Skeletal records of communitylevel bleaching in

Authors: Hannah C Barkley Anne L Cohen

Publish Date: 2016/07/25

Volume: 35, Issue: 4, Pages: 1407-1417

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Abstract

Tropical Pacific sea surface temperature is projected to rise an additional 2–3 °C by the end of this century driving an increase in the frequency and intensity of coral bleaching With significant global coral reef cover already lost due to bleachinginduced mortality efforts are underway to identify thermally tolerant coral communities that might survive projected warming Massive longlived corals accrete skeletal bands of anomalously high density in response to episodes of thermal stress These “stress bands” are potentially valuable proxies for thermal tolerance but to date their application to questions of community bleaching history has been limited Ecological surveys recorded bleaching of coral communities across the Palau archipelago during the 1998 and 2010 warm events Between 2011 and 2015 we extracted skeletal cores from living Porites colonies at 10 sites spanning barrier reef and lagoon environments and quantified the proportion of stress bands present in each population during bleaching years Across Palau the prevalence of stress bands tracked the severity of thermal stress with more stress bands occurring in 1998 degree heating weeks = 1357 °Cweek than during the less severe 2010 event degree heating weeks = 486 °Cweek Stress band prevalence also varied by reef type as more corals on the exposed barrier reef formed stress bands than did corals from sheltered lagoon environments Comparison of Porites stress band prevalence with bleaching survey data revealed a strong correlation between percent community bleaching and the proportion of colonies with stress bands in each year Conversely annual calcification rates did not decline consistently during bleaching years nor did annually resolved calcification histories always track interannual variability in temperature Our data suggest that stress bands in massive corals contain valuable information about spatial and temporal trends in coral reef bleaching and can aid in conservation efforts to identify temperaturetolerant coral reef communitiesThe authors thank Y Golbuu T DeCarlo GP Lohmann K Pietro K Karnauskas S Lentz D McCorkle A Shalapyonok D Ketten J Arruda S Cramer C MacDonald G Mereb A Merep M Kaplan and the staff of the Palau International Coral Reef Center for assistance with fieldwork and analyses This work was supported by a NSF Graduate Research Fellowship and a Next Wave Fellowship to H Barkley National Science Foundation award OCE1031971 the Dalio Foundation Inc through the Dalio Explore Fund Ray Dalio through the WHOI Access to the Sea Fund the Tiffany Co Foundation and the Nature Conservancy

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