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Holdfasts of Sargassum swartzii are resistant to herbivory and resilient to damage


Loffler, Z and Graba-Landry, A and Kidgell, JT and McClure, EC and Pratchett, MS and Hoey, AS, Holdfasts of Sargassum swartzii are resistant to herbivory and resilient to damage, Coral Reefs, 37 pp. 1075-1084. ISSN 0722-4028 (2018) [Refereed Article]

Copyright Statement

Copyright Springer-Verlag GmbH Germany, part of Springer Nature 2018

DOI: doi:10.1007/s00338-018-01745-w


The importance of herbivory in both preventing and reversing shifts to macroalgae dominance on coral reefs has been extensively investigated. However, most studies examining the capacity for herbivores to consume fleshy macroalgae (e.g., Sargassum) have investigated removal of the ‘leafy’ biomass without considering the susceptibility of other components of the macroalga, in particular the holdfast, to herbivory. Here, we investigate the susceptibility of Sargassum components (blades, stipes and holdfasts) to herbivory and investigate the capacity for Sargassum to regrow following damage to the holdfast. We placed entire thalli of Sargassum swartzii on the reef crest at Lizard Island, northern Great Barrier Reef, for 24 d, and used photographs and video recordings to quantify rates of removal over this period. The blades of the S. swartzii were rapidly removed (100% in 2 d), whereas the stipes were less susceptible to herbivores, with 72% of experimental thalli having partial stipes remaining after 24 d. Only one holdfast (out of 54) was removed during the experiment, while all of the remaining holdfasts were largely undamaged. When S. swartzii holdfasts were experimentally damaged, we found no detectable effect on thallus height or holdfast size among regrown thalli after 1 y. There was, however, a 50% reduction in survival for S. swartzii individuals when 75% of the holdfast was removed. This study shows that holdfasts of S. swartzii are extremely resistant to herbivory, and that incidental bites on S. swartzii holdfasts are unlikely to affect their growth or survival unless three-quarters of the holdfast is removed. The capacity of Sargassum to regenerate from damaged holdfasts, coupled with the low rate of herbivory on holdfasts, suggests that sustained browsing (preventing regrowth of the stipe and blades) may be more important in reversing macroalgae dominance than physical removal of holdfasts by herbivorous fishes.

Item Details

Item Type:Refereed Article
Keywords:herbivory, Sargassum, holdfasts, regime shift, coral reef, nitrogen
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Adaptation to climate change
Objective Field:Ecosystem adaptation to climate change
UTAS Author:Graba-Landry, A (Dr Alexia Graba-Landry)
ID Code:148889
Year Published:2018
Web of Science® Times Cited:15
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2022-02-17
Last Modified:2022-03-03

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