Intertidal coral

Long description

Intertidal hard and/or soft coral community growing on any type of substrate (i.e. unassigned), typically consolidated substrates of carbonate platform, rock base, pavement or boulders but also intermediate (coffee rock) and unconsolidated. Includes fringing true coral reef on carbonate platform and fringing coral communities on either rocky base, pavement or boulders, and in intertidal rock pools. Typically dominated by hard corals such as Acropora spp., Pocillopora spp. and favids, and/or soft corals from the genera Sarcophyton, Sinularia and Lobophyllia. Encrusting algae, such as crustose coralline algae (CCA), may grow on bare areas between the coral. Also includes soft coral, or mixed coral gardens where they occur intertidally within seagrass meadows.

Sea levels control the level to which coral growth can occur, with corals either growing to the surface or becoming submerged in response to changing sea levels. Well-developed, fringing reefs have a reef flat with corals that are growing close to the surface and are limited by tidal inundation[16]. Intertidal corals usually occur well below mean sea level, where they are only emergent during spring tides, and occasionally in tidal pools higher up the shore. Refer to type (100) for a diagram comparing well-developed fringing reefs with submerged reefs and rock with coral growth[16].

Intertidal branching hard corals often experience some wave action and can disperse vegetatively where pieces are broken off by a storm. Generally, branching corals are indicative of slightly clearer waters. Species diversity of the genus Acropora is highest in north Queensland and on the offshore reefs of the Great Barrier Reef, and also on coral rocky communities of the East Australian Current further south. Inner shelf and fringing reefs have a lower species diversity, especially towards their range limits where high latitude specialists, such as Acropora bushyensis occur[8]. Some shallow water Acropora spp. are depth generalists, also found in mesophotic coral ecosystems (MCEs. i.e. low light coral ecosystems).

Intertidal non-branching hard 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, current etc.[7]. Non-branching coral ecosystems can be quite high in species diversity, within the subtropics including both tropical and temperate species at the limit of their range[4]. Non-branching corals of inshore waters can also be significant reef-builders. Massive corals can live for hundreds of years and grow to several metres in diameter. Generally, non-branching corals tolerate more turbid waters than branching corals, with the Dendrophyllidae and Faviidae families typically tolerating the low light and high nutrient conditions experienced on nearshore fringing reefs. Turbid water specialists of the inner Great Barrier Reef are capable of rapid growth, forming monospecific stands of many hectares, including foliose, cabbage-like Turbinaria spp. corals and the flower-like submassive Goniopora spp. whose polyps are emergent in the daytime and are often mistaken for soft corals[5][3][17]. Both genera are heterotrophic, i.e. capturing planktonic prey as an alternative to photosynthesis, a distinct advantage in turbid waters[2]. Massive brain corals (Merulinidae, formerly Favidae) are characteristic of Moreton Bay coral communities growing on rocky substrate and on old limestone reefs, but do not form significant reefs today[10][13].

Intertidal soft coral biota includes Alcyonarian soft corals (e.g. Cladiella, Klyxum, Sinularia, Lobophytum, Sarcophyton and Dendronephthya spp.) and other octocorallians* which can be subdominant with other taxa include sponges, zoanthids, ascidians and hydroids. Alcyonarian soft corals will grow on the more persistent coffee rock substrates that are alternately covered over by sediments and exposed, and are more likely to have biota typical of reefal gardens (Andrew Olds, 2018, pers comm.). Some soft corals possess endosymbiotic dinoflagellates (e.g. zooxanthellae) and can photosynthesise, these will often be found in shallower water (e.g. families Nephtheidae, Alcyoniidae and Xeniidae).

*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[9].

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. Shoalwater and Corio Bays Ramsar wetland and the Moreton Bay Ramsar Wetland also includes fringing coral reefs.

Intertidal corals are habitats for coral reef fish including butterflyfish and damselfish, which inhabit tidal pools. On the incoming tide roaming predators such as coral trout and slatey bream, (Diagramma picta) and roaming herbivorous fish, such as rabbitfish (Siganidae) and parrotfish swim over the inundated intertidal corals searching for food. The grazing fish are important for maintaining the balance between algae and corals, as is maintaining a natural balance between predators and grazers[14].

Intertidal corals are highly accessible and their coral, fish and mollusc species may be targeted by aquarium collectors. At high tide the roaming predatory fish may be targeted by spear-fishermen and anglers.

Diagnostic attributes

Inundation 'Intertidal – Lower low', 'Intertidal – Mid low', 'Intertidal – Upper low', 'Intertidal – Low undifferentiated', 'Intertidal – Lower medium', 'Intertidal – Upper-medium', 'Intertidal – Medium undifferentiated', 'Intertidal – High', 'Intertidal – Undifferentiated', 'Intertidal – High undifferentiated', although usually found between lower low and lowest astronomical tide.

Structural macrobiota 'Hard coral – undifferentiated', 'Hard coral – branching', 'Hard coral – bushy', 'Hard coral – massive', 'Hard coral – submassive', 'Hard coral – vase/foliose', 'Hard coral – plate/table', 'Hard coral – encrusting', 'Hard coral – mixture of structures', 'Hard/soft coral – undifferentiated' and 'Soft coral - octocorallians'

Qualifiers

Qualifiers are unmapped, although temporally variable in Period and Trend in response to flood events where impacted by flood plumes, and algae may become dominant immediately post-flood[6][7]. Freshwater from flood plumes is known to float on salt water and the surface two metres can be killed by freshwater in a flood event[12].

Distribution

Areas with coral growing intertidally are usually regarded as true fringing reefs, depending on the width of the area from the reef edge to the mainland, and the depth to which coral has grown[16]. ‘Well developed fringing reefs’ occur where intertidal corals and associated sedimentation has grown to the surface, and the width of the area is between 50 and 200 metres, a ‘coral community’ occurs where coral directly grows on a consolidated substrate in shallow water and ‘incipient reef’ occurs where coral is accumulating sediment and its own reef in shallow water but has not yet grown to the surface. The majority of fringing reefs of the coastal Great Barrier Reef began their growth on unconsolidated sediments and few originated on rock[15]. For further discussion on the different types of fringing reef, see type 100 (consolidated/intermediate calcareous reef – including coral platform).

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

• Previously 22 degrees south was regarded as the southern limit of true fringing reefs, however intertidal corals at Hervey Bay and Pancake Creek meet the definition of true ‘fringing reefs’. Hervey Bay reefs include the largest Turbinaria reefs in central Queensland south of Shoalwater Bay, large Acropora branching coral colonies, and range limits of tropical and subtropical corals[8][17]. Pancake Creek includes a large Acropora branching coral reef within an estuary. Woongarra coast intertidal corals are mainly soft corals occurring on consolidated substrate[11][1], meeting the definition of ‘coral communities’[16]. Intertidal corals occur higher on the rocky shore rock pools just below mean sea level at Mon Repos.
• On consolidated substrates in the Central Queensland mapping area, bands of turf algae and zoanthids may form a strip growing above the soft and hard coral bands. Turbinaria spp. and Goniopora spp. form distinct communities in Hervey Bay[17]. May or may not include intermittent/seasonal macroalgae, which tends to expand its extent in years following flood events[6][7].

Comments

Consolidation is undifferentiated and not diagnostic (i.e. may be either Consolidated, Unconsolidated, Intermediate or Unknown). Other relevant attributes include Energy magnitude (wave) as branching corals frequently grow where there is slight wave action – at levels imperceptible by the very coarse wave Energy attribute dataset. Water clarity is a relevant water column attribute.

Management issues affecting intertidal corals are numerous. In the Central Queensland area, and throughout the Great Barrier Reef lagoon, attributes of Freshwater source and volume are relevant to intertidal corals. Catchment land use and water quality both in the larger area (e.g. a river valley) and immediate proximity (e.g. urban stormwater issues) need to be appropriately managed to minimise sediment, nutrient and freshwater impacts on the reefs. Intertidal corals recovering from flood impacts or bleaching events also require special management such as fishing closures etc. Physically the corals can also disturbed by anchors (breakage) and fishing lines, nets etc (which encourage the growth of bacteria).

Additional Information

Protecting the Great Barrier Reef - Queensland Government

Coral - Department of the Environment, Tourism, Science and Innovation

Coral reefs - Queensland Museum

The Reef - Great Barrier Reef Marine Park Authority

Corals of the World

References

1. ^ Alquezar, R, Scannell, J & Boyd, W (2011), Coastal fringing reefs of the Burnett Mary Region 2011. A report to the Burnett-Mary Regional Group., Centre for Environmental Management, Central Queensland University, Gladstone, Queensland.
2. ^ Anthony, KRN & Connolly, SR (2004), 'Environmental limits to growth: Physiological niche boundaries of corals along turbidity-light gradients', Oecologia, vol. 141, no. 3, pp. 373-384.
3. ^ Ayling, AM, Ayling, AL & Berkelmans, R (1998), Shoalwater Bay fringing reef resource assessment, Great Barrier Reef Marine Park Authority.
4. ^ Beger, M, Sommer, B, Harrison, PL, Smith, SDA & Pandolfi, JM (2014), 'Conserving potential coral reef refuges at high latitudes', Diversity and Distributions, vol. 20, no. 3, pp. 245-257, Wiley Online Library.
5. ^ Browne, NK, Smithers, SG & Perry, CT (March 2013), 'Spatial and temporal variations in turbidity on two inshore turbid reefs on the Great Barrier Reef, Australia', Coral Reefs. [online], vol. 32, no. 1, pp. 195-210. Available at: http://link.springer.com/10.1007/s00338-012-0965-1 [Accessed 15 March 2019].
6. ^ a b Butler, IR, Sommer, B, Zann, M, Zhao, J & Pandolfi, JM (2013), 'The impacts of flooding on the high-latitude, terrigenoclastic influenced coral reefs of Hervey Bay, Queensland, Australia', Coral Reefs, vol. 32, no. 4, pp. 1149-1163, Springer.
7. ^ a b c Butler, IR (2015), Flood response and palaeoecology of the high-latitude, terrigenoclastic influenced coral reefs of Hervey Bay, Queensland, Australia. PhD thesis, School of Biological Sciences The University of Queensland.
8. ^ a b Devantier, LD (2010), Reef-building corals of Hervey Bay, South-East Queensland. [online] Available at: https://www.researchgate.net/publication/285100297_DeVantier_2010_Reef-building_Corals_of_Hervey_Bay_South-east_Queensland.
9. ^ Fabricius, K (2010), 'Octocorallia', in Encyclopedia of Modern Coral Reefs, pp. Chapter-35.
10. ^ Fellegara, I & Harrison, PL (2008), 'Status of the subtropical scleractinian coral communities in the turbid environment of Moreton Bay, southeast Queensland', Proceedings of the Thirteenth International Marine Biological Workshop: The Marine Fauna and Flora of Moreton Bay, Queensland, pp. 277-291.
11. ^ Folk, RL (1974), 'Petrography of sedimentary rocks', Univ.Texas, Hemphill, Austin, Tex, vol. 182.
12. ^ Jones, AM & Berkelmans, R (2014), 'Flood impacts in Keppel Bay, Southern Great Barrier Reef in the aftermath of cyclonic rainfall', PLoS ONE. [online], vol. 9, no. 1. Available at: Scopus.
13. ^ Lybolt, M, Neil, D, Zhao, J, Feng, Y, Yu, KF & Pandolfi, J (2010), 'Instability in a marginal coral reef: the shift from natural variability to a human-dominated seascape', Frontiers in Ecology and the Environment, vol. 9, no. 3, pp. 154-160, Eco Soc America.
14. ^ Mumby, PJ (2006), 'Fishing, Trophic Cascades, and the Process of Grazing on Coral Reefs', Science. [online], vol. 311, no. 5757, pp. 98-101. Available at: http://www.sciencemag.org/cgi/doi/10.1126/science.1121129 [Accessed 3 June 2019].
15. ^ 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.
16. ^ a b c d 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.
17. ^ a b c Zann, M (2012), The use of remote sensing and field validation for mapping coral communities of Hervey Bay and the Great Sandy Strait and implications for coastal planning policy, The University of Queensland.

Last updated: 12 July 2019