ORCID Profile
0000-0003-3003-5143
Current Organisations
Australian National University
,
Macquarie University
,
University of Adelaide
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Publisher: American Geophysical Union (AGU)
Date: 28-06-2019
DOI: 10.1029/2019GL083035
Publisher: Springer Science and Business Media LLC
Date: 04-03-2019
DOI: 10.1038/S41559-019-0806-5
Abstract: The dawn of animals remains one of the most mysterious milestones in the evolution of life. The fossil lipids 24-isopropylcholestane and 26-methylstigmastane are considered diagnostic for demosponges-arguably the oldest group of living animals. The widespread occurrence and high relative abundance of these biomarkers in Ediacaran sediments from 635-541 million years (Myr) ago have been viewed as evidence for the rise of animals to ecological importance approximately 100 Myr before their rapid Cambrian radiation. Here we show that the biosynthesis of 24-isopropylcholestane and 26-methylstigmastane precursors is common among early-branching unicellular Rhizaria-heterotrophic protists that play an important role in trophic cycling and carbon export in the modern ocean. Negating these hydrocarbons as sponge biomarkers, our study places the oldest evidence for animals closer to the Cambrian Explosion. Cambrian silica hexactine spicules that are approximately 535 Myr old now represent the oldest diagnostic sponge remains, whereas approximately 558-Myr-old Dickinsonia and Kimberella (Ediacara biota) provide the most reliable evidence for the emergence of animals. The proliferation of predatory protists may have been responsible for much of the ecological changes during the late Neoproterozoic, including the rise of algae, the establishment of complex trophic relationships and the oxygenation of shallow-water habitats required for the subsequent ascent of macroscopic animals.
Publisher: Norwegian Polar Institute
Date: 2018
Publisher: CSIRO Publishing
Date: 18-09-2023
DOI: 10.1071/MF23080
Publisher: Elsevier BV
Date: 10-2020
Publisher: Informa UK Limited
Date: 30-09-2021
Publisher: Informa UK Limited
Date: 15-10-2019
Publisher: Informa UK Limited
Date: 09-10-2023
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 12-2020
Publisher: Informa UK Limited
Date: 09-10-2019
Publisher: Biodiversity Heritage Library
Date: 26-05-1976
DOI: 10.5962/P.361053
Publisher: Springer Science and Business Media LLC
Date: 24-10-2022
Publisher: American Geophysical Union (AGU)
Date: 19-01-2017
DOI: 10.1002/2016JD025737
Publisher: Informa UK Limited
Date: 28-03-2021
Publisher: Cambridge University Press (CUP)
Date: 13-04-2021
DOI: 10.1017/QUA.2021.12
Abstract: Northern and southern hemispheric influences—particularly changes in Southern Hemisphere westerly winds (SSW) and Southern Ocean ventilation—triggered the stepwise atmospheric CO 2 increase that accompanied the last deglaciation. One approach for gaining potential insights into past changes in SWW/CO 2 upwelling is to reconstruct the positions of the northern oceanic fronts associated with the Antarctic Circumpolar Current. Using two deep-sea cores located ~600 km apart off the southern coast of Australia, we detail oceanic changes from ~23 to 6 ka using foraminifer faunal and biomarker alkenone records. Our results indicate a tight coupling between hydrographic and related frontal displacements offshore South Australia (and by analogy, possibly the entire Southern Ocean) and Northern Hemisphere (NH) climate that may help confirm previous hypotheses that the westerlies play a critical role in modulating CO 2 uptake and release from the Southern Ocean on millennial and potentially even centennial timescales. The intensity and extent of the northward displacements of the Subtropical Front following well-known NH cold events seem to decrease with progressing NH ice sheet deglaciation and parallel a weakening NH temperature response and litude of Intertropical Convergence Zone shifts. In addition, an exceptional poleward shift of Southern Hemisphere fronts occurs during the NH Heinrich Stadial 1. This event was likely facilitated by the NH ice maximum and acted as a coup-de-grâce for glacial ocean stratification and its high CO 2 capacitance. Thus, through its influence on the global atmosphere and on ocean mixing, “excessive” NH glaciation could have triggered its own demise by facilitating the destratification of the glacial ocean CO 2 state.
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 07-2022
Publisher: Magnolia Press
Date: 04-02-2022
DOI: 10.11646/ZOOTAXA.5094.3.1
Abstract: Details of the post-embryonic development of two Notodromadidae species, Notodromas trulla Smith & Kamiya, 2014 and Newnhamia fenestrata King, 1855, (subfamily Notodromadinae) are provided, and compared with previous ontogenetic studies on other podocopid families and superfamilies. The ontogenetic development is generally similar to other families, consisting of eight free-living juvenile stages and one adult stage, but the first instar, with a leg-like mandible, resembles that of the Cyprididae, rather than other families. From the A-7 instar onwards, the ventral margin of the carapace is a flattened ovoid, and the dorsolateral eye cups are separated, resembling those of the adults, suggesting that a neustonic lifestyle, similar to that of the adults, is embraced from a very early age. In addition to the ventral margin, other apomorphies of the Notodromadinae include spur-like protrusions on the walking legs of juveniles, which become reduced in adults, and features of the mandibles, probably related to neustonic feeding. Overall, Ne. fenestrata has more plesiomorphic features than No. trulla, and most differences between the two species are related to sexually selected characters, such as different sexually dimorphic features of the antennae. This suggests that sexual selection has been the main evolutionary driving force causing morphological ergence in the subfamily. The two taxa, one from Japan (No. trulla), the other Australia (Ne. fenestrata), have perhaps been separated since the breakup of Pangaea, which started in the Middle Jurassic. This suggests that despite the long geographical isolation, many aspects of ostracod anatomy have remained unchanged over long periods of time. On reviewing the taxonomy of the family, we conclude that monophyly needs to be confirmed with further work, and the subfamily Notodromadinae can be ided into two groups: the Notodromas-group and the Newnhamia-group.
Publisher: Springer Science and Business Media LLC
Date: 29-06-2016
Publisher: Springer Science and Business Media LLC
Date: 10-08-2023
DOI: 10.1038/S41467-023-40452-1
Abstract: Reconstructions of ocean oxygenation are critical for understanding the role of respired carbon storage in regulating atmospheric CO 2 . Independent sediment redox proxies are essential to assess such reconstructions. Here, we present a long magnetofossil record from the eastern Indian Ocean in which we observe coeval magnetic hardening and enrichment of larger, more elongated, and less oxidized magnetofossils during glacials compared to interglacials over the last ~900 ka. Our multi-proxy records of redox-sensitive magnetofossils, trace element concentrations, and benthic foraminiferal Δδ 13 C consistently suggest a recurrence of lower O 2 in the glacial Indian Ocean over the last 21 marine isotope stages, as has been reported for the Atlantic and Pacific across the last glaciation. Consistent multi-proxy documentation of this repeated oxygen decline strongly supports the hypothesis that increased Indian Ocean glacial carbon storage played a significant role in atmospheric CO 2 cycling and climate change over recent glacial/interglacial timescales.
No related grants have been discovered for Patrick De Deckker.