The world’s southernmost fringing coral reef and extensive high-latitude coral and reef assemblages occur at Lord Howe Island (LHI) (31°33′S, 159°05′E) (Harriott et al. 1995). More than 80 scleractinian species have been recorded from LHI reefs, and these corals dominate much of the reef benthos (Harriott et al. 1995; Harrison 2008).
The first widespread coral bleaching event recorded at LHI occurred during the 1998 austral summer season when sea temperatures increased above 27°C (P. Harrison pers. obs.), but the bleaching had limited detectable impact on coral cover. During the 2010 summer season, sea temperatures around LHI were abnormally high and exceeded 28°C (~2–3°C above normal summer maximum), with an accumulated thermal stress of more than 19 degree heating weeks (http://coralreefwatch.noaa.gov). This thermal stress coincided with calm seas and high light penetration, resulting in the most extensive and severe coral bleaching event recorded at LHI to date (Fig. 1).
Bleached and partially bleached coral cover exceeded 90% at Sylph’s Hole and Comet’s Hole in the lagoon during March 2010, with less extensive and patchy bleaching at other reef sites around LHI. Pocilloporid corals (Stylophora, Pocillopora and Seriatopora) and Montipora spp. bleached more extensively than other corals, with some Porites, Isopora and other acroporid and faviid colonies, and host sea anemones, observed with substantial or partial pigmentation loss at some sites. Some bleaching-related coral mortality was evident during March 2010, with up to 25% of corals at Comet’s Hole having partial or complete bleaching-induced mortality.
Rising sea temperatures are predicted to induce more frequent coral bleaching events in future, leading to range shifts in reef corals to higher-latitude regions (Greenstein and Pandolfi 2008). However, this severe coral bleaching event at LHI demonstrates that even the highest latitude coral reef assemblages are also susceptible to bleaching stressors, which could limit future reef development and predicted range shifts to higher latitudes. Isolated reefs such as those at LHI, which lie more than 1,000 km south of the Great Barrier Reef, are likely to be slower to recover from severe disturbances due to their geographic and genetic isolation from other reefs that could potentially supply allochthonous coral larvae for recruitment (Harrison 2008).
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We thank I. Kerr and S. Gudge (LHI MPA), and B. Busteed (Howea Divers) for field and logistical support, and R. Berkelmans (AIMS) for temperature data. This study was funded by grants from Southern Cross University and NSW Marine Parks Authority.
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Harrison, P.L., Dalton, S.J. & Carroll, A.G. Extensive coral bleaching on the world’s southernmost coral reef at Lord Howe Island, Australia. Coral Reefs 30, 775 (2011). https://doi.org/10.1007/s00338-011-0778-7
- Coral Reef
- Great Barrier Reef
- Coral Cover
- Coral Bleaching Event
- Fringe Coral Reef