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No state change in pelagic fish production and biodiversity during the Eocene-Oligocene Transition


Sibert, Elizabeth; Zill, Michelle; Frigyik, Ella; Norris, Richard (2020), No state change in pelagic fish production and biodiversity during the Eocene-Oligocene Transition, Dryad, Dataset,


The Eocene-Oligocene (E/O) boundary ~33.9 million years ago, has been described as a state change in the Earth system marked by the permanent glaciation of Antarctica and a proposed increase in oceanic productivity. Here we quantified the response of fish production and biodiversity to this event using microfossil fish teeth (ichthyoliths) in seven deep-sea sediment cores from around the world. Ichthyolith accumulation rate (a proxy for fish biomass production) shows no synchronous trends across the E/O. Ichthyolith accumulation in the Southern Ocean and Pacific Gyre sites is an order of magnitude lower than the equatorial and Atlantic sites, demonstrating that the Southern Ocean was not a highly productive ecosystem for fish before or after the E/O. Further, tooth morphotype diversity and assemblage composition remained stable across the interval, indicating little change in the biodiversity or ecological role of open ocean fish. While the E/O boundary was a major global climate change event, its impact on pelagic fish was relatively muted. Our results support recent findings of whale and krill diversification which suggest that the pelagic ecosystem restructuring commonly attributed to the E/O transition likely occurred much later, in the late Oligocene or Miocene.

Usage Notes

README for Data Archive for:
Pelagic fish production and diversity unchanging across the Eocene-Oligocene Glaciation
Elizabeth C Sibert, Michelle E Zill, Ella T. Frigyik, and Richard D Norris

Contact: Elizabeth Sibert ( *Email address will be updated at a future time

This dataset consists of images of each unique ocean drilling sample considered in this study.

There are two sites included in this study: DSDP Site 596 and ODP Site 689.
They were imaged at different times and on different instruments, however the data are functionally equivilant.

File Name information:

ODP Site 689: Filenames take the form:
ODP-689B    ANT01        001         10H        1W           10-13cm                N1of2        z200x
Imaged on a Keyence Digital Microscope System at Harvard University, using the Museum of Comparative Zoology's Digital Imaging Facilities
Tooth IDs are in Table S20 from supplemental Dataset Excel spreadsheet

DSDP Site 596: Filenames take the form:
DSDP-596     P031        M20          2H        5W           116-118cm                g106        Hwell      N1of1    Mcompount_Oflat_I1  TzEDF-0    X5
Imaged on a Leica Microscope automated imaging system in the Pincelli Hull Laboratory at Yale University.
Tooth IDs are in Table S19 from supplemental Dataset Excel spreadsheet

SiteNumber - ODP-689B is consistent throughout
SlideNumber - an internal numbering system to identify which physical four-hole micropaleontology slide the sample is archived on
SampleNumber - An internal serial numbering to aid in identification of specific samples. (Multiple samples are often archived on the same slide, but in different holes)
IODP-Core, IODP-Setion, and IODP-SampleDepthInterval - External unique IODP Sample identifier information identifying precisely what depth in the hole hte sample is from.
HoleNumber - Some samples have multiple holes on the slide designated to them, this identifies which hole was imaged.
    Throughout this project, only teeth >63um were identified, so all hole numbers are N1of2; N2of2 is reserved for teeth <63um, which were not included in this study.
ZoomLevel - refers to the zoom lens reading on the Keyence microscope; unique to ODP 689; 0.95 um/pixel
SizeFraction - unique to DSDP 596, this is objects >106um
SlideType - unique to DSDP 596, Hwell refers to "4-well slide"
MicroscopeSettings - unique to DSDP 596, refers to the microscope used to image the objects, a piece of metadata included by this imaging system
ImageType - TzEDF refers to "extended depth of focus" - while this is unique to DSDP 596 filenames, all images included in this study are extended depth of focus images
ZoomLens - Refers to the lens used on the Leica microscope; Unique to DSDP 596; 0.98 um/pixel

For each sample, we include the following:

1) A full-slide, medium-resolution image of all microfossils found in the discrete sediment sample,
    with red "segment" boxes around each object found by our microfossil image-segmenting software
2) "Segmented" images (directory name is 'focused') at full-resolution. Note that for many of these
    samples, there are a number of identified 'segmented' boxes that are not of teeth, but which
    picked up reflections from the slides or other imperfections. We have included these images for
    transparency. We have also included the images of shark denticles, which were included in the
    total ichthyolith counts, but not identified to morphotype or included in diversity analyses.


Harvard University Milton Fund