Local conditions modulated the effects of marine heatwaves on coral bleaching in subtropical Hong Kong waters

Tzu Hao Chung, Walter Dellisanti, Keng Po Lai, Jiajun Wu, Jian Wen Qiu*, Leo Lai Chan*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

Abstract

A mass coral bleaching event occurred in the summer of 2022 in subtropical Hong Kong, driven by two marine heatwaves (MHWs) with high intensities of 1.56 and 0.86 °C above a mean climate condition, both MHWs 7 days with a short gap of 4 days during the strong La Niña year. A transect survey was conducted at nine study sites in three regions, which revealed widespread coral bleaching with bleached coral cover ranging from 2.4 to 70.3%. In situ environmental data revealed the presence of a thermocline and halocline. Local conditions, including depth and wave exposure, significantly influenced the bleaching response. Shallow-water (2–4 m) corals were primarily affected, particularly in sheltered and moderately sheltered sites that exhibited higher levels of bleached coral cover (42.97 ± 15.4% and 44.93 ± 29.4%, respectively) compared to the exposed sites (31.8 ± 5.2%). Bleaching in deep waters (4–6 m) was minimal, with only a few colonies of Goniopora at two of the three sheltered sites exhibiting bleaching (1.7 ± 1.5%). Heat stress resistance differed between coral genera. Recovery rate for four common coral genera is low for Acropora tumida. Additionally, a minor hypoxia event was found to cause mortality of non-coral benthos at a sheltered site (Sharp Island). These findings highlight the alarming impact of extreme heatwaves on subtropical coral communities and underscore the importance of monitoring coral bleaching.

Original languageEnglish
Pages (from-to)1235-1247
Number of pages13
JournalCoral Reefs
Volume43
Issue number5
Early online date26 Jul 2024
DOIs
Publication statusPublished - Oct 2024

Scopus Subject Areas

  • Aquatic Science

User-Defined Keywords

  • Coral bleaching
  • Halocline
  • Hong Kong
  • Marine heatwave
  • Thermocline
  • Wave exposure

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