Standard Presentation Australian Marine Sciences Association Annual Meeting 2023

Geomorphological drivers of deep shelf benthic reef communities off the southwest coast of Tasmania   (#127)

Rachel Wong 1 , Jacquomo Monk 1 , Nicholas Perkins 1 , Neville Barrett 1
  1. Institute for Marine & Antarctic Studies, University of Tasmania, Hobart, TASMANIA, Australia

Compared to the shallower waters of the Tasmanian coast, less is known about how offshore benthic reef communities beyond algal depths are structured by natural gradients and anthropogenic stressors. This study presents a comprehensive characterisation of sessile invertebrates and reef habitats from the Tasmanian Shelf, within and encompassing the Tasman Fracture Marine Park (TFMP; 50 – 160 m deep). We identified 324 sessile morphospecies from random sub-sampling of high-resolution seabed imagery of representative reef systems using the IMOS autonomous underwater vehicle facility. Terrain variables derived from previously obtained high-resolution multibeam acoustic mapping of the survey area including depth, rugosity, aspect, slope, and Bathymetric Position Index were used to explore potential relationships with the distribution of morphospecies. Broadly, a cover of turf-like matrix of miniature bryozoans, cnidarians, and sponges dominated the reefs most likely exposed to high wave energy (67%); followed by sponges (21% cover). The distribution of individual morphospecies, taxonomic groups, and their growth forms were related to variations in terrain features and potential interactions with the unique oceanographic processes influencing the TFMP. These findings can help in understanding how TFMP’s mesophotic communities in the exposed areas will be subjected to higher wave energy with climate change.