Hard branching coral on unconsolidated substrate in shallow to deep water

Long description

Subtidal 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. This ecosystem resembles undifferentiated coral on unconsolidated substrate in shallow to deep water (type 94), except that it is a branching form starting to create the beginnings of a calcareous framework, and branching corals create a significant framework for fringing reefs[7]. Depending on whether branching corals, non-branching hard corals or octocorallians* are dominant, this ecosystem may switch back and forth between types 86 (non-branching on unconsolidated), 94 (undifferentiated coral on unconsolidated) and 70 (hard undifferentiated on unconsolidated) and not be a distinct ecosystem in itself.

Coral rubble and corals on unconsolidated substrates can be cemented together by crustose coralline algae (see type 58), preventing it from being swept away by storms and cyclones[2]

Refer to type 70 (undifferentiated corals on unconsolidated) for comments concerning the origin of many Great Barrier Reef fringing reefs on unconsolidated sediments[7].

*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[4].

Special values

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.

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 rugose shelter 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).

Diagnostic attributes

Inundation 'Subtidal'

Benthic depth 'Shallow (0-10m)', 'Deep (10-30m)'

Structural macrobiota 'Hard coral – branching'

Consolidation 'Unconsolidated', 'Intermediate', 'Unknown'

Qualifiers

The Cover qualifier is relevant to any coral ecosystem as live coral percentage cover is an essential indicator used in coral monitoring. See monitoring links in type 90. 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.

Distribution

Potentially found in clearer waters with sand and rubble shoals where coral growth could potentially ‘turn-on’.

Branching corals such as Acropora spp. tend to be sensitive to water clarity and other attributes associated with water quality (nutrients, sedimentation and suspended solids) which can deter coral larvae (planula) from settling and disrupt or smother newly settled corals. Generally there will be more settlement of branching corals where there is a good supply of planktonic larvae and understanding the source of the larvae and how the currents disperse them is important[3].

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

• A patch of branching corals grows on the rocky shore boulder coastline of the Woongarra coast off Bundaberg[1] where the water is comparatively clear and receives medium wave energy. Shoals and similar ridge-like Terrain morphology north of Curtis Island to the Keppels are likely to be colonised by branching corals.

Comments

Relevant other attributes include Water clarity and Energy magnitude. Branching corals can tolerate a degree of wave action, although on unconsolidated substrates this may lead to dislodgement. Benthic rugosity of coral reefs, particularly branching corals, is important for creating three-dimensional living space for biota including fish, and allowing more shading which can protect corals during bleaching events[6].

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[5].

Additional Information

Protecting the Great Barrier Reef - Queensland Government

Coral - Department of Environment, Science and Innovation

Coral reefs - Queensland Museum

The Reef - Great Barrier Reef Marine Park Authority

Corals of the World

Great Barrier Reef - UNESCO

Nationally (DIWA) and internationally important (Ramsar) wetlands - WetlandInfo

Coral Indicators for the 2017 Gladstone Harbour Report Card - Australian Institute of Marine Science

Reef Report Card 2016 - Queensland Government

Great Barrier Reef Outlook Report - Great Barrier Reef Marine Park Authority

Monitoring inshore reefs - Australian Institute of Marine Science

Reef Check Methods - Reef Check Australia

Coral reefs - Museum of Tropical Queensland

Remote Sensing Research Centre - The University of Queensland

References

1. ^ Bushell, HL (2008), Assessment of the status of the benthic reef communities within the Woongarra region. Unpublished third year undergraduate report, , School of Environmental Science and Management, Southern Cross University, Lismore, NSW 2480.
2. ^ CSIRO (2018), eReefs CSIRO Hydrodynamic model (Temperature, Salinity, Wind, Current) Summaries (AIMS). [online] Available at: https://eatlas.org.au/data/uuid/375c9dc9-70f8-4d97-a3e9-c013896a81e5 [Accessed 5 April 2019].
3. ^ Davidson, J, Thompson, A, Logan, M & Schaffelke, B (30 January 2019), 'High spatio-temporal variability in Acroporidae settlement to inshore reefs of the Great Barrier Reef', PLOS ONE. [online], vol. 14, no. 1, p. e0209771, ed. C Linares. Available at: http://dx.plos.org/10.1371/journal.pone.0209771 [Accessed 22 March 2019].
4. ^ Fabricius, K (2010), 'Octocorallia', in Encyclopedia of Modern Coral Reefs, pp. Chapter-35.
5. ^ Hoegh-Guldberg, O (1999), 'Climate change, coral bleaching and the future of the world's coral reefs', Marine and Freshwater Research. [online], vol. 50, no. 8, p. 839. Available at: http://www.publish.csiro.au/?paper=MF99078 [Accessed 11 June 2019].
6. ^ Muir, P, Wallace, C, Bridge, TCL & Bongaerts, P (25 February 2015), 'Diverse Staghorn Coral Fauna on the Mesophotic Reefs of North-East Australia', PLOS ONE. [online], vol. 10, no. 2, p. e0117933, ed. S C A Ferse. Available at: http://dx.plos.org/10.1371/journal.pone.0117933 [Accessed 19 March 2019].
7. ^ a b Smithers, SG, Hopley, D & Parnell, KE (2006), 'Fringing and nearshore coral reefs of the Great Barrier Reef: episodic Holocene development and future prospects', Journal of Coastal Research, pp. 175-187.

Last updated: 12 July 2019