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Global regime shift dynamics of catastrophic sea urchin overgrazing

Citation

Ling, SD and Scheibling, RE and Rassweiler, A and Johnson, CR and Shears, N and Connell, SD and Salomon, AK and Norderhaug, KM and Perez-Matus, A and Hernandez, JC and Clemente, S and Blamey, LK and Hereu, B and Ballesteros, E and Sala, E and Garrabou, J and Cebrian, E and Zabala, M and Fujita, D and Johnson, LE, Global regime shift dynamics of catastrophic sea urchin overgrazing, Royal Society of London. Philosophical Transactions. Biological Sciences, 370, (1659) Article 20130269. ISSN 0962-8436 (2015) [Refereed Article]

Copyright Statement

Copyright 2014 The Authors

DOI: doi:10.1098/rstb.2013.0269

Abstract

A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.

Item Details

Item Type:Refereed Article
Keywords:regime shift, marine ecology, overgrazing, temperate reefs, kelp beds, sea urchins
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:Environment
Objective Group:Flora, Fauna and Biodiversity
Objective Field:Marine Flora, Fauna and Biodiversity
Author:Ling, SD (Dr Scott Ling)
Author:Johnson, CR (Professor Craig Johnson)
ID Code:97071
Year Published:2015
Web of Science® Times Cited:54
Deposited By:IMAS Research and Education Centre
Deposited On:2014-12-02
Last Modified:2016-09-04
Downloads:0

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