University of Tasmania
Browse

File(s) under permanent embargo

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

journal contribution
posted on 2023-05-21, 05:51 authored by Loffler, Z, Alexia Graba-LandryAlexia Graba-Landry, Kidgell, JT, McClure, EC, Pratchett, MS, Hoey, AS

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.

History

Publication title

Coral Reefs

Volume

37

Pagination

1075-1084

ISSN

0722-4028

Department/School

Institute for Marine and Antarctic Studies

Publisher

Springer-Verlag

Place of publication

175 Fifth Ave, New York, USA, Ny, 10010

Rights statement

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

Repository Status

  • Restricted

Socio-economic Objectives

Ecosystem adaptation to climate change

Usage metrics

    University Of Tasmania

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC