Halimeda bioherms on the Great Barrier Reef
February 03, 2020

The calcareous green alga Halimeda is a major contributor to inter-reef carbonate sediments and is found along the northern Great Barrier Reef shelf as extensive build-ups of sediment, called bioherms.

halimeda meadow sHalimeda algae meadow (credit Emma Kennedy)These Halimeda bioherms represent important inter-reef habitats and potential carbon sinks, and covering an area at least equal to that of the modern coral reefs also found on the northern GBR shelf.

This project utilised new Laser Airborne Depth Sounder (LADS) bathymetry data to reveal a completely different picture of their spatial extent and surface morphology compared to earlier studies of these bioherms.

The new LADS data show the Halimeda bioherms are far more complex than previously thought, which challenge existing ideas describing their origin, development and significance.

halimeda 3d s3D view of inter-reefal biohermsThe Halimeda bioherms project aims to:

  1. Define the spatial distribution and morphological variation of the Halimeda bioherms,
  2. Explore the relationship of the bioherms to the undersea landscape (channels, passages and submarine canyons) and key oceanographic processes,
  3. Develop new 3D models explaining their origin and development, generate Holocene paleo-climate data, including novel archives of upwelling, paleo-flooding and water quality,
  4. Quantify their total volume/area as a regional geological carbon sink within the context of the global carbon budget, and
  5. Assess the importance of the bioherms as modern, inter-reef benthic habitats.

This research will increase our fundamental understanding of the processes that control bioherm development, and have direct implications for environmental managers tasked with predicting how these poorly studied inter-reef environments might respond to future climate change.



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