Coral bleaching at Low Isles during the 1928–1929 Great Barrier Reef Expedition

Dunne, Richard P.; Brown, Barbara E.; Spencer, Tom; Woodworth, Philip L. ORCID: https://orcid.org/0000-0002-6681-239X. 2022 Coral bleaching at Low Isles during the 1928–1929 Great Barrier Reef Expedition. Coral Reefs, 41 (6). 1595-1610. 10.1007/s00338-022-02327-7

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Official URL: http://dx.doi.org/10.1007/s00338-022-02327-7

Abstract/Summary

The Great Barrier Reef Expedition (1928–1929) observed two of the earliest known examples of coral bleaching during a 13-month stay on Low Isles, northern Great Barrier Reef, Australia. The first was during austral summer in February 1929 in a shallow moat and the second during austral winter in June 1929 on a deeper seaward slope. Using Expedition records and modern analytical techniques, we geolocated previously undocumented photographs of bleaching and built a detailed picture of environmental conditions which show that the two episodes were driven by different proximate causes. The February bleaching coincided with highest annual seawater temperatures and Degree Heating Weeks, coupled with early afternoon aerial exposure leading to intense heating in tide pools and corals subjected to high solar insolation. Zooxanthellae densities would also have been at a seasonal low and the corals particularly susceptible to bleaching stress. In contrast in June, the seaward slope, normally submerged during the daytime, was aerially exposed to the afternoon sun and although seawater temperatures were 5 °C cooler than in the summer and despite relatively low sun altitudes and insolation in the winter, bleaching and mortality due to solar radiation was clearly visible on faces of exposed corals oriented towards the sun. Whilst reports of widespread temperature driven coral bleaching are commonplace today in an era of global warming, this paper demonstrates how similar environmental cues were involved a century ago and highlights the additional complexity of coral survival in the intertidal zone.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1007/s00338-022-02327-7
ISSN:	0722-4028
Date made live:	20 Mar 2023 13:00 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/534244

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1007/s00338-022-02327-7

ISSN:

0722-4028

Date made live:

20 Mar 2023 13:00 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/534244