Taxonomic patterns of bleaching within a South African coral assemblage

Floros, Camilla; Samways, Michael J.; Armstrong, B.

doi:10.1023/b:bioc.0000018151.67412.c7

Cited by 38 publications

(27 citation statements)

References 20 publications

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“…(Paulay and Benayahu 1999;Michalek-Wagner and Willis 2001), and Sarcophyton sp. (Floros andothers 2004, Strychar andothers 2005). Those species that are less effective at dispersal may also experience a decline.…”

Section: Latitudinal Expansion Of Coralsmentioning

confidence: 99%

Effects of Climate Change/Global Warming on Coral Reefs: Adaptation/Exaptation in Corals, Evolution in Zooxanthellae, and Biogeographic Shifts

Sammarco

Strychar

2009

Environmental Bioindicators

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Increased sea-surface temperatures (SSTs) associated with climate change/global warming have caused bleaching in scleractinian corals (the loss of obligate symbiotic zooxanthellae) on a global basis, resulting in mass mortality of corals and decimation of reefs. This symbiotic relationship makes these corals an excellent bioindicator of climate change.It has been hypothesized that bleaching is a mechanism by which corals can adapt to changing environmental conditions via the "shuffling" of symbiont clades and acquisition of better-adapted symbionts. Experimental research has confirmed that zooxanthellae are sensitive to increases in seawater temperatures, exhibiting apoptosis (a form of programmed cell death) at temperatures of ³30 o C while in situ. The coral hosts, however, tolerate experimental temperatures up to 34 o C, not showing signs of apoptosis and necrosis until 36 o C. Thus, zooxanthellae currently appear to be poorly adapted to temperature increases, while the corals are resistant to higher temperatures, indicating that they are either already adapted or exapted (previously termed preadapted) to such. Coral hosts are experiencing no mortality from increased temperatures but a great deal of mortality from the death of their zooxanthellar symbionts. Symbiodinium sp. has a short generation time of one to several days, vs. that of its host coral-one to several years, affording the symbionts a distinct advantage for adaptation. Mutation rates are low in micro-organisms and higher in larger organisms. Smaller organisms have a disproportionately higher mutation rate than larger organisms, however, when compared on a per-generation basis. Thus, zooxanthellae are positioned better to adapt more rapidly than their coral hosts. Zooxanthellae have numerous clades, some of which are suspected to be better-adapted to higher seawater temperatures than others. The discovery of new Symbiodinium clades may be due to our ability to detect them via better technology or due to mutation, adaptation, and directional selection. Changes in the frequency of occurrence of different clades betteradapted to higher temperatures may be due to the emergence of newly mutated strains (i.e., sub-clades or sub-types) or re-distribution of existing clades. Predictions for the future of coral reefs include the following: a) Some tropical corals may be lost to local or global extinction, based on species-specific susceptibility to temperature increases; b) it is unlikely that other symbionts such as cyanobacteria will be able to replace Symbiodinium in the host-symbiont relationship; c) the tropics and sub-tropics will expand poleward and the other climatic zones will shift poleward, at the expense of the polar and sub-polar zones; d) a new "hyper-tropical zone" may appear near the equator, within which corals may be less species diverse, ill represented, or absent; and e) the depth distribution of corals may be extended, but probably only nominally so.

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Section: Latitudinal Expansion Of Coralsmentioning

confidence: 99%

Effects of Climate Change/Global Warming on Coral Reefs: Adaptation/Exaptation in Corals, Evolution in Zooxanthellae, and Biogeographic Shifts

Sammarco

Strychar

2009

Environmental Bioindicators

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“…Bleaching may be minimal possibly because upwelling may create refugia for these reefs in times of increased sea-surface temperature (Riegl, 2003). Nevertheless, 2 to 3 years after the 1998 global mass bleaching event, certain corals in South Africa have begun to show some degree of bleaching (Floros et al, 2004). Meanwhile, the Spirobranchus loading on A. clathrata is high.…”

Section: Conservation Significance Of Resultsmentioning

confidence: 99%

Polychaete (Spirobranchus giganteus) loading on South African corals

Floros

Samways

Armstrong³

2005

Aquatic Conservation

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ABSTRACT1. Spirobranchus giganteus is a ubiquitous serpulid polychaete that is an obligate associate of living coral. At Sodwana Bay, South Africa, it is a conspicuous associate of Acropora clathrata plates.2. This study explores the relationship between S. giganteus abundance and factors hypothesized to represent stress to the corals, in particular coral bleaching, diving intensity and exposure to destructive wave action as a function of depth. In addition, plate size was investigated to increase understanding of habitat selection by S. giganteus.3. There was no significant correlation between diving intensity and S. giganteus abundance on the three reefs studied, suggesting either that the current level of diving intensity causes no stress or that S. giganteus does not indicate stress.4. Depth influenced the size distribution of A. clathrata plates, with the larger plates being at greatest depths (>0.4 m 2 at depths >14 m). Extremely high S. giganteus densities (most plates with number of individuals >50 m À2; maximum number of individuals 413.63 m À2 at 9 m depth on one reef) were recorded at depths >14 m, with density increasing overall with depth.6. The high densities of S. giganteus on A. clathrata plates are possibly because the plates are a physically elevated platform above the reef, where factors such as predation, competition and smothering by sand are far less important than on the reef surface. In turn, upwelling of nutrients and dependent plankton may encourage S. giganteus to maintain high population levels.7. Climatic or other stresses are not considered currently to be responsible for these high S. giganteus densities. Rather, the worm data reflect a healthy upwelling, which may change as the coral reef becomes stressed with global climate change.

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“…These issues are a concern for coral reef studies because species composition can vary widely between reefs or over time (Loya et al 2001, Somerfield et al 2008. Additionally, species have been observed to be variable in their susceptibilities to either disease (Gil-Agudelo & Garzón- (McField 1999, Marshall & Baird 2000, Floros et al 2004, Yee et al 2008.…”

Section: Discussionmentioning

confidence: 99%

“…However, it may not be correct to assume that all species within a single genus are equally susceptible to diseases (Aeby et al 2011). Similarly, species vary in their susceptibility to bleaching (McField 1999, Marshall & Baird 2000, Floros et al 2004, Yee et al 2008), yet models to predict bleaching events under elevated temperatures are typically derived from pooled observations of coral bleaching across taxa (Berkelmans et al 2004, Liu et al 2005, Maina et al 2008. Combining data across multiple host taxa may obscure independent disease trends (Lafferty et al 2004, Williams et al 2010.…”

Section: Introductionmentioning

confidence: 99%