Nearshore turbid-zone corals exhibit high bleaching tolerance on the Great Barrier Reef following the 2016 ocean warming event

Morgan, Kyle M., Perry, Chris T., Johnson, Jamie a., and Smithers, Scott G. (2017) Nearshore turbid-zone corals exhibit high bleaching tolerance on the Great Barrier Reef following the 2016 ocean warming event. Frontiers in Marine Science, 4. 224.

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High sea surface temperatures (SSTs) on the Great Barrier Reef (GBR) during summer 2015/2016 caused extensive coral bleaching, with aerial and in-water surveys confirming high (but variable) bleaching-related coral mortality. In contrast, bleaching impacts on nearshore turbid-zone reefs, traditionally considered more "marginal" coral habitats, remain poorly documented. This is because rapid ecological surveys are difficult in these turbid water settings, and baseline coral community data from which to quantify disturbance are rare. However, models suggest that the extreme environmental conditions characteristic of nearshore settings (e.g., fluctuating turbidity, light, and temperature) may acclimate corals to the thermal anomalies associated with bleaching on offshore reefs, although validation by field evidence has to-date been sparse. Here we present a novel pre- (June 2013/2014) and post-warming (August 2016) assessment of turbid-zone coral communities and examine the response of corals to prolonged and acute heat stress within the Paluma Shoals reef complex, located on the central GBR. Our analysis of 2,288 still video frames (~1,200 m 2 ) which include 11,374 coral colonies (24 coral genera) suggest a high tolerance of turbid-zone corals to bleaching, with no significant changes in coral cover (pre: 48 ± 20%; post: 55 ± 26%) or coral community structure (e.g.,Acropora, Montipora, Turbinaria, Porites) following the warming event. Indeed, only one coral colony (Lobophyllia sp.) exhibited full colony bleaching, and just 1.5% of colonies displayed partial pigmentation loss ( < 20% colony surface). Taxa-specific responses to this thermal stress event contrast with clear-water assessments, as Acropora corals which are normally reported as highly susceptible to bleaching on clear-water reefs were least impacted at Paluma Shoals, a phenomena that has been observed within other turbid settings. Importantly, field surveys confirm regional SSTs were sufficiently high to induce coral bleaching (i.e., comparable number of degree heating days in nearshore and offshore areas), but bleaching severity was much higher at central GBR offshore sites. A more optimistic outlook than is generally offered for nearshore reefs on the central GBR may be implied by our results,which highlights the importance of these resilient but often overlooked coral reef habitats as potential refugia during climate-related disturbances.

Item ID: 54102
Item Type: Article (Research - C1)
ISSN: 2296-7745
Keywords: coral bleaching; environmental change; Great Barrier Reef; refugia hypothesis; turbid-zone; turbidity
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This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Funders: UK Natural Environment Research Council (NERC)
Projects and Grants: NERC urgency grant NE/P007694/1
Date Deposited: 15 Jun 2018 05:20
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4101 Climate change impacts and adaptation > 410102 Ecological impacts of climate change and ecological adaptation @ 50%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960304 Climate Variability (excl. Social Impacts) @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
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