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Strong Depth-Related Zonation of Megabenthos on a Rocky Continental Margin (∼700–4000 m) off Southern Tasmania, Australia

Thresher, Ronald and Althaus, Franziska and Adkins, Jess and Gowlett-Holmes, Karen and Alderslade, Phil and Dowdney, Jo and Cho, Walter and Gagnon, Alex and Staples, David and McEnnulty, Felicity and Williams, Alan (2014) Strong Depth-Related Zonation of Megabenthos on a Rocky Continental Margin (∼700–4000 m) off Southern Tasmania, Australia. PLoS ONE, 9 (1). Art. No. e85872. ISSN 1932-6203. PMCID PMC3899097.

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Assemblages of megabenthos are structured in seven depth-related zones between ~700 and 4000 m on the rocky and topographically complex continental margin south of Tasmania, southeastern Australia. These patterns emerge from analysis of imagery and specimen collections taken from a suite of surveys using photographic and in situ sampling by epibenthic sleds, towed video cameras, an autonomous underwater vehicle and a remotely operated vehicle (ROV). Seamount peaks in shallow zones had relatively low biomass and low diversity assemblages, which may be in part natural and in part due to effects of bottom trawl fishing. Species richness was highest at intermediate depths (1000–1300 m) as a result of an extensive coral reef community based on the bioherm-forming scleractinian Solenosmilia variabilis. However, megabenthos abundance peaked in a deeper, low diversity assemblage at 2000–2500 m. The S. variabilis reef and the deep biomass zone were separated by an extensive dead, sub-fossil S. variabilis reef and a relatively low biomass stratum on volcanic rock roughly coincident with the oxygen minimum layer. Below 2400 m, megabenthos was increasingly sparse, though punctuated by occasional small pockets of relatively high diversity and biomass. Nonetheless, megabenthic organisms were observed in the vast majority of photographs on all seabed habitats and to the maximum depths observed - a sandy plain below 3950 m. Taxonomic studies in progress suggest that the observed depth zonation is based in part on changing species mixes with depth, but also an underlying commonality to much of the seamount and rocky substrate biota across all depths. Although the mechanisms supporting the extraordinarily high biomass in 2000–2500 m depths remains obscure, plausible explanations include equatorwards lateral transport of polar production and/or a response to depth-stratified oxygen availability.

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URLURL TypeDescription CentralArticle
Adkins, Jess0000-0002-3174-5190
Additional Information:© 2014 Thresher 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. Received: January 20, 2013; Accepted: December 9, 2013; Published: January 22, 2014. We thank E. Anagnostou, A. Beck, R. Gurney, S. John, A. Kennedy, H. Kippo, N. Meckler, D. Mills, A. Subhas and N. Thiagarajan, and the crews of the AUV ABE, the ROV Jason and RV Thomas T. Thompson and RV Southern Surveyor for their invaluable and professional assistance in the field, S. Cairns, D. Fautin, and K. Moore for taxonomic assistance, E. Druffel for discussions about deep-water carbon sources, P. Brodie for assisting in the photographic analyses and R. Kloser, K. Kemp and an anonymous reviewer for helpful comments on the manuscript. Funding: Components of this work were supported by the National Science Foundation, the Australian Department of Environment, Water, Heritage, and the Arts, the Australian Commonwealth Environmental Research Fund, a grant of ship time by the Australian National Research Facility, and the CSIRO Wealth from Oceans and Climate Adaptation Flagships. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Author Contributions: Conceived and designed the experiments: JA RT. Performed the experiments: JA WC AG KG-H DS RT. Analyzed the data: FA PA JD KG-H FM RT AW. Wrote the paper: FA JA PA RT AW.
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Australian Department of Environment, Water, Heritage, and the ArtsUNSPECIFIED
Australian Commonwealth Environmental Research FundUNSPECIFIED
Australian National Research FacilityUNSPECIFIED
CSIRO Wealth from Oceans and Climate Adaptation FlagshipsUNSPECIFIED
Issue or Number:1
PubMed Central ID:PMC3899097
Record Number:CaltechAUTHORS:20140310-094201992
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Official Citation:Thresher R, Althaus F, Adkins J, Gowlett-Holmes K, Alderslade P, et al. (2014) Strong Depth-Related Zonation of Megabenthos on a Rocky Continental Margin (∼700–4000 m) off Southern Tasmania, Australia. PLoS ONE 9(1): e85872. doi:10.1371/journal.pone.0085872
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44210
Deposited By: Jason Perez
Deposited On:12 Mar 2014 14:40
Last Modified:24 Feb 2020 10:30

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