Poster Presentation 2024 Australian Marine Sciences Association Annual Meeting combined with NZMSS

New approach: Geomorphometric analysis and benthic terrain classification of Halimeda bioherms on the northern Great Barrier Reef (#742)

Zsanett Szilagyi 1 2 , Luke Nothdurft 1 , Jody Webster 2 , Stephanie Duce 3 , Mardi McNeil 1 4 , Robin Beaman 5 , Juan Carlos Braga 6 , Amy Nau 7 , Christopher Berry 7 , Victorien Paumard 8 , Jeffrey Shragge 9 , Helen Bostock 10
  1. Queensland University of Technology, Brisbane, QLD, Australia
  2. The University of Sydney, Sydney, NSW, Australia
  3. James Cook University, Townsville, QLD, Australia
  4. Geoscience Australia, Canberra, ACT, Australia
  5. James Cook University, Cairns, QLD, Australia
  6. University of Granada, Granada, Andalusia, Spain
  7. Commonwealth Scientific and Industrial Research Organisation (CSIRO), Hobart, TAS, Australia
  8. University of Western Australia, Perth, WA, Australia
  9. Colorado School of Mines, Denver, CO, USA
  10. University of Queensland, Brisbane, QLD, Australia

Halimeda accumulations form some of the largest connected biogenic structures in the Great Barrier Reef covering >6000 km2 of the continental shelf, exceeding the area of adjacent coral reefs at equivalent latitudes1. Previous studies showed the shapes and patterns of these accumulations are complex with bathymetric data revealing honeycomb-like surfaces classified into three different morphological sub-types (reticulate, annulate, undulate)1,2.

This study presents new data from the 2022 RV Investigator voyage IN2022_V07 “Halimeda bioherms: Origins, function and fate in the northern Great Barrier Reef (HALO)”, which collected the first sub-metre resolution (50 cm) multibeam bathymetry data of its kind over three inter-reef sites (Ribbon, Cormorant and Tijou Reefs). These high spatial resolution datasets map over 500 linear kilometres, and were analysed with a novel approach, Geomorphon Landforms (ArcGIS Pro), which employs pattern recognition rather than differential geometry to define benthic features. Benthic terrain classification was completed over the bioherms, uncovering six different benthic structures, and quantifying their associated terrain complexity metrics. This detailed bathymetric interrogation is complemented by targeted seafloor images and surface sediment samples that show a complex connected bioherm structure. The increased resolution from our investigation reveals previously unseen complexity and variable seafloor characters within and across morphotypes.

  1. McNeil, M. A., Webster, J. M., Beaman, R. J., and Graham, T. L., 2016, New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia: Coral Reefs, v. 35, no. 4, p. 1343-1355.
  2. McNeil, M., Nothdurft, L. D., Dyriw, N. J., Webster, J. M., and Beaman, R. J., 2021, Morphotype differentiation in the Great Barrier Reef Halimeda bioherm carbonate factory: Internal architecture and surface geomorphometrics: The Depositional Record, v. 7, p. 176– 199.