Woody and Round Island reefs, coral communities at Little Woody Island, and soft corals on coffee rock reefs). Shoalwater and Corio Bays Ramsar wetland and the Moreton Bay Ramsar wetland also includes fringing coral reefs.
Non-branching hard corals growing on unconsolidated substrates provide the beginnings of calcareous reefal framework at a finer scale, providing structure for the attachment of other flora and fauna (e.g. sponges, other invertebrates, macroalgae etc.) and providing nooks and crannies and food for corallivorous fish (e.g. angelfish) or algal farmers such as damselfish. Corally, gravelly, rubbly substrates can be productive areas for gastropod molluscs (e.g. cowries, cones and murex).
Benthic depth 'Shallow (0-10m)', 'Deep (10-30m)'
Structural macrobiota 'Hard coral – non-branching'
Consolidation 'Unconsolidated', 'Intermediate', 'Unknown'
Potentially Naturalness qualifiers are relevant. Being able to be shifted by mechanical action means that these ecosystems can be potentially modified by trawling or dredging.
Period and Trend qualifiers are relevant as wave action from storms or cyclones can move these colonies about on the sea floor, or waves can deposit them in the intertidal area (see Energy source and magnitude).
Potentially non-branching corals may occur on unconsolidated substrate in the proximity of consolidated coral ecosystems on the inner shelf.
The following relates to distribution of this ecosystem type within the Central Queensland mapping area:
Inventory on gravelly substrates may expand the distribution of this ecosystem type. Consideration of scale is important as these ecosystems may not exist at a seascape scale. This ecosystem type can be part of a succession on unconsolidated substrate, ultimately leading to consolidated calcareous reef (i.e. types 70 (undifferentiated coral on unconsolidated), 94 undifferentiated coral on unconsolidated), 86 (non-branching hard on unconsolidated), 98 (soft coral reefal gardens on unconsolidated), and then to consolidated types 90 (undifferentiated coral), 82 (non-branching hard), 74 (branching hard) etc.).
Water temperature is critical to all corals as they are sensitive to extremes of heat and cold, resulting in bleaching due to the loss of endosymbiotic dinoflagellates (e.g. zooxanthellae) and therefore the ability to photosynthesise.
Last updated: 12 July 2019
This page should be cited as:
Department of Environment and Science, Queensland (2019) Hard non-branching coral on unconsolidated substrate in shallow to deep water, WetlandInfo website, accessed 13 April 2023. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/ecology/aquatic-ecosystems-natural/estuarine-marine/descriptions/86/