Mangroves

Mangrove community at Booral.

Photo credit: © Queensland Parks and Wildlife Service

The extensive river and creek estuaries within the Great Sandy Marine Park, combined with the sheltered environment of the Great Sandy Strait, provide large areas of ideal habitat for mangroves. Mangroves ‘kick start’ many coastal food chains. Some nutrients are used on the spot, while others are exported with the tides to neighbouring seagrass beds and beyond. At some time in their lives, more than 70% of the commercial and recreational fisheries species depend on mangroves. For example, barramundi spawn in mangrove creeks protected from predators.

Mangrove forests act as stabilisers, which help to reduce excessive sediment flow. They are of particular importance as they form a protective barrier trapping sediments and stabilising shore and river edges, decreasing the threat of erosive action by currents and stream flow.

Mangrove forests are coastal ecosystems that act as ‘net carbon sinks’ - capturing and storing carbon from the atmosphere and ocean, particularly in their sediments, at a rate of 30-50 times faster than terrestrial forests (per unit area)¹. Older stands of mangroves (17-35 years old) hold double the total carbon stocks and have double the sequestration of younger mangroves². Human-induced damage or loss of mangroves from, for example, the impacts of climate change or coastal development, threatens the capacity of mangroves and their associated sediments to store carbon. Any disturbance to mangrove forests and their sediments results in the release of carbon and other greenhouse gases (including methane), and these emissions contribute to climate change³. Therefore, it is important to preserve mangrove ecosystems, particularly stands of older mangroves, to curb greenhouse gas emissions and enable long-term storage of carbon in the sediments of these coastal ecosystems.

There are 10 mangrove species found in the Great Sandy Marine Park which include:

• Grey mangrove (Avicennia marina)
• River mangrove (Aegiceras corniculatum)
• Club mangrove (Aegialitis annulata)
• Large leaf orange mangrove (Bruguiera gymnorhiza)
• Smooth fruit orange mangrove (Ceriops australis)
• Milky mangrove (Excoecaria agallocha)
• White-flowered black mangrove (Lumnitzera racemose)
• Myrtle mangrove (Osbornia octodonta)
• Long style stilt mangrove (Rhizophora stylosa)
• Cannonball mangrove (Xylocarpus granatum)

Some of the mangrove habitats in the marine park include:

• Mary River – extensive mangrove forests line the mouth of the river and its banks
• Susan River – includes stands of cannonball mangroves which are at the southern limit of their distribution and Grey and River mangrove stands which are a recognised habitat for the vulnerable Illidge’s ant blue butterfly
• Islands – there are numerous mangrove dominated islands throughout the Great Sandy Strait
• Creeks – most creek lines throughout the marine park are lined with mangroves to their tidal extent⁴.

Unusual tenants of the mangroves

The water mouse (Xeromys myoides), a protected species, builds large mud nests in mangrove forests and feeds on small crabs and molluscs. Nest structures have been observed at a number of locations within the Great Sandy Strait and Tin Can Inlet. In hollow branches of grey mangroves, the threatened Illidge’s ant-blue butterflies (Acrodipsas illidgei) trick ‘crematogaster’ ants into feeding their own young to the butterfly’s caterpillar.

• Read more about mangroves.

References

¹ Costa, M.D.P.C., Lovelock, C., Waltham, N. and Macreadie, P.I., 2020. Blue Carbon Opportunities in Queensland: how much and where?. A report provided to the Land Restoration Fund, Queensland Government. Deakin University, Melbourne, 34pp.

² Carnell, P.E., Palacios, M.M., Waryszak, P., Trevathan-Tackett, S.M., Masque, P., and Macreadie, P.I. (2022). Blue carbon drawdown by restored mangrove forests improves with age. Journal of Environmental Management, 306, 114301. https://doi.org/10.1016/j.jenvman.2021.114301

³ Ollivier, Q.R., Maher, D.T., Pitfield, C. and Macreadie, P.I., 2022. Net Drawdown of Greenhouse Gases (CO2, CH4 and N2O) by a Temperate Australian Seagrass Meadow. Estuaries and Coasts, https://doi.org/10.1007/s12237-022-01068-8.

⁴ Mackenzie, J. and Duke, N.C., 2011. State of the Mangroves 2008: Condition assessment of the tidal wetlands of the Burnett Mary Region, School of Biological Sciences, University of Queensland, Brisbane

⁵ Kaluza, J., 2018. The Great Sandy Strait Water Mouse Survey and Monitoring Project 2014-2018. BMRG Keep the Strait Great programme in conjunction with The University of Queensland.