Reef habitats – coral and rocky

Moreton Bay Marine Park includes a variety of reef habitats, primarily in the form of inshore fringing reefs around islands within Moreton Bay and offshore rocky reefs. There are also rocky areas of shoreline and rocky headlands along parts of the coast. The Park’s reef habitats support a wide range of marine life and play an important role in recreational, commercial, research and educational activities. A number of artificial reefs in Moreton Bay Marine Park also play an important ecological role – read more about the marine park’s artificial reefs.

Coral

Subtropical Moreton Bay Marine Park is home to over 120 species of hard coral and around 18 soft coral species. The marine park sits at the meeting point of the tropical north and temperate south. This mixing zone gives the marine park unique combinations of temperate and tropical coral species. Coral typically occurs on rocky or hard substrates at depths of less than 15 metres and is often interspersed with adjacent seagrass beds and sandy seafloor habitats.

The marine park’s coral communities change with distance from the mainland. The spread of coral and occurrence of species is evidence of a water quality gradient - with poor water quality close inshore and improving further out into Moreton Bay and in offshore areas. ¹ Hardy coral species occur in inshore communities where the water is warmer and more turbid or murky. There are approximately 40 species of coral within the Bay, with the 'massive coral' (Favia speciosa) dominating.

In the clearer, cooler waters offshore, the fragile 'branching coral' (Acropora) is more common and the diversity of coral is higher; for example, at offshore Flinders Reef, 125 species of hard corals have been recorded.

Many species live in symbiotic relationships with corals, including algae, crustaceans, molluscs, worms, and fish. Zooplankton and other microscopic organisms thrive in the water and reef structures. ² Coral communities serve as critical nursery areas for fish and crustaceans, supporting the broader marine ecosystem.

The marine park's coral reef community peaked about 6,000 years ago when the climate and sea levels were optimal for their growth. At this time, the reefs around Mud Island and along the mainland coast at Wellington and Cleveland Points were actively growing and thriving. The main coral species were the branching Acropora corals, which are now primarily found at Myora and Flinders Reefs.³

In the early 1930s, dredging of coral as a source of calcium carbonate to produce cement for Queensland’s construction industry, began in Moreton Bay. Over the following six decades, the reefs around Mud Island, St Helena Island and to a lesser extent Green Island, were dredged for coral, resulting in the entire reef flat at Mud Island being depleted.⁴ Coral dredging in Moreton Bay came to an end in 1997, with the 1997 marine park zoning plan including the reefs in habitat protection and conservation park zones, contributing to their future and current protection.

Rocky reefs

There are a number of offshore rocky reefs that occur on the eastern side of Moreton and North Stradbroke Islands, which characteristically have a sedimentary (e.g. sandstone) or volcanic rock base. These reefs include Henderson Rock, Cherubs Cave, China Wall, Gotham City, Smith Rocks and Flinders Reef (all near Moreton Island), and Flat Rock, Boat Rock, Shag Rock and Middle Reef near North Stradbroke Island.

Some support significant coral communities, e.g. at Flinders Reef and Flat Rock, where the better light visibility enables coral to grow to deeper areas around the rocks (e.g. down to 40m), relative to their depth range within the Bay.⁵ Other locations such as Cherubs Cave and Henderson Rock are dominated by macroalgae, e.g. kelp, which is being increasingly recognised as having a valuable role as a fish nursery and in supporting juvenile fish. ⁶ Kelp beds are at their northern limit in Queensland waters, with the marine park marking their northern distribution along the east coast. ⁷

The offshore rocky reefs provide habitat for manta ray and shark species, including the threatened grey nurse shark that has been found to seasonally use reef habitat at Cherubs Cave, Henderson Rock and Flat Rock.⁸ These areas are attractive for divers, although their exposure to prevailing swell and oceanic currents means that they are not always accessible.

Impacts

Broad-scale threats to reef habitats include climate change (extreme weather events – floods, cyclones, and an increase in sea temperatures), poor water quality (i.e. terrestrial runoff containing elevated nutrient, sediment and pesticide concentrations ⁹) and coastal development. Reef habitats rely on stable water quality, temperatures, and sunlight. Disruptions to these conditions, particularly rising sea temperatures, can trigger coral bleaching—a stress response where corals expel their symbiotic algae (zooxanthellae), losing their colour and primary energy source.

Over the past decade, marine heatwaves have become more frequent and severe due to human-induced climate change.¹⁰ While the Great Barrier Reef has experienced three mass bleaching events in the past five years, Moreton Bay has not been immune. A 2022 survey observed coral bleaching in the marine park, with inshore reefs such as Peel and St Helena Islands showing moderate to high levels of bleaching (20% and 55%, respectively).¹¹

Offshore reefs like Flinders Reef have shown greater resilience to bleaching due to cooler, clearer waters, but they are not immune to the impacts of prolonged heat stress.

Reef habitats may also be damaged through anchoring or diving. Damaging coral exposes it to attack from other marine organisms and can also upset the structure of the reef. Most divers and snorkellers cause little noticeable damage to corals but fins can cause damage.¹² Anchors also cause physical damage which can lead to localised death of coral colonies.

Protection

Reef habitats are protected under the Moreton Bay Marine Park Zoning Plan through a system of zones, permit requirements, coral collection restrictions and anchoring restrictions.

The zoning plan applies the following restrictions to help protect the marine park's reef habitats:

• Collecting coral is prohibited.
• Commercial tourism involving dive operations require a permit.
• Public moorings have been installed at Flinders Reef and Flat Rock to prevent anchor damage to corals. The marine park also has three designated no anchoring areas located at Flinders Reef, Flat Rock and Myora Reef that assist with preventing anchor damage.

Coral in Moreton Bay Marine Park.

Photo credit: © Chris Roelfsema

References and further reading

1. Hammerman, N. M., Roff, G., Lybolt, T., Eyal, G., and Pandolfi, J. M. (2022). Unraveling Moreton Bay reef history: An urban high-latitude setting for coral development. Frontiers in Ecology and Evolution, 10, 884850.

2. Wolfe, K., Kenyon, T. M., and Mumby, P. J. (2021). The biology and ecology of coral rubble and implications for the future of coral reefs. Coral Reefs, 40, 1769-1806.

3. Wallace, C. C., Fellegara, I., Muir, P. R., and Harrison, P. L. (2009). The scleractinian corals of Moreton Bay, eastern Australia: high latitude, marginal assemblages with increasing species richness. Memoirs of the Queensland Museum, 54(2), 1-118.

4. Butcher, J.G. (2022) The coral dredgers: Queensland Cement and Lime Company and the mining of Moreton Bay, 1931-1997. The Moreton Bay Foundation Ltd: Newstead, Queensland. The Coral Dredgers - The Moreton Bay Foundation The Coral Dredgers - The Moreton Bay Foundation

5. Roelfsema, C., Loder, J., Hay, K., Kleine, D., Grol, M. and Kovacs, E. (2019). Building an understanding of Moreton Bay Marine Park reefs through citizen science. In Tibbetts, I.R., Rothlisberg, P.C., Neil, D.T., Homburg, T.A., Brewer, D.T., and Arthington, A.H. (Editors). Moreton Bay Quandamooka & Catchment: Past, present, and future. The Moreton Bay Foundation. Brisbane, Australia. Available from: https://moretonbayfoundation.org/

6. James, N.C. and Whitfield, A.K. (2023). The role of macroalgae as nursery areas for fish species within coastal seascapes. Cambridge Prisms: Coastal Futures, 1, e3, 1–10 https://doi.org/10.1017/cft.2022.3

7. Marzinelli E.M., Williams S.B., Babcock R.C., Barrett N.S., Johnson C.R., Jordan A., et al. (2015). Large-Scale Geographic Variation in Distribution and Abundance of Australian Deep-Water Kelp Forests. PLoS ONE 10(2): e0118390. doi:10.1371/journal.pone.0118390

8. Dwyer, R.G., Rathbone, M., Foote, D.L., Bennett, M., Butcher, P.A., Otway, N.M., Louden, B.M., Jaine, F.R.A., Franklin, C.E. and Kilpatrick, C. (2023). Marine reserve use by a migratory coastal shark, Carcharias taurus. Biological Conservation, 283. https://doi.org/10.1016/j.biocon.2023.110099.

9. Tuttle, L. J., and Donahue, M. J. (2022). Effects of sediment exposure on corals: a systematic review of experimental studies. Environmental Evidence, 11(1), 1-33.

10. Climate Council (2022) Briefing: In hot water: climate change, marine heatwaves and coral bleaching. https://www.climatecouncil.org.au/resources/hot-water-climate-change-marine-heatwaves-coral-bleaching/

11. Report Card Catchment Summaries 2022, Healthy Land & Water.

12. Rouphael, A. B. and Inglis, G. J. (1997). Impacts of recreational scuba diving at sites with different reef topographies. Biological Conservation, 82, 329-336.