Discerning the timing and cause of historical mortality events in modern Porites from the Great Barrier Reef

Clark, Tara R.; Zhao, Jian‐xin; Roff, George; Feng, Yuexing; Done, Terence; Nothdurft, Luke D.; Pandolfi, John M.

doi:10.1016/j.gca.2014.04.022

Cited by 83 publications

(71 citation statements)

References 91 publications

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“…For example, H isotope ratios of leaf waxes now supplement dust, pollen, and charcoal proxies of paleo-aridity, and all can survive transport to marine basins, permitting those sediments to capture the climate of both the ocean and the adjacent airshed (64). Elemental data from corals can establish that mortality is associated with the stress of anomalously high rather than low sea temperatures and can test for changes in levels and drivers of mortality (66).…”

Section: Proxy Evidence Of (Paleo)environmentalmentioning

confidence: 99%

“…New field, laboratory, and calibration protocols have similarly enhanced other methods. Amino acid racemization dating is applicable to carbonate shells up to ∼1 Ma in cool waters and can yield decadal resolution within the Holocene; U-Th dating is applicable to corals, speleothems, and bones up to ∼500 ka and provides decadal resolution within the last few thousand years; and optically stimulated luminescence is applicable to mineral grains deposited in terrestrial settings up to several hundred thousand years with resolution ±5-10% (66,(68)(69)(70). Naturally occurring 210 Pb, which rains out rapidly from the atmosphere, remains a powerful method with approximately decadal resolution for sediments deposited within the past ∼150 y. Bomb-generated 137 Cs is becoming more difficult to detect owing to radioactive decay, but longer lived plutonium isotopes and their daughters produced at the same time can take its place as a global geochemical marker.…”

Section: Proxy Evidence Of (Paleo)environmentalmentioning

confidence: 99%

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Biology in the Anthropocene: Challenges and insights from young fossil records

Kidwell

2015

Proc. Natl. Acad. Sci. U.S.A.

127

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With overwhelming evidence of change in habitats, biologists today must assume that few, if any, study areas are natural and that biological variability is superimposed on trends rather than stationary means. Paleobiological data from the youngest sedimentary record, including death assemblages actively accumulating on modern land surfaces and seabeds, provide unique information on the status of present-day species, communities, and biomes over the last few decades to millennia and on their responses to natural and anthropogenic environmental change. Key advances have established the accuracy and resolving power of paleobiological information derived from naturally preserved remains and of proxy evidence for environmental conditions and sample age so that fossil data can both implicate and exonerate human stressors as the drivers of biotic change and permit the effects of multiple stressors to be disentangled. Legacy effects from Industrial and even pre-Industrial anthropogenic extirpations, introductions, (de)nutrification, and habitat conversion commonly emerge as the primary factors underlying the present-day status of populations and communities; within the last 2 million years, climate change has rarely been sufficient to drive major extinction pulses absent other human pressures, which are now manifold. Young fossil records also provide rigorous access to the baseline composition and dynamics of modern-day biota under pre-Industrial conditions, where insights include the millennial-scale persistence of community structures, the dominant role of physical environmental conditions rather than biotic interactions in determining community composition and disassembly, and the existence of naturally alternating states.biodiversity | ecology | conservation | paleobiology | paleoecology

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Section: Proxy Evidence Of (Paleo)environmentalmentioning

confidence: 99%

Section: Proxy Evidence Of (Paleo)environmentalmentioning

confidence: 99%

Biology in the Anthropocene: Challenges and insights from young fossil records

Kidwell

2015

Proc. Natl. Acad. Sci. U.S.A.

127

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“…A suite of element/Ca ratios in biological carbonate samples can be analysed rapidly using either inductively coupled plasma-mass spectrometry (ICP-MS) [e.g., Clark et al, 2014;, inductively coupled plasma-atomic emission spectrometry (ICP-AES)/inductively coupled plasma-optimal emission spectrometer (ICP-OES) [e.g., Flannery and Poore, 2013;, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) [e.g., Alibert and Kinsley, 2008;Fallon et al, 1999;Seo et al, 2013;Sinclair et al, 1998] or sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) [e.g., Quinn and Sampson, 2002]. Rapid analytical rates delivered by these techniques provide attractive throughput for paleoclimate reconstruction as they contrast sharply with the 20-30 minutes required to determine stable isotope ratios in a single sample using an isotope ratio mass spectrometer (IR-MS) [Quinn and Sampson, 2002].…”

Section: Trace Element Ratiosmentioning

confidence: 99%

“…Hence, the distribution of cements within a sample may be very heterogeneous. Cements are generally precipitated in microenvironments that may not reflect the chemistry of ambient seawater, as revealed by the presence of brucite and LMC in live coral skeletons [Buster and Holmes, 2006;Clark et al, 2014;Nothdurft et al, 2005]. The inclusion of exotic cements in geochemical samples therefore may bias the results significantly away from the ambient seawater conditions .…”

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confidence: 99%

Reef cores as records of Holocene water temperatures of the southern Great Barrier Reef: Geochemical analysis of traditional (Porites) and non-traditional (Acropora) reef building corals

Sadler¹

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In order to accurately predict future climate variations induced by natural and anthropogenic forcings, we require a detailed understanding of the Earth's climate system. With such temporally limited instrumental records, proxy-based reconstructions are an invaluable source of climate information. Current paleoclimate databases indicate a lack of records representing the southern hemisphere and tropics; key regions that can be represented by high resolution, coral geochemistry-based climate reconstructions.Reef coring techniques allow the recovery of significant proportions of coral material from throughout the Holocene, Pleistocene and beyond. Given the high species diversity of IndoPacific coral reefs, the presence of massive Porites commonly used for climate reconstruction is likely to be limited in reef cores. Corymbose Acropora, however, displays a high abundance in modern and fossil reef records and thus could act as a major source of new climate information from the Earth's recent history.Previous investigations of Acropora geochemistry have focused on branches, with significant levels of secondary thickening smoothing environmental signals otherwise recorded by the Sr/Ca ratio paleothermometer. This project investigates the potential of Acropora interbranch skeleton as a climate archive, following the identification of annual density banding patterns in computed tomography scans. Scanning electron microscopy based documentation of structure and growth patterns reveal that inter-branch skeleton is atypical for Acropora.Low linear extension rates, a simplified skeletal structure with limited secondary aragonite deposition, approximately horizontal density bands and seasonal cyclicity in Sr/Ca ratios bear a greater resemblance to massive corals such as Porites. These observations, combined with a high abundance in past and present Indo-Pacific reefs, suggest that inter-branch skeletal growth in Acropora may prove to be a valuable source of untapped paleoclimate information.A site-specific calibration for Acropora inter-branch skeleton Sr/Ca ratios to water temperature was conducted using modern corymbose Acropora colonies and concomitant instrumental water temperature records from the lagoon and fore-reef slope of Heron Reef, southern Great Barrier Reef (GBR). Large inter-colony differences in Sr/Ca ratios were observed in the modern cores, suggesting that inter-branch skeleton may not be a suitable archive for absolute temperature reconstruction. Normalisation of each Sr/Ca record to the corresponding core mean does, however, remove these inter-colony differences and allows the reconstruction of the seasonal water temperature amplitude with a sensitivity of −0.05 ii mmol/mol/°C. Application of the resulting transfer equation to the modern inter-branch skeleton Sr/Ca record successfully identified the greater seasonal temperature range of the lagoon compared to the adjacent reef slope. A site-specific calibration also was completed for southern GBR Porites at Heron Reef using the reef slope water te...

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“…non-radiogenic 230 Th is likely to be a mixture of two components each with its own isotopically distinct 230 Th/ 232 Th ratio: a hydrogenous (dissolved) and a detrital (particulate) component (Clark et al 2014b). These challenges highlight a clear requirement for a site-specific non-radiogenic 230 Th correction method for reliable dating of young coral samples from inshore coral reefs.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%