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Ocean acidification and warming scenarios increase microbioerosion of coral skeletons

Authors

  • Catalina Reyes-Nivia,

    Corresponding author
    1. School of Biological Sciences and Global Change Institute, University of Queensland, St. Lucia, Queensland, Australia
    • Australian Research Council Centre of Excellence for Coral Reef Studies, St. Lucia, Queensland, Australia
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  • Guillermo Diaz-Pulido,

    1. Griffith School of Environment and Australian Rivers Institute – Coast & Estuaries, Griffith University, Nathan, Queensland, Australia
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  • David Kline,

    1. School of Biological Sciences and Global Change Institute, University of Queensland, St. Lucia, Queensland, Australia
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  • Ove-Hoegh Guldberg,

    1. Australian Research Council Centre of Excellence for Coral Reef Studies, St. Lucia, Queensland, Australia
    2. School of Biological Sciences and Global Change Institute, University of Queensland, St. Lucia, Queensland, Australia
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  • Sophie Dove

    1. Australian Research Council Centre of Excellence for Coral Reef Studies, St. Lucia, Queensland, Australia
    2. School of Biological Sciences and Global Change Institute, University of Queensland, St. Lucia, Queensland, Australia
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Correspondence: Catalina Reyes-Nivia, School of Biological Sciences and Global Change Institute, University of Queensland, St. Lucia, Queensland 4072, Australia, tel. +61 7 3365 3548, fax +61 7 3365 2665, e-mail: catalina.reyes@uq.edu.au

Abstract

Biological mediation of carbonate dissolution represents a fundamental component of the destructive forces acting on coral reef ecosystems. Whereas ocean acidification can increase dissolution of carbonate substrates, the combined impact of ocean acidification and warming on the microbioerosion of coral skeletons remains unknown. Here, we exposed skeletons of the reef-building corals, Porites cylindrica and Isopora cuneata, to present-day (Control: 400 μatm – 24 °C) and future pCO2–temperature scenarios projected for the end of the century (Medium: +230 μatm – +2 °C; High: +610 μatm – +4 °C). Skeletons were also subjected to permanent darkness with initial sodium hypochlorite incubation, and natural light without sodium hypochlorite incubation to isolate the environmental effect of acidic seawater (i.e., Ωaragonite <1) from the biological effect of photosynthetic microborers. Our results indicated that skeletal dissolution is predominantly driven by photosynthetic microborers, as samples held in the dark did not decalcify. In contrast, dissolution of skeletons exposed to light increased under elevated pCO2–temperature scenarios, with P. cylindrica experiencing higher dissolution rates per month (89%) than I. cuneata (46%) in the high treatment relative to control. The effects of future pCO2–temperature scenarios on the structure of endolithic communities were only identified in P. cylindrica and were mostly associated with a higher abundance of the green algae Ostreobium spp. Enhanced skeletal dissolution was also associated with increased endolithic biomass and respiration under elevated pCO2–temperature scenarios. Our results suggest that future projections of ocean acidification and warming will lead to increased rates of microbioerosion. However, the magnitude of bioerosion responses may depend on the structural properties of coral skeletons, with a range of implications for reef carbonate losses under warmer and more acidic oceans.

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