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

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
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