Hot off the press! The rise and fall of the Great Barrier Reef over the past 30,000 years

Fossil coral from the last ice age (credit: IODP/ECORD)

Hi all, well we made it at last.

Please find our new paper just published today in the journal Nature Geoscience

Webster, J. M., Braga, J. C., Humblet, M., Potts, D. C., Iryu, Y., Yokoyama, Y., Fujita, K., Bourillot, R., Esat, T. M., Fallon, S., Thompson, W. G., Thomas, A. L., Kan, H., McGregor, H. V., Hinestrosa, G., Obrochta, S. P., and Lougheed, B. C., 2018. Response of the Great Barrier Reef to sea level and environmental changes over the past 30,000 years. Nature Geoscience. https://doi.org/10.1038/s41561-018-0127-3

Note the paper can also be freely accessed and viewed online at the following link:

https://rdcu.be/Prgb

We present a synthesis of all the available geomorphic, sedimentological, biological and dating information from fossil reef cores recovered from the GBR shelf-edge reefs during Integrated Ocean Discovery Program (IODP) Expedition 325.

Drill rig on the Great Ship Maya (credit: IODP/ECORD)

The study is entirely novel as it is the first of its kind to reconstruct the evolution of the GBR reef over the past 30,000 years in response to major environmental changes (sea level rise, temperature rise and sediment input/poor water quality). We document how the GBR responded to these major environmental variations, including corresponding changes to reef morphologies, communities and growth rates. We also confirm the existence and location of reef refugia during the LGM sea level and establish the critical environmental conditions at which the reef died and re-established on centennial–millennial timescales over the past 30 kyr.

Some highlights of the paper include:

  • The GBR had a complex and dynamic history of reef growth and demise over the past 30 kyr, characterized by five distinct reef sequences.
  • Each reef sequence consists of coherent, coeval shallow and deep reef habitats that can be traced in space and time.
  • We established the nature and timing of the reef initiation and demise events, documented the corresponding changes in coral–algal assemblages, reef growth rates and the palaeoenvironmental conditions at each stage of the GBR’s development.
  • The GBR shows a remarkable capacity to laterally migrate as it tracked falling and rising sea levels.
  • We identified two different types of reef death/demise events, one caused by subaerial exposure during falling sea level and the another caused by drowning as sea level rose beyond the capacity of the reef to keep up.
  • As an ecosystem the GBR has been more resilient to past sea-level and temperature fluctuations than previously thought, but it has been highly sensitive to increased sediment input over centennial–millennial timescales.

Drill string entering the ship’s moon pool to recovered fossil reef deposits from beneath the sea bed (credit: IODP/ECORD)

We did the original drilling site survey in 2007 on the RV Southern Surveyor so it has been quite a journey to get here. I am proud of this work and it has been truly a team effort. I would really like to thank all my co-authors across Australia and around the world for their wonderful contributions to not only this paper but to the ongoing success of the IODP Expedition 325.

Cheers

Jody

#MarineScienceSydneyUni

Cartoon showing the evolution of the Great Barrier Reef between about 30-10 ka (credit: James Keane/Nature Geoscience; https://doi.org/10.1038/s41561-018-0127-3).

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