Suppression of herbivory by macroalgal density: a critical feedback on coral reefs?
Coral reefs globally are in decline, with some reefs undergoing phase shifts from coral-dominance to degraded states dominated by large fleshy macroalgae. These shifts have been underpinned by the overharvesting of herbivorous fishes and represent a fundamental change in the physical structure of these reefs. Although the physical structure provided by corals is regarded as a key feature that facilitates herbivore activity, the influence of the physical structure of macroalgal stands is largely unknown. Using transplanted Sargassum, the largest coral reef macroalga, we created habitat patches of predetermined macroalgal density (0.25-6.23 kg m(-2)). Remote video cameras revealed both grazing and browsing fishes avoided high density patches, preferring relatively open areas with low macroalgal cover. This behaviour may provide a positive feedback leading to the growth and persistence of macroalgal stands; increasing the stability of phase shifts to macroalgae.
Australian Research Council Centre of Excellence for Coral Reef Studies and School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia. andrew.hoey@my.jcu.edu.au
Andrew S
AS
Hoey
David R
DR
Bellwood
D000818:Animals; D037421:Anthozoa / Q000502:physiology; D057894:Coral Reefs; D005247:Feeding Behavior; D005399:Fishes / Q000502:physiology*; D010140:Pacific Ocean; D011156:Population Density; D011793:Queensland; D044647:Sargassum / Q000502:physiology*