Rising atmospheric CO2 concentrations threaten coral reefs worldwide by causing ocean warming and acidification. When seawater temperatures are unusually high, corals lose a significant portion of their vital algal endosymbionts and/or photosynthetic pigments making them appear pale or white – a process referred to as coral bleaching. As corals get most of their carbon from the algal endosymbionts, the breakdown of this symbiosis significantly weakens coral and can lead to widespread mortality if bleaching is severe. Bleaching events have been predicted to become annual events sometime later this century. Despite this knowledge, the impacts of annual bleaching on coral physiology, biogeochemistry, and overall resilience remain largely unknown. For the first time, annually recurring bleaching was simulated on ecologically relevant timescales by subjecting three Caribbean coral species (Orbicella faveolata, Porites astreoides, and Porites divaricata) to experimental coral bleaching (+1°C for 2.5 weeks) in two consecutive years. Impacts on their physiology and biogeochemistry were assessed in great detail immediately after repeat bleaching as well as after short and long term recovery. We show that repeat bleaching can dramatically alter thermal tolerance of the coral holobiont (i.e., animal host and endosymbiont). Species such as P. divaricata will be able to rapidly acclimate to frequent temperature stress and persist on future coral reefs, whereas others such as P. astreoides will show increasing bleaching susceptibility and may thus face significant decline.
Physiology and biogeochemistry of corals subjected to repeat bleaching and combined ocean acidification and warming
Published 13 February 2014 Science ClosedTags: biological response, calcification, corals, laboratory, multiple factors, physiology, temperature
