Sentinels of ocean acidification impacts survived Earth's last mass
extinction

Date:
September 28, 2020
Source:
University of Hawaii at Manoa
Summary:
Two groups of tiny, delicate marine organisms, sea butterflies
and sea angels, were found to be surprisingly resilient -- having
survived dramatic global climate change and Earth's most recent
mass extinction event 66 million years ago.



FULL STORY ==========================================================================
Two groups of tiny, delicate marine organisms, sea butterflies and
sea angels, were found to be surprisingly resilient -- having survived
dramatic global climate change and Earth's most recent mass extinction
event 66 million years ago, according to research published this week
in the Proceedings of the National Academy of Sciences led by Katja
Peijnenburg from Naturalis Biodiversity Center in the Netherlands.


==========================================================================
Sea butterflies and sea angels are pteropods, abundant, floating snails
that spend their entire lives in the open ocean. A remarkable example of adaptation to life in the open ocean, these mesmerizing animals can have
thin shells and a snail foot transformed into two wing-like structures
that enable them to "fly" through the water.

Sea butterflies have been a focus for global change research because
they make their shells of aragonite, a form of calcium carbonate that is
50 percent more soluble than calcite, which other important open ocean organisms use to construct their shells. As their shells are susceptible
to dissolving in more acidified ocean water, pteropods have been called "canaries in the coal mine," or sentinel species that signal the impact
of ocean acidification.

With some pteropods having thin shells and others having only partial
or absent shells, such as the sea angels, their fossil record is
patchy. Abundant pteropod fossils are only known from 56 million years
ago onward and mostly represent the fully-shelled sea butterflies. These observations led to the notion that evolutionarily, pteropods are a
relatively recent group of gastropods.

An international team of researchers sampled 21 pteropod species across
two ocean transects as part of the Atlantic Meridional Transect programme
and collected information on 2,654 genes. Analyzing these data and key
pteropod fossils, the scientists determined that the two major groups
of pteropods, sea butterflies and sea angels, evolved in the early
Cretaceous, about 139 million years ago.

"Hence, both groups are much older than previously thought and must have survived previous episodes of widespread ocean acidification, such as at
the end of the Cretaceous, 66 million years ago, and the Paleocene-Eocene Thermal Maximum, 56 million years ago," said Peijnenburg.

Knowing whether major groups of pteropods have been exposed to periods
of high carbon dioxide is important as researchers attempt to predict how various marine species may respond to current and future global change.

"Although these results suggest that open ocean, shelled organisms have
been more resilient to past ocean acidification than currently thought, it
is unlikely that pteropods have experienced global change of the current magnitude and speed during their entire evolutionary history," said
Erica Goetze, co- author and University of Hawai'i at M?noa oceanographer.

It is still an open question whether marine organisms, particularly those
that calcify, have the evolutionary resilience to adapt fast enough to
an increasingly acidified ocean.

"Current rates of carbon release are at least an order of magnitude higher
than we have seen for the past 66 million years," said Peijnenburg. Hence,
she stressed the disclaimer "past performance is no guarantee of future results."

========================================================================== Story Source: Materials provided
by University_of_Hawaii_at_Manoa. Original written by Marcie
Grabowski. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Katja T. C. A. Peijnenburg, Arie W. Janssen, Deborah Wall-Palmer,
Erica
Goetze, Amy E. Maas, Jonathan A. Todd, Ferdinand Marle'taz. The
origin and diversification of pteropods precede past perturbations
in the Earth's carbon cycle. Proceedings of the National Academy
of Sciences, 2020; 201920918 DOI: 10.1073/pnas.1920918117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200928093742.htm

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