title: Variable responses of benthic communities to anomalously warm sea temperatures on a high-latitude coral reef.
abstract: High-latitude reefs support unique ecological communities occurring at the biogeographic boundaries between tropical and temperate marine ecosystems. Due to their lower ambient temperatures, they are regarded as potential refugia for tropical species shifting poleward due to rising sea temperatures. However, acute warming events can cause rapid shifts in the composition of high-latitude reef communities, including range contractions of temperate macroalgae and bleaching-induced mortality in corals. While bleaching has been reported on numerous high-latitude reefs, post-bleaching trajectories of benthic communities are poorly described. Consequently, the longer-term effects of thermal anomalies on high-latitude reefs are difficult to predict. Here, we use an autonomous underwater vehicle to conduct repeated surveys of three 625 m(2) plots on a coral-dominated high-latitude reef in the Houtman Abrolhos Islands, Western Australia, over a four-year period spanning a large-magnitude thermal anomaly. Quantification of benthic communities revealed high coral cover (>70%, comprising three main morphospecies) prior to the bleaching event. Plating Montipora was most susceptible to bleaching, but in the plot where it was most abundant, coral cover did not change significantly because of post-bleaching increases in branching Acropora. In the other two plots, coral cover decreased while macroalgal cover increased markedly. Overall, coral cover declined from 73% to 59% over the course of the study, while macroalgal cover increased from 11% to 24%. The significant differences in impacts and post-bleaching trajectories among plots underline the importance of understanding the underlying causes of such variation to improve predictions of how climate change will affect reefs, especially at high-latitudes.
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, Australia; Australian Institute of Marine Science, PMB #3, Townsville MC, Townsville, QLD, Australia.
authors.forename: Tom C L
authors.initials: TC
authors.lastname: Bridge
authors.affiliation: School of Biological Sciences, University of Sydney, Sydney, NSW, Australia; Australian Centre for Field Robotics, School of Engineering, University of Sydney, Sydney, NSW, Australia.
authors.forename: Renata
authors.initials: R
authors.lastname: Ferrari
authors.affiliation: Australian Centre for Field Robotics, School of Engineering, University of Sydney, Sydney, NSW, Australia.
authors.forename: Mitch
authors.initials: M
authors.lastname: Bryson
authors.affiliation: School of Earth and Environment and Oceans Institute, University of Western Australia, Crawley, WA, Australia.
authors.forename: Renae
authors.initials: R
authors.lastname: Hovey
authors.affiliation: School of Biological Sciences, University of Sydney, Sydney, NSW, Australia.
authors.forename: Will F
authors.initials: WF
authors.lastname: Figueira
authors.affiliation: Australian Centre for Field Robotics, School of Engineering, University of Sydney, Sydney, NSW, Australia.
authors.forename: Stefan B
authors.initials: SB
authors.lastname: Williams
authors.affiliation: Australian Centre for Field Robotics, School of Engineering, University of Sydney, Sydney, NSW, Australia.
authors.forename: Oscar
authors.initials: O
authors.lastname: Pizarro
authors.affiliation: Marine Spatial Ecology Laboratory and ARC Centre of Excellence for Coral Reef Studies, School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia.
authors.forename: Alastair R
authors.initials: AR
authors.lastname: Harborne
authors.affiliation: School of Biological Sciences, University of Sydney, Sydney, NSW, Australia; School of Anatomy, University of Sydney, Sydney, NSW, Australia.
authors.forename: Maria
authors.initials: M
authors.lastname: Byrne
mesh_terms: D063147:Animal Distribution / Q000502:physiology*; D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D057231:Climate Change; D057894:Coral Reefs; D017753:Ecosystem; D012624:Seaweed / Q000502:physiology*; D013696:Temperature; D014904:Western Australia