Evolution after Chicxulub asteroid impact: Rapid response of life to end-cretaceous mass

Date:
July 14, 2020
Source:
Geological Society of America
Summary:
The impact event that formed the Chicxulub crater (Yucata'n
Peninsula, Me'xico) caused the extinction of 75% of species on
Earth 66 million years ago, including non-avian dinosaurs. One
place that did not experience much extinction was the deep, as
organisms living in the abyss made it through the mass extinction
event with just some changes to community structure.



FULL STORY ==========================================================================
The impact event that formed the Chicxulub crater (Yucata'n Peninsula,
Me'xico) caused the extinction of 75% of species on Earth 66 million years
ago, including non-avian dinosaurs. One place that did not experience much extinction was the deep, as organisms living in the abyss made it through
the mass extinction event with just some changes to community structure.


==========================================================================
New evidence from International Ocean Discovery Program (IODP) Expedition
364 of trace fossils of burrowing organisms that lived in the seafloor
of the Chicxulub Crater beginning a few years after the impact shows
just how quick the recovery of the seafloor ecosystem was, with the establishment of a well- developed tiered community within approximately 700,000 years after the event.

In April and May 2016, a team of international scientists drilled
into the Chicxulub impact crater. This joint expedition, organized
by the International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) recovered an extended syn-
and post-impact set of rock cores, allowing study of the effects of the
impact on life and its recovery after the mass extinction event. The
end Cretaceous (K-Pg) event has been profusely studied and its effect
on biota are relatively well-known. However, the effect of these changes
on the macrobenthic community, the community of organisms living on and
in the seafloor that do not leave body fossils, is poorly known.

The investigators concluded that the diversity and abundance of trace
fossils responded primarily to variations in the flux of organic matter
(i.e., food) sinking to the seafloor during the early Paleocene. Local
and regional-scale effects of the K-Pg impact included earthquakes of
magnitude 10-11, causing continental and marine landslides, tsunamis
hundreds of meters in height that swept more than 300 km onshore, shock
waves and air blasts, and the ignition of wildfires. Global phenomena
included acid rain, injection of aerosols, dust, and soot into the
atmosphere, brief intense cooling followed by slight warming, and
destruction of the stratospheric ozone layer, followed by a longer-term greenhouse effect.

Mass extinction events have punctuated the past 500 million years of
Earth's history, and studying them helps geoscientists understand how
organisms respond to stress in their environment and how ecosystems
recover from the loss of biodiversity. Although the K-Pg mass extinction
was caused by an asteroid impact, previous ones were caused by slower processes, like massive volcanism, which caused ocean acidification and deoxygenation and had environmental effects that lasted millions of years.

By comparing the K-Pg record to earlier events like the end Permian
mass extinction (the so-called "Great Dying" when 90% of life on Earth
went extinct), geoscientists can determine how different environmental
changes affect life. There are similar overall patterns of recovery after
both events with distinct phases of stabilization and diversification,
but with very different time frames. The initial recovery after the
K-Pg, even at ground zero of the impact, lasted just a few years; this
same phase lasted tens of thousands of years after the end Permian mass extinction. The overall recovery of seafloor burrowing organisms after
the K-Pg took ~700,000 years, but it took several million years after
the end Permian.


========================================================================== Story Source: Materials provided by Geological_Society_of_America. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Heather L. Jones, Sean P.S. Gulick, Timothy J. Bralower,
Christopher M.

Lowery, Francisco J. Rodri'guez-Tovar. Rapid macrobenthic
diversification and stabilization after the end-Cretaceous mass
extinction event.

Geology, 2020; DOI: 10.1130/G47589.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200714121748.htm

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