Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Rubble in Focus: Establishing a baseline and examining characteristics of unconsolidated reef rubble substrates across the Great Barrier Reef (#130)

Tanya Dodgen 1 , Scott Bryan 1 , Julio Salcedo-Castro 1 , Chris Roelfsema 2
  1. Queensland University of Technology, Brisbane, QLD, Australia
  2. University of Queensland, Brisbane

Reef rubble is a common substrate comprised of unconsolidated carbonate materials of biological origin. Mobile rubble is considered incompatible with hard coral restoration due to its tendency to abrade or bury corals. The sedimentological and ecological properties of rubble have been studied at the scale of individual reefs. However, reef restoration is increasingly investing in regional-scale management to respond to disturbances such as cyclones and heat waves. Our understanding of rubble at these larger scales is virtually non-existent. Benthic habitat maps published in 2021 allow us, for the first time, to examine the spatial distribution and characteristics of rubble across the entire Great Barrier Reef (GBR). Initial results show that over 95% of GBR offshore reefs have less than 20% cover by rubble, including 17% which have no rubble cover. Thus, at present, rubble is unlikely to significantly hinder hard coral recruitment and growth on the GBR. Continuing this investigation will allow us to describe a 2018/19 baseline for GBR rubble cover, against which future changes can be assessed. This baseline could also be used in combination with trends in hard coral cover to identify if ‘rubble of concern’ exists that might be a candidate for restoration interventions.