Mass coral bleaching due to unprecedented marine heatwave in Papahānaumokuākea Marine National Monument (Northwestern Hawaiian Islands)

PLoS One. 2017 Sep 27;12(9):e0185121. doi: 10.1371/journal.pone.0185121. eCollection 2017.


2014 marked the sixth and most widespread mass bleaching event reported in the Northwestern Hawaiian Islands, home to the Papahānaumokuākea Marine National Monument (PMNM), the world's second largest marine reserve. This event was associated with an unusual basin-scale warming in the North Pacific Ocean, with an unprecedented peak intensity of around 20°C-weeks of cumulative heat stress at Lisianksi Island. In situ bleaching surveys and satellite data were used to evaluate the relative importance of potential drivers of bleaching patterns in 2014, assess the subsequent morality and its effects on coral communities and 3D complexity, test for signs of regional acclimation, and investigate long-term change in heat stress in PMNM. Surveys conducted at four island/atoll (French Frigate Shoals, Lisianski Island, Pearl and Hermes Atoll, and Midway Atoll) showed that in 2014, percent bleaching varied considerably between islands/atolls and habitats (back reef/fore reef and depth), and was up to 91% in shallow habitats at Lisianski. The percent bleaching during the 2014 event was best explained by a combination of duration of heat stress measured by Coral Reef Watch's satellite Degree Heating Week, relative community susceptibility (bleaching susceptibility score of each taxon * the taxon's abundance relative to the total number of colonies), depth and region. Mean coral cover at permanent Lisianski monitoring sites decreased by 68% due to severe losses of Montipora dilatata complex, resulting in rapid reductions in habitat complexity. Spatial distribution of the 2014 bleaching was significantly different from the 2002 and 2004 bleaching events likely due to a combination of differences in heat stress and local acclimatization. Historical satellite data demonstrated heat stress in 2014 was unlike any previous event and that the exposure of corals to the bleaching-level heat stress has increased significantly in the northern PMNM since 1982, highlighting the increasing threat of climate change to reefs.

MeSH terms

  • Animals
  • Anthozoa* / physiology
  • Climate Change
  • Conservation of Natural Resources*
  • Coral Reefs
  • Hawaii
  • Heat-Shock Response*
  • Islands*
  • Pacific Ocean*

Grant support

This study was supported by NOAA/NOS-HIMB agreement code MOA-2009-039 to provide salary to CSC, the STAR Fellowship Assistance Agreement no. FP-91768001-0 awarded by the US Environmental Protection Agency (EPA) to provide salary to JB. Funding was also provided by the ESPCoR Hawaiʻi (EPS-0903833) Track-I research grant to The University of Hawaii to provide salary to JB and KS, the NOAA Coral Reef Conservation Program to Coral Reef Watch to CME and the National Environmental Satellite, Data, and Information Service (NESDIS) for CME. This manuscript has not been formally reviewed by the EPA and the EPA does not endorse any products or commercial services mentioned in this publication. The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the authors and do not necessarily reflect the views of NOAA or the Department of Commerce. Global Science & Technology Inc. provided support in the form of salaries for GL, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of this author are articulated in the 'author contributions' section.