Oecologia

, Volume 169, Issue 1, pp 187–198

Effects of herbivory, nutrients, and reef protection on algal proliferation and coral growth on a tropical reef

Authors

  • Douglas B. Rasher
    • School of BiologyGeorgia Institute of Technology
  • Sebastian Engel
    • School of BiologyGeorgia Institute of Technology
  • Victor Bonito
    • Reef Explorer Fiji
  • Gareth J. Fraser
    • Department of Animal and Plant SciencesUniversity of Sheffield
  • Joseph P. Montoya
    • School of BiologyGeorgia Institute of Technology
    • School of BiologyGeorgia Institute of Technology
Community ecology - Original Paper

DOI: 10.1007/s00442-011-2174-y

Cite this article as:
Rasher, D.B., Engel, S., Bonito, V. et al. Oecologia (2012) 169: 187. doi:10.1007/s00442-011-2174-y

Abstract

Maintaining coral reef resilience against increasing anthropogenic disturbance is critical for effective reef management. Resilience is partially determined by how processes, such as herbivory and nutrient supply, affect coral recovery versus macroalgal proliferation following disturbances. However, the relative effects of herbivory versus nutrient enrichment on algal proliferation remain debated. Here, we manipulated herbivory and nutrients on a coral-dominated reef protected from fishing, and on an adjacent macroalgal-dominated reef subject to fishing and riverine discharge, over 152 days. On both reefs, herbivore exclusion increased total and upright macroalgal cover by 9–46 times, upright macroalgal biomass by 23–84 times, and cyanobacteria cover by 0–27 times, but decreased cover of encrusting coralline algae by 46–100% and short turf algae by 14–39%. In contrast, nutrient enrichment had no effect on algal proliferation, but suppressed cover of total macroalgae (by 33–42%) and cyanobacteria (by 71% on the protected reef) when herbivores were excluded. Herbivore exclusion, but not nutrient enrichment, also increased sediment accumulation, suggesting a strong link between herbivory, macroalgal growth, and sediment retention. Growth rates of the corals Porites cylindrica and Acropora millepora were 30–35% greater on the protected versus fished reef, but nutrient and herbivore manipulations within a site did not affect coral growth. Cumulatively, these data suggest that herbivory rather than eutrophication plays the dominant role in mediating macroalgal proliferation, that macroalgae trap sediments that may further suppress herbivory and enhance macroalgal dominance, and that corals are relatively resistant to damage from some macroalgae but are significantly impacted by ambient reef condition.

Keywords

Plant-herbivoryEutrophicationFijiMPAOverfishing

Abbreviations

MPA

Marine protected area

Non-MPA

Non-marine protected area

CCA

Crustose coralline algae

RDM

Relative dominance model

Copyright information

© Springer-Verlag 2011