Abstract
Coral bleaching events have been increasing in frequency and severity worldwide. The most prolonged global bleaching event began in 2014 and continued into 2017 impacting more reefs than any previous occurrence. Here we present the results of coral bleaching and mortality surveys conducted in Kāneʻohe Bay Oʻahu, Hawaiʻi and compare them to the only other widespread bleaching events to impact the main Hawaiian Islands in 1996 and 2014. Results from these surveys along with associated environmental factors were used to compare these events to gain a baseline understanding of the physical processes that influence localized bleaching dynamics under these extreme environmental conditions. Survey results show extensive variation in bleaching (1996- 62%, 2014- 45%, 2015- 30%) and cumulative mortality (1996- <1%, 2014- 13%, 2015- 22%) between years. Bleaching prevalence was observed to decrease in certain reef areas across events, suggesting some acclimation and/or resilience, but possible increase susceptibility to mortality. Long-term monitoring sites show a similar temporal pattern of coral mortality and decline in coral cover, but revealed some reefs remained relatively un-impacted by consecutive high temperature events. Across the three bleaching events, we found that although circulation patterns can facilitate heating, the duration and magnitude of the high temperature event were found to be the primary forcing functions for coral bleaching and mortality. Other localized primary drivers influencing water temperature such as irradiance, turbidity, and precipitation contributed to spatial variations. Recovery and resilience of this coral reef ecosystem is dependent on many factors including duration and magnitude of heating, resulting mortality levels, localized environmental factors in the bay, and coral species affected and their bleaching tolerances.
Highlights
Coral reefs throughout the world are undergoing significant ecological decline due to climate change (Aronson et al, 2002; Gardner et al, 2005; Norström et al, 2009; De’ath et al, 2012)
Along with the rather unnatural history of Kane‘ohe Bay, these corals are currently living at temperatures (+1–2◦C) and acidification regimes that will not be experienced for decades on open coastal reefs across the Hawaiian Archipelago (Bahr et al, 2015b). To determine whether these conditions increase the susceptibility of these corals to future anthropogenic and climate change stressors, we investigated the response and recovery of this coral reef ecosystem from recent bleaching events
Results of the 2015 bleaching event showed the influence of water circulation and localized heating on coral bleaching and mortality patterns inside Kane‘ohe Bay
Summary
Coral reefs throughout the world are undergoing significant ecological decline due to climate change (Aronson et al, 2002; Gardner et al, 2005; Norström et al, 2009; De’ath et al, 2012). Increases in anthropogenic atmospheric gases mainly from fossil fuel burning have resulted in significant increases in global sea surface temperatures (SST) (Sabine et al, 2004). Increased SST have resulted in more severe and more frequent coral bleaching events worldwide. The offshore subtropical waters of the Hawaiian Islands have experienced heating over the past 58 years (+1.15◦C), which appears to have accelerated the frequency and severity of bleaching events throughout the archipelago (Hoeke et al, 2009; Bahr et al, 2015a). Recorded bleaching events (i.e., 1996, 2002, 2004) in the Hawaiian Archipelago were relatively short in duration and resulted in high recovery; reefs experienced unsurpassed bleaching on a statewide scale during the multi-year bleaching events in 2014 and 2015 (Bahr et al, 2015a)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
