Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Reef to island sediment connections within an inshore turbid coral reef island system of the eastern Indian Ocean (#135)

Josh L Bonesso 1 2 3 4 , Nicola K Browne 5 , Matilda Murley 3 6 , Shannon Dee 5 , Michael VW Cuttler 3 7 , Victorien Paumard 1 3 8 , Dylan Benson 5 , Michael O'Leary 1 3
  1. School of Earth Sciences, University of Western Australia, Perth, Western Australia, Australia
  2. ARC Centre of Excellence for Coral Reef Studies , University of Western Australia, Perth, Western Australia, Australia
  3. UWA Oceans Institute, University of Western Australia, Perth, Western Australia, Australia
  4. Western Australian Marine Science Institution , Perth, Western Australia, Australia
  5. School of Life and Molecular Sciences, Curtin University, Perth, Western Australia, Australia
  6. School of Biological Sciences , University of Western Australia, Perth, Western Australia, Australia
  7. Oceans Graduate School, University of Western Australia, Perth, Western Australia, Australia
  8. Centre for Energy Geoscience, University of Western Australia, Perth, Western Australia, Australia

Research into climate impacts on coral reef sediment production and island building have tended to focus on clear-water (oligotrophic) reef-island ecosystems. However, many reef-islands are situated within nearshore environments and characterised by or currently experiencing a reduction in water quality. It is unknown how reef-island sedimentary systems have adapted to or may respond to future reductions in water quality (i.e., increase in turbidity). Thus, improved knowledge of contemporary sediment dynamics within turbid water settings will aid in our understanding of island resilience in the face of future environmental changes. We investigated sediment dynamics of a naturally turbid reef-island system along the nearshore Pilbara coast. Uniquely, molluscan-derived sediments account for (34%) along with coral (27%) of island composition, and this is despite extremely low abundance of living mollusc within the fringing reef flats (n = 94 total individuals). It is unclear as to why there is significantly low abundance of living molluscs while the islands themselves are dominated by molluscan-derived sediments. Given these nearshore islands are comprised of more than one primary sediment constituent, it may suggest that loss of any one source of reef-derived sediment may be compensated by other sediment sources improving the resilience of these turbid-type reef-island systems.