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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 35 (2004), S. 523-556 
    ISSN: 1543-592X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: The evolutionary succession of marine photoautotrophs began with the origin of photosynthesis in the Archean Eon, perhaps as early as 3.8 billion years ago. Since that time, Earth's atmosphere, continents, and oceans have undergone substantial cyclic and secular physical, chemical, and biological changes that selected for different phytoplankton taxa. Early in the history of eukaryotic algae, between 1.6 and 1.2 billion years ago, an evolutionary schism gave rise to "green" (chlorophyll b-containing) and "red" (chlorophyll c-containing) plastid groups. Members of the "green" plastid line were important constituents of Neoproterozoic and Paleozoic oceans, and, ultimately, one green clade colonized land. By the mid-Mesozoic, the green line had become ecologically less important in the oceans. In its place, three groups of chlorophyll c-containing eukaryotes, the dinoflagellates, coccolithophorids, and diatoms, began evolutionary trajectories that have culminated in ecological dominance in the contemporary oceans. Breakup of the supercontinent Pangea, continental shelf flooding, and changes in ocean redox chemistry may all have contributed to this evolutionary transition. At the same time, the evolution of these modern eukaryotic taxa has influenced both the structure of marine food webs and global biogeochemical cycles.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 12 (2011): Q04003, doi:10.1029/2010GC003333.
    Description: Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and δ18O in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4°C and 13°C. This shallow infaunal species is primarily abundant in neritic to upper bathyal sediments (〈600 m). Both linear and exponential calibrations suggest a temperature sensitivity of ~12% per °C that is ~4 times higher than observed in other species of deep-sea benthic foraminifera. Culture experiments support the core top calibration. We find no discernible effect of salinity and saturation on Mg/Ca. Comparison between the measured benthic foraminiferal δ18O and predicted equilibrium values suggests that on average H. balthica δ18O is 0.64‰ ± 0.13‰ lower than predicted from the equilibrium composition. To test the reliability of using paired H. balthica Mg/Ca and δ18O measurements for reconstructing seawater δ18Osw and salinity, we apply this calibration to another depth transect from Cape Ghir off NW Africa, which was not included in the calibration. Based on error analysis of the calibration data and this validation test, we show that the uncertainty of reconstructing bottom water temperature and salinity from paired Mg/Ca and δ18O measurements of H. balthica is better than ±0.7°C and ±0.69 practical salinity scale, respectively. The small uncertainties allow for the reconstruction of seawater density to better than 0.3σθ units, which is precise enough for the identification of specific water masses and reconstruction of changes in their properties. We propose that the relatively high Mg content and temperature sensitivity of H. balthica might be due to minor, biologically mediated contribution of high-Mg calcite to the primarily low Mg calcite test, which is influenced by the ambient temperature. This hypothesis, if correct, suggests that benthic species with relatively high Mg/Ca may be better suited for deepwater temperature reconstructions than species that have thus far been more commonly used.
    Description: This project was funded by NSF Awards OCE 02‐20922 and 09‐02977 to YR, OCE 09‐28607 to MK, OCE02‐20776 to DWO, and DFG priority program INTERDYNAMIK to AM.
    Keywords: Mg/Ca ; Benthic foraminifera ; Temperature calibration ; Isotope
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2012-02-01
    Description: The Eocene-Oligocene transition (EOT; ca. 33–34 Ma) was a time of pronounced climatic change, marked by the establishment of continental-scale Antarctic ice sheets. The timing and extent of temperature change associated with the EOT is controversial. Here we present multiproxy EOT climate records (~15–34 k.y. resolution) from St. Stephens Quarry, Alabama, USA, derived from foraminiferal Mg/Ca, d18O, and TEX86. We constrain sea-surface temperatures (SSTs) in the latest Eocene and early Oligocene and address the issue of climatic cooling during the EOT. Paleotemperatures derived from planktic foraminifera Mg/Ca and TEX86 are remarkably consistent and indicate late Eocene subtropical SSTs of 〉28 °C. There was substantial and accelerated cooling of SSTs (3–4 °C) through the latest Eocene “precursor” d18O shift (EOT-1), prior to Oligocene Isotope-1 (Oi-1). Our multispecies planktic foraminiferal d18O records diverge at the E/O boundary (33.7 Ma), signifying enhanced seasonality in the earliest Oligocene in the Gulf of Mexico.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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