Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

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Effects of herbivores, wave exposure, and depth on benthic coral communities of the Easter Island Ecoregion

Erin Easton , Carlos Gaymer , Alan Friedlander , James Herlan

Abstract

The Easter Island Ecoregion includes Rapa Nui (Easter Island; RN), with a human population of ~5,600, and uninhabited Salas y Gómez (SyG). While the culture and terrestrial ecology of RN have been well studied, we know little about the marine environment of these islands, particularly the interplay among herbivores, algae, and corals and how coral reef communities differ between islands, by wave-energy exposure, and between depths. To address the potential roles of herbivores, wave-energy exposure, and depth on the sessile benthic communities, we examined herbivorous fish biomass, sea urchin (Diadema savignyi) density, algal, and coral cover to identify patterns and relationships among these groups. We found significant differences between islands. For example, turf and macroalgae were nearly absent from SyG, whereas D. savignyi density and Kyphosus sandwicensis biomass were ~28 and ~3 times greater, respectively, at SyG. Benthic cover of coral and algae and density of D. savigny significantly differed among levels of wave exposure, especially between stations protected from wave exposure and those semi-exposed and/or exposed. Likewise, community structure significantly differed at protected stations. Concordant patterns between herbivores and algae were observed. Therefore, herbivores and wave-energy likely play important roles in structuring these benthic communities, especially for algal groups.

MF17064  Accepted 16 November 2017

© CSIRO 2017