Mesophotic benthic communities associated with a submerged palaeoshoreline in Western Australia

PLOS ONE RESEARCH ARTICLE Mesophotic benthic communities associated with a submerged palaeoshoreline in Western Australia Mary Wakeford ID1*, Marji Puotinen1, William Nicholas2, Jamie Colquhoun1, Brigit I. Vaughan3, Steve Whalan1,4, Iain Parnum ID5, Ben Radford1, Mark Case1, Ronen Galaiduk1, Karen J. Miller1 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Australian Institute of Marine Science, Indian Ocean Marine Research Centre, University of Western Australia, Crawley, Western Australia, Australia, 2 Private Contractor, Queanbeyan, New South Wales, Australia, 3 Department of Biodiversity, Conservation and Attractions, Technology Park, Western Precinct, Kensington, Western Australia, Australia, 4 Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia, 5 Centre for Marine Science and Technology, Curtin University, Bentley, Western Australia, Australia * Abstract OPEN ACCESS Citation: Wakeford M, Puotinen M, Nicholas W, Colquhoun J, Vaughan BI, Whalan S, et al. (2023) Mesophotic benthic communities associated with a submerged palaeoshoreline in Western Australia. PLoS ONE 18(8): e0289805. https://doi.org/ 10.1371/journal.pone.0289805 Editor: Shamim Ahmad, Birbal Sahni Institute of Palaeosciences: Birbal Sahni Institute of Palaeobotany, INDIA Received: March 13, 2023 Accepted: July 27, 2023 Published: August 16, 2023 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0289805 Copyright: © 2023 Wakeford et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper, or accessible from the Australian Institute of Marine Science Data Centre repository: Key ecological features (KEFs) are elements of Australia’s Commonwealth marine environment considered to be important for biodiversity or ecosystem function, yet many KEFs are poorly researched, which can impede effective decision-making about future development and conservation. This study investigates a KEF positioned over the Last Glacial Maximum (LGM) shoreline on the northwest shelf of Australia (known as the ‘Ancient Coastline at ~125m depth contour’; AC125). Seafloor bathymetry, sedimentology and benthic habitats were characterised within five study areas using multibeam sonar, sediment samples and towed video imagery. Direct evidence for the existence of a palaeoshoreline formed during the LGM was not found, however candidate areas to find palaeoshoreline material at or just below the modern seabed were discovered. Approximately 98% of the seabed surveyed was comprised of unconsolidated soft sediment habitat (mud/sand/silt) supporting negligible epibenthic biota. The prevalence of soft sediment suggests that post-glacial sediments have infilled parts of the palaeoshoreline, with cross-shelf, probably tidal currents in the northern section of the study area responsible for some of the sediment mobilisation and southern study areas more influenced by oceanic conditions. Within study areas, total biotic cover ranged from 0.02% to 1.07%. Of the biota encountered, most comprised filter feeder organisms (including gorgonians, sponges, and whip corals) whose distribution was associated with pockets of consolidated hard substrate. Benthic community composition varied with both study area and position in relation to the predicted AC125. In general, consolidated substrate was proportionally higher in water shallower than the AC125 compared to on the AC125 or deeper than the AC125. Spatially continuous maps of predicted benthic habitat classes (pre-determined benthic communities) in each study area were developed to characterise biodiversity. Spatial modelling corroborated depth and large-scale structural complexity of the seafloor as surrogates for predicting likely habitat class. This study provides an important assessment of the AC125 and shows that if a distinct coastline exists in the areas PLOS ONE | https://doi.org/10.1371/journal.pone.0289805 August 16, 2023 1 / 26 PLOS ONE NWSSRP Theme 2 - Project 2a: Characterising the Ancient Coastline Key Ecological Feature (KEF) website (https://apps.aims.gov.au/metadata/view/ 6b325d80-a983-452a-97e6-39bb723245e6). Funding: AIMS’ North West Shoals to Shore Research Program is proudly supported by Santos (www.santos.com) as part of the company’s commitment to better understand Western Australia’s marine environment. The funders had no role in the study design, data collection and analysis, decision to publish or the preparation of the manuscript. Competing interests: Santos is the commercial funder of this research yet they had no role in the study design, data collection and analysis, the decision to publish or the preparation of the manuscript. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Mesophotic benthic communities associated with a submerged palaeoshoreline in Western Australia we surveyed, it is now largely buried and as such does not provide a unique hard substrate habitat. However, much work remains to fully locate and map the ancient coastline within the vast region of the AC125 and additional surveys in shallow waters adjacent to the AC125 may identify whether some sections lie outside the currently defined KEF. Introduction Marine ecosystems cover about 70 percent of the Earth’s surface and include the open ocean, the deep-sea ocean, and coastal marine ecosystems; all of which are ecologically, culturally, and economically valuable [1]. Nearly half of the world’s population live near the coast [2] and activities such as overfishing, coastal development and pollution can threaten the health and sustainability of these areas. The vulnerability and value of marine ecosystems is recognised through management that contributes to the protection of representative areas which are spatially distributed [3]. Management tools include ecosystem-based approaches that incorporate a holistic approach to managing the entire ecosystem by considering all the links among the living and nonliving resources to extend protection across biota and habitats, with an overarching aim to protect ecological, cultural, and economical values [4]. Effective spatial management that endeavours to conserve and protect biodiversity is grounded in knowledge of biogeographic patterns and habitat heterogeneity within ecosystems [4, 5]. Australian Commonwealth waters are among the largest marine jurisdictions in the world and support significant biodiversity found around mainland Australia, (...truncated)