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Survival in freshwater environments during K-Pg impact "'winter"



From: Ben Creisler
bcreisler@gmail.com

A recent paper that may be of interest. The pdf is open access.

Douglas S. Robertson, William M. Lewis, Peter M. Sheehan & Owen B. Toon (2013)
K-Pg extinction patterns in marine and freshwater environments: The
impact winter model.
Journal of Geophysical Research: Biogeosciences (advance online publication)
DOI: 10.1002/jgrg.20086
http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20086/abstract

pdf:

http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20086/pdf

The Chicxulub asteroid impact produced massive extinction in
terrestrial environments most likely through an intense heat pulse and
subsequent widespread fires. Aquatic environments were shielded from
this heat and fire but nevertheless showed massive extinction in
marine environments and, for reasons unexplained, far less extinction
in freshwater environments. Extinction in marine environments resulted
from the effects of an “impact winter” caused by dust and smoke in the
atmosphere that extinguished sunlight at the Earth's surface for a
period of months to years. The resulting cessation of photosynthesis
caused a globally extensive extinction of phytoplankton taxa. Because
aquatic ecosystems, unlike terrestrial environments, are strongly
dependent on daily photosynthetic output by autotrophs, loss of
phytoplankton likely caused catastrophic mortality and extinction in
aquatic ecosystems. Other potential causes of mortality in aquatic
ecosystems include lower ambient temperatures and anoxia due to the
lack of photosynthetic oxygen. Inland waters, although probably
subject to high mortality, showed lower proportionate extinction than
marine environments probably because of the greater potential among
the freshwater taxa for dormancy, the greater efficiency of reaeration
by rapid flow to offset oxygen demand, abundant thermal refugia fed by
groundwater at moderate temperatures, and preadaptation of freshwater
taxa to a great degree of environmental variability. In addition,
detrital feeders appear to have had low extinction rates in either
marine or freshwater environments, but again freshwater taxa would
have been favored by higher renewal rates of detrital organic matter
as a result of their direct hydrologic contact with soil.