Hard non-branching coral on unconsolidated substrate in very deep water

Long description

Subtidal 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. Hard corals may be of any structural growth form, although often unconsolidated substrates are colonised by non-branching growth forms. Similar to type 94 (undifferentiated coral on unconsolidated substrate in shallow to deep water) except hard coral is confirmed as present and can be split out from a mixed coral ecosystem, and importantly, is starting to create the beginnings of a calcareous framework.

Other biota present include Alcyonarian soft corals and other octocorallians*, sponges, bryozoans, erect calcareous/erect macrophyte algae and turf algae.

Refer to type 70 (undifferentiated corals on unconsolidated) for comments concerning the origin of many Great Barrier Reef fringing reefs on unconsolidated sediments[3].

*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

Coral reefs and communities (including MCEs) are highly valued for their diverse flora and fauna, fish habitat values, and as commercial fisheries. The values of Queensland’s coral reefs are internationally recognised in the World Heritage (Great Barrier Reef) and many MCEs are found within its boundaries. The Outstanding Universal Value of the Great Barrier Reef World Heritage area is based on four criteria (vii), (viii), (ix), (x).

Diagnostic attributes

Inundation 'Subtidal'

Benthic depth 'Very deep (>30m)'

Structural macrobiota 'Hard coral – non-branching'

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

Qualifiers

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

Likely to occur on coral rubble adjacent to an existing deep water mesophotic reef, such as on ridges or slopes adjacent to a reef. Also likely to occur on boulders and gravel, on mud or sand.

Deep water corals are most likely to occur in the lower latitudes. Lower latitude waters tend to have higher light levels than higher latitudes (everything else equal) due to the angle of the light and reduced path length through the water column (P. Muir, pers. comm.). Deep water corals may also occur in shaded microhabitats at higher latitudes, which also indicates the low light tolerance of these corals[2].

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

• This type is unmapped, however depths of greater than 30 metres occur in palaeochannels (e.g. Fitzroy, Mary, Burnett), deep holes and channels of Hervey Bay, the Fraser Canyon and deep continental shelf from Breaksea Spit south.

Comments

Terrain morphology (ridges, peaks etc.) may provide indications of potential areas for mesophotic reef inventory. Consideration of scale is important as these ecosystems may not exist on a seascape scale.

Additional Information

What are Mesophotic Coral Ecosystems? - National Oceanic and Atmospheric Administration

Mesophotic.org

Corals of the World

Mapping the life mesophotic - Marine Biodiversity Hub

References

1. ^ Fabricius, K (2010), 'Octocorallia', in Encyclopedia of Modern Coral Reefs, pp. Chapter-35.
2. ^ Muir, PR, Wallace, CC, Pichon, M & Bongaerts, P (19 December 2018), 'High species richness and lineage diversity of reef corals in the mesophotic zone', Proceedings of the Royal Society B: Biological Sciences. [online], vol. 285, no. 1893, p. 20181987. Available at: http://www.royalsocietypublishing.org/doi/10.1098/rspb.2018.1987 [Accessed 19 March 2019].
3. ^ 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