Non-calcareous consolidated or intermediate substrate

Long description

Subtidal consolidated or intermediate substrates of terrigenous (land-based) origin where biota extent is unsurveyed. The Lithology or rock type may influence the shape, chemistry and nature of the biota growing on these ecosystems. These ecosystems include:

1. The subtidal reefal areas below rocky shores and boulders.
2. Isolated subtidal rocky reefs that are not an integral part of an intertidal rocky system
3. Coffee rock, a soft, dark-brown coloured friable rock consisting of sand grains weakly cemented together by organic matter (mostly plant-based) (see type 25 for further information). Intermediate (coffee rock) ecosystems, which vary considerably in the colonising biota. Potentially coffee rock reefs need investigation regarding whether they are groundwater dependent ecosystems or wonky holes[3].

This ecosystem type also includes those where naturalness is modified (i.e. artificial structures made of concrete[1]). These ecosystem types do not support as diverse a fish fauna as natural reefs.

Special values

Terrigenous subtidal rocky reefs are important fish habitats, as are coffee rock ecosystems as they provide staging posts for fish, existing in areas largely devoid of structure and surrounded by unconsolidated ecosystems.

Grey nurse sharks are an endangered species (Environment Protection and Biodiversity Conservation Act (EPBC)-listed) associated with deep rocky reefs.

Depending on depth, a variety of coral reef fish may be present, such as mangrove jack etc. Other tropical coral reef snappers occur in deep to very deep waters (e.g. red emperor, scarlet sea perch, crimson sea perch). Pearl perch occur on the very deep reefs in subtropical waters. Coffee rock reefs are habitat to slatey bream, seasonal coral trout and wrasses, and grass sweetlip.

Rocky reefs and coffee reefs which are submerged below depths of 10m or more usually provide habitat for pelagic fish in the water column above them[4].

These ecosystems may contain unmapped coral (see the contains attribute field for the keyword ‘coral’). Where coral is directly growing on rock and biota is unsurveyed, the terrigenous subtidal rocky reefs may also be coral communities[5] (see figure in type 100).

Rocky reefs may include erect macrophytic algae, see type 55.

Coffee rock reefs may include reefal gardens, refer to types 98 and 117.

Diagnostic attributes

Inundation 'Subtidal'

Consolidation 'Consolidated', 'Intermediate'

Substrate composition 'Terrigenous' (i.e. land based)

Qualifiers

Can also include modified ecosystem types such as subtidal parts of boat ramps, jetties and port infrastructure. The biota growing on these ecosystems would be very different from that growing on natural rocky or coffee rock ecosystems[2][1].

Distribution

Subtidal rocky reefs are found throughout Queensland, generally occurring as outcrops of terrestrial and intertidal geological formations. Subtidal coffee rock reefs are more prevalent in the lee of large sand systems in southern Queensland from Fraser Island southward.

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

• Rocky reefs occurring off Double Island Point include Wolf Rock and the Pinnacles (habitat for grey nurse shark).
• Intermediate (coffee rock) ecosystems are found subtidally on the inside of Fraser Island within Hervey Bay and the Great Sandy Strait. These ecosystems vary considerably in the biota that can colonise them as in areas such as the northern Great Sandy Strait and south-eastern Hervey Bay they are alternately sand submerged and exposed. Other locations include Seary’s Ledge in Tin Can Bay, coffee rock along western shore of Fraser Island and the Great Sandy Strait adjacent to high sand dune cliffs (indurated deep soils, giant podsols).
• Selected coffee rock reefs were mapped from sidescan sonar by Queensland Parks and Wildlife Service (unpublished, 2010) and additional information on their values was provided by the University of the Sunshine Coast. Detailed mapping of the Seary’s Ledge coffee rock reef was possible based on the Cooloola Coastcare’s CUBA project (see video). Other coffee rock ecosystems of the Great Sandy Strait were validated by ReefCheck (see here).
• The Lithology or rock type may influence the shape, chemistry and nature of the biota growing on these ecosystems. The subtidal rounded boulders and decomposed granite around Rodds Peninsula will differ from that of the Agnes Water volcanics and Woongarra coastal basaltic communities. Potentially the rocky reef ecosystems have a suite of algae, coral and other encrusting fauna (octocorallians).
• Artificial structures include concrete boat ramps occurring throughout the mapping area, especially close to areas of human habitation. Mapped structures also include concrete jetties and wharves (e.g. in Gladstone Harbour). These structures have 'modified' naturalness.

Comments

Intermediate substrates mapped to date are coffee rock. Extent comments for type 100 (calcareous consolidated or intermediate) also apply to the extent of this type (i.e. these ecosystems require better bathymetry inventory and biota inventory to confirm the extent of coral or other biota).

Additional Information

Great Sandy Strait Marine Park Regional Profile: Offshore region - Department of Environment, Science and Innovation

References

1. ^ a b Henderson, CJ, Gilby, BL, Schlacher, TA, Connolly, RM, Sheaves, M, Flint, N, Borland, HP, Olds, AD & Handling editor: Henn Ojaveer (4 February 2019), 'Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes', ICES Journal of Marine Science. [online] Available at: https://academic.oup.com/icesjms/advance-article/doi/10.1093/icesjms/fsz007/5306605 [Accessed 13 June 2019].
2. ^ Malerba, ME, White, CR & Marshall, DJ (2 July 2019), 'The outsized trophic footprint of marine urbanization', Frontiers in Ecology and the Environment. [online], p. fee.2074. Available at: https://onlinelibrary.wiley.com/doi/abs/10.1002/fee.2074 [Accessed 22 July 2019].
3. ^ Stieglitz, T (2005), 'Submarine groundwater discharge into the near-shore zone of the Great Barrier Reef, Australia', Marine pollution bulletin, vol. 51, no. 1, pp. 51-59, Elsevier.
4. ^ Submerged pinnacles and small seamounts; deep, different and diverse coral reefs. IN Australian Coral Reef Society 92nd conference and AGM program, Tangalooma resort, moreton island Qld 7-9 May (2019), ed. G Cresswell.
5. ^ Van Woesik, R & Done, TJ (1997), 'Coral communities and reef growth in the southern Great Barrier Reef', Coral Reefs, vol. 16, no. 2, pp. 103-115, Springer.

Last updated: 22 July 2019