DOI: 10.5061/dryad.6324j
title: Data from: Competitors as accomplices: seaweed competitors hide corals from predatory starfish

description: Indirect biotic effects arising from multispecies interactions can alter
 the structure and function of ecological communities—often in surprising
 ways that can vary in direction and magnitude. On Pacific coral reefs,
 predation by the crown-of-thorns sea star, Acanthaster planci, is
 associated with broad-scale losses of coral cover and increases of
 macroalgal cover. Macroalgal blooms increase coral–macroalgal competition
 and can generate further coral decline. However, using a combination of
 manipulative field experiments and observations, we demonstrate that
 macroalgae, such as Sargassum polycystum, produce associational refuges
 for corals and dramatically reduce their consumption by Acanthaster. Thus,
 as Acanthaster densities increase, macroalgae can become coral mutualists,
 despite being competitors that significantly suppress coral growth. Field
 feeding experiments revealed that the protective effects of macroalgae
 were strong enough to cause Acanthaster to consume low-preference corals
 instead of high-preference corals surrounded by macroalgae. This
 highlights the context-dependent nature of coral–algal interactions when
 consumers are common. Macroalgal creation of associational refuges from
 Acanthaster predation may have important implications for the structure,
 function and resilience of reef communities subject to an increasing
 number of biotic disturbances.
description: Influence of macroalgal
 contact on coral growthExcel spreadsheet (.xls)
 of data from field-based manipulative experiment measuring monthly changes
 in coral (Montipora hispida) mass from December 2013 to March 2014. Corals
 were exposed to one of five algal treatments: 0, 2, 4, 6, or 8 fronds of
 the brown alga Sargassum polycystum (frond length = 15-20 cm). Numbers in
 column A indicate the parent colony from which a coral originated, and
 numbers in column B indicate the number of Sargassum fronds in contact
 with the coral. The percent change in coral mass was determined using the
 total change in mass (column G) and initial coral mass (column
 C).Clements
 and Hay_Influence of macroalgal contact on coral
 growth.xlsxInfluence of
 coral-macroalgal contact on Acanthaster planci feeding
 behaviourExcel (.xls)
 spreadsheets detailing results of field surveys and manipulative
 experiments investigating the influence of coral-macroalgal contact on
 Acanthaster planci feeding behaviour. Sheet 1 includes data from the field
 survey conducted during July-August 2013 on Votua Reef, Viti Levu, Fiji.
 Column A indicates individual Acanthaster feeding incidents on the coral
 Montopira hispida. These include the coral that was attacked (Primary) and
 5 nearest-neighboring Montipora colonies (Secondary), which are indicated
 in column B. The percent of each colony covered in macroalgae or attacked
 by Acanthaster are included in columns D and E, respectively. Sheet 2
 includes data from feeding choice experiments conducted during July-August
 2012. Individual starfish were given a choice between Montipora surrounded
 by Sargassum polycystum or plastic Sargassum mimics of varying frond
 densities and lengths vs. Montipora that lacked Sargassum or Sargassum
 mimics. Column F indicates the 1st coral attacked (0 = lacked
 Sargassum/mimics, 1 = surrounded by Sargassum/mimics). Sheet 3 includes
 data from feeding choice experiments conducted during June 2013.
 Individual starfish were offered a choice between either Montipora hispida
 or Porites cylindrica that both lacked surrounding Sargassum (0, column
 B), or where the choice was between Montipora surrounded by Sargassum or
 Porites that lacked surrounding Sargassum (1, column
 B).Clements
 and Hay_Influence of coral-macroalgal contact on Acanthaster planci
 feeding behaviour .xlsx