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Stereo-imaging AUV detects trends in sea urchin abundance on deep overgrazed reefs

Citation

Ling, SD and Mahon, I and Marzloff, MP and Pizarro, O and Johnson, CR and Williams, SB, Stereo-imaging AUV detects trends in sea urchin abundance on deep overgrazed reefs, Limnology and Oceanography: Methods, 14, (5) pp. 293-304. ISSN 1541-5856 (2016) [Refereed Article]

Copyright Statement

Copyright 2016 Association for the Sciences of Limnology and Oceanography

DOI: doi:10.1002/lom3.10089

Abstract

Remote underwater vehicles are cutting-edge tools for mapping benthic habitats, yet their reliability for detecting patterns in abundance of benthic species remains largely unexplored. Here, we use a stereo-imaging AUV to investigate changes in abundance of the overgrazing sea urchin, Centrostephanus rodgersii, which has undergone climate driven range-extension to Tasmania. As part of ongoing bi-yearly monitoring of urchin impacts (June 20092013), the benthic stereo-imaging AUV (Sirius) surveyed fixed geo-referenced 25 25 m plots (625 m2) on deep "urchin barrens" (2530 m depth) and shallow barren/kelp transition zones (816 m) at two sites at St. Helens, northeast Tasmania (−41.25; 148.34). Coincident with initial AUV deployments, urchin abundance was also estimated in the same reef plots using conventional SCUBA diver belt-transects; with comparison of AUV and diver sampling showing AUV-derived estimates to be ∼ 40% lower; while additional AUV sampling at night (high risk for divers in deep water) detected abundances only ∼16% lower than that measured by daytime divers, demonstrating strong nocturnal emergence of C. rodgersii. Importantly, patterns in C. rodgersii abundance across reefs and depths were similar between methods; and long-term population trends were concordant between diver and AUV methods. At finer-scales, AUV detections were compromised where remnant kelp canopies obscured urchins, indicating divers to be superior for detecting early-warning of population increases within intact kelp beds. Comparison of C. rodgersii with two other macro-invertebrates (sea cucumber Australostichopus mollis and sea urchin Heliocidaris erythrogramma) revealed that while stereo-imaging AUVs can detect space/time variability in macro-invertebrate abundance, detectability is highly dependent on local ecologies and species-specific behaviours.

Item Details

Item Type:Refereed Article
Keywords:Autonomous Underwater Vehicle, sea urchin, marine invertebrates, benthic community, seafloor, monitoring ecological changes
Research Division:Environmental Sciences
Research Group:Environmental Science and Management
Research Field:Environmental Monitoring
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Coastal and Estuarine Environments
Author:Ling, SD (Dr Scott Ling)
Author:Marzloff, MP (Dr Martin Marzloff)
Author:Johnson, CR (Professor Craig Johnson)
ID Code:107664
Year Published:2016
Web of Science® Times Cited:3
Deposited By:Centre for Ecology and Biodiversity
Deposited On:2016-03-21
Last Modified:2017-11-08
Downloads:0

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