Wave exposure shapes reef community composition and recovery trajectories at a remote coral atoll

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  • Ines D. Lange
    University of Exeter
  • Cassandra E. Benkwitt
    Lancaster University
  • Jamie M. McDevitt-Irwin
    Stanford University
  • Kristina L. Tietjen
    University of Victoria
  • Brett Taylor
    Australian Institute of Marine Science
  • Mark Chinkin
    Australian Institute of Marine Science
  • Rachel L. Gunn
    Lancaster University
  • Melissa Palmisciano
    Stanford University
  • Margaux Steyaert
    University of Oxford
  • Bry Wilson
    University of Oxford
  • Holly K. East
    Northumbria University
  • John Turner
  • Nicholas A.J. Graham
    Lancaster University
  • Chris T. Perry
    University of Exeter
In a time of unprecedented ecological change, understanding natural biophysical relationships between reef resilience and physical drivers is of increasing importance. This study evaluates how wave forcing structures coral reef benthic community composition and recovery trajectories after the major 2015/2016 bleaching event in the remote Chagos Archipelago, Indian Ocean. Benthic cover and substrate rugosity were quantified from digital imagery at 23 fore reef sites around a small coral atoll (Salomon) in 2020 and compared to data from a similar survey in 2006 and opportunistic surveys in intermediate years. Cluster analysis and principal component analysis show strong separation of community composition between exposed (modelled wave exposure >1000 J m-3) and sheltered sites (<1000 J m-3) in 2020. Differences are driven by relatively high cover of Porites sp., other massive corals, encrusting corals, soft corals, rubble and dead table corals at sheltered sites versus high cover of pavement and sponges at exposed sites. Total coral cover and rugosity were also higher at sheltered sites. Adding data from previous years shows benthic community shifts from distinct exposure-driven assemblages and high live coral cover in 2006 towards dominance of bare pavement, dead Acropora tables and rubble after the 2015/2016 bleaching event. The subsequent, and still ongoing, recovery trajectories at sheltered and exposed sites are surprisingly parallel and lead communities towards their respective pre-bleaching communities. These results demonstrate that in the absence of human stressors, community patterns on fore reefs are strongly controlled by wave exposure, even during and after widespread coral loss from bleaching events.

Keywords

  • community composition; biophysical coupling; wave exposure; wave forcing; exposed; sheltered; recovery trajectory; remote coral reef
Original languageEnglish
Pages (from-to)1819-1829
Number of pages11
JournalCoral Reefs
Volume40
Issue number6
Early online date27 Sept 2021
DOIs
Publication statusPublished - Dec 2021

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