9/03/2023 Please find below our new Science Update article published the science news magazine EOS. Webster, J.M., McNeil, M.A., Bostock, H., Nothdurft, L. and Byrne, M.N., 2023. Making sense of the Great Barrier Reef’s mysterious green donuts. EOS. https://doi.org/10.1029/2023EO230079 This short article summarises some of the highlights from our recent RV Investigator voyage to the GBR to investigate the amazing Halimeda bioherms, as well as the exciting promise of what we hope to achieve with the post voyage scientific work. Many thanks to the entire HALO science team, Marine National Facility (MNF) staff and RV Investigator crew who supported the voyage. 7/11/2022 Important HALO update: Following our recent CSIRO RV Investigator voyage to investigate the Halimeda bioherms in the northern Great Barrier Reef, I wanted to acknowledge the amazing contributions from entire HALO science team – both offshore & shore-based – that contributed to it’s great success. The entire team looks forward now to diving into the post cruise science objectives. To the wider scientific community, if you’re interested in being part of this collaborative project please don’t hesitate to reach out. Jody #MarineScienceSydneyUni HALO Science team members

Name	Institution	Offshore/Shore-based
Jody Webster	USYD	Offshore
Maria Byrne	USYD	Offshore
Matthew Clements	USYD	Offshore
Monique Webb	USYD	Offshore
Luke Nothdurft	QUT	Offshore
Zsanett Szilagyi	QUT	Offshore
Trevor Graham	QUT	Offshore
Robin Beaman	JCU	Shore-based
Stefano Borghi	JCU	Offshore
Tom Bridge	JCU/Qld Museum	Shore-based
Helen Bostock	UQ	Offshore
Kimberley Chua	UQ	Offshore
Molly Husdell	UQ	Offshore
Patrick Moss	UQ	Shore-based
Darren Skene	Quaternary Resources	Offshore
Mardi McNeil	Geosciences Australia	Offshore
Juan Carlos Braga	Universidad de Granada	Offshore
Angel Puga-Bernabeu	Universidad de Granada	Shore-based
Bethany Behrens	University of Tokyo	Offshore
Yuning Zeng	University of Tokyo	Offshore
Yusuke Yokoyama	University of Tokyo	Shore-based
Dirk Erler	Southern Cross University	Shore-based
Willem Renema	Naturalis, Biodiversity Center	Shore-based
Pat Hutchings	Australian National Museum	Shore-based
Matthew Kosnik	Macquarie University	Shore-based
Carra Williams	USYD	Shore-based
Victorien Paumard	UWA	Shore-based
Juliet Sefton	Monash University	Shore-based
Jeffrey Shragge	Colorado School of Mines	Shore-based

Jun 23, 2018  Hi all, it gives me great pleasure to announce that we have been officially awarded an RV Investigator voyage to study the Halimeda (green calcareous algae) build-ups in the Great Barrier Reef (project details below). With colleagues from JCU, QUT, UQ, Queensland Museum and overseas, we have been awarded 33 days of shiptime in 2020 from the Marine National Facility. Important update: Due to COVID-19 the Marine National Facility has now rescheduled this voyage for ~Aug-Sep 2022. This is positive news and voyage planning is well advanced and on track for this new schedule. Project summary: Calcareous green alga Halimeda is a major contributor to coral reef shelf sediments and is found along the entire GBR. Previous studies of extensive Halimeda deposits, or bioherms, show they represent important inter-reef habitats and potential carbon sinks in the GBR Marine Park, covering about 26% of the northern shelf area, at least equal to the modern coral reef system. Pioneering work in 70-80s using widely-spaced, singlebeam and seismic profiles indicate the bioherms are in depths of ~20-40 m and form linear ridges and flat-topped mounds up to 20 m thick. However, new bathymetry data reveals a completely different picture of their surface morphology; characterised by complex reticulate (honeycomb-like) shapes and cyclical internal reflectors continuous over 100s of m. These new findings suggest Halimeda bioherms are more complex than previously thought – challenging existing paradigms describing their origin, development and significance. We will conduct high-resolution multibeam swath mapping and sub-bottom profiling, in conjunction with autonomous and remotely operated underwater vehicles (AUVs, ASV, ROV) seabed imaging, and sediment coring at strategic locations. Key scientific objectives of HALO are 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. Exciting times ahead. Cheers Jody #MarineScienceSydneyUni