||June 14, 2001
GSA Release No. 01-18
Scientists Share Multidisciplinary Discoveries at "Earth System Processes"
(II) Session Highlights
- SESSION 23: Tuesday, June 26.
ARCHEAN EARTH AND CONTEMPORARY LIFE: THE TRANSITION FROM AN ANAEROBIC TO AN
AEROBIC MARINE ECOSYSTEM
Session 30 Abstracts ]
- Can you imagine our world being devoid of oxygen for almost half of its history?
And suddenly there's an abrupt rise at ~2 ga? This amazing picture of our
Earth is finding increasing support from rock record geologic data.
- "But what intrigues physical and biological scientists alike is 'why the rise
and why at ~2 ga'?" remarked Janet Siefert, co-chair for this session. Siefert
is a molecular evolutionist at Rice University in Houston, Texas.
- "We know with increasing certainty from geologic biomarkers, fossils, and
molecular phylogenies that the organisms most likely responsible for this rise,
the ubiquitous cyanobacteria or their ancestors, were surely present at least
half a million years prior to the rise. So why the lag?"
- The rise of oxygen is a great science question. It is unique because there
are as many theories that postulate the event as dominated by physical processes
as there are ones that predict it was a biologically mediated phenomenon. This
session will bring oceanographers, genome analysts, and geoscientists with their
competing theories, together in one venue with the hopes that a more substantive
and accurate picture of what may have actually occurred can be brought to the
- The newest discoveries are coming from papers that are multidisciplinary
- David Catling, from the Space Science Division of the NASA Ames Research
Center and the SETI Institute, will build on the idea that the Archean atmosphere
was dominated by methane as the primary greenhouse gas, but expands it to include
an explanation for the oxidation of Earth. He postulates that the kinetic effects
of oxygen and methane are reversed from today; in effect hydrogen escape to space
was inescapable and oxygenation of the atmosphere was irreversible.
- Christian J. Bjerrum, Danish Center for Earth System Science at the
University of Copenhagen, will postulate that due to the limited availability
of phosphorous, a principle nutrient in limiting carbon production, photosynthesis
was depressed in cyanobacteria during the Archean and early Proterozoic.
- Christopher House, a microbial geobiologist from Pennsylvania State
University, will provide further evidence for a newly discovered archaeal bacterial
lineage that consumes methane anaerobically. He gathered this evidence using FISH
and iron microbe techniques to measure carbon isotope depletion.
- Martin Brasier, Earth Sciences at the University of Oxford, will provide
a new look at whether or not morphological remains of fossils thought to be photosynthetic
are as old as previous estimates have stipulated. This is important as it is some
of the most quoted evidence for the antiquity of oxygenic photosynthesis.
- Janet Siefert will present data that uses some of the most basic molecules
for biochemistry, iron-sulfur clusters, to determine the sequence of metabolic
events that may have occurred in the Archean timeframe.
- George Fox, Department of Biology and Biochemistry at the University
of Houston, will give a genomic perspective of what the Archean contemporary cyanobacteria
must have contained as its genomic component. This is an important piece of molecular
evidence that can be compared to the morphological fossil record and the proposed
atmospheric conditions prior to the rise of oxygen.
- SESSION 24: Tuesday, June 26.
CONTROLS ON PHANEROZOIC DIVERSIFICATIONS AND EXTINCTIONS: LONG-TERM INTERACTIONS
BETWEEN THE PHYSICAL AND BIOTIC REALMS
- In this session, scientists from the USA and the UK will explore what controls
the long-term patterns of origination and extinction that give shape to the history
of life and how life itself has participated in that process. This connects directly
to contemporary concerns with biodiversity issues and questions about the effects
of climate change. For example: What natural processes have caused past climate
shifts and mass extinction episodes?
- By examining the records of climate changes over the past 600 million years,
what caused the changes, and what effects they had on ancient organisms, these
scientists are discovering what implications this information has for understanding
- The most important general themes of the papers in this session are: (1) the
adoption of a systems approach to the understanding of Earth's history (major
events being caused by multiple, independent factors) and (2) the significance
of 'feedback mechanisms.'
- Some of the highlights are as follows:
- Session co-chair Norman MacLeod will begin by taking a look at the
identifying controls on Phanerozoic extinction and diversification patterns. (MacLeod
is the Associate Keeper in the Department of Palaeontology at The Natural History
Museum in London.) Patterns of biodiversification and extinction over the last
250 million years show evidence of having been controlled by multiple factors,
especially the interplay between tectonic processes (e.g., volcanism, sea-level
change), and the evolutionary history of primary producer lineages (e.g., phytoplankton
and land plants).
- Doug Erwin, from the Department of Paleobiology at the Smithsonian
Institution, will explain how the biodiversity increase that characterizes the
biotic recovery from a mass extinction event is structured by ecological factors
to a larger extent than previously thought.
- Paul Wignall, Earth Sciences Department at the University of Leeds,
has discovered that the relationship between mass extinction events and large
volcanic eruptions is complex and likely involves climate forcing factors other
than the eruption itself, including the presence of life forms (e.g., phytoplankton)
that collectively possess the ability to buffer the global climate from short-term
- Geerat Vermeij, from the Department of Geology at the University of
California, Davis, will consider how patterns of ecological feedback between herbivores
and carnivores that result in a progressive intensification of nutrient recycling
in the oceans have been a dominant theme in the history of life and have exerted
an important 'top-down' (as opposed to bottom-up) evolutionary and ecological
- SESSION 28: Tuesday, June 26.
ANTHROPOGENIC MODIFICATIONS TO THE EARTH SYSTEM
Poster Session 27 abstracts ]
- The human presence on Earth has greatly impacted the environment for better
or worse. Geoscientists in this session will consider a wide variety of evidence
for the nature, magnitude, and implications of human impact on our planet for
the past, present, and future.
- Fred T. Mackenzie, Professor of Sedimentary and Global Geochemistry
from the Department of Oceanography at the University of Hawaii, will begin the
session by looking at how human activities influenced the biogeochemical cycles
of carbon, phosphorus, and nitrogen in the surface of the Earth since 1840. This
will be quite interesting for those who would like to know what the unperturbed
Earth system was like, and who also want to understand the fate of these elements
through projections to the year 2040.
- Timothy M. Lenton, Centre for Ecology and Hydrology at the Edinburgh
Research Station, will speak about positive feedbacks in the global carbon cycle
that may make it more difficult for the oceans and atmosphere to absorb anthropogenic
CO2 in the future.
- Gary Hughes, from Raytheon Santa Barbara Remote Sensing in California,
will talk about a direct, empirical correlation between atmospheric CO2
and land temperature measurements that indicates a strong greenhouse warming effect:
5 degrees Celsius for CO2 doubling.
- Berry Lyons, Department of Geological Sciences and Byrd Polar Research
Center at the Ohio State University, will take a look at how urbanization--specifically
in Atlanta, Georgia and Columbus, Ohio--affects water quality in local rivers.
He will note the similarity of increased concentrations of elements in the Chattahoochie
River downstream from Atlanta, Georgia, with those observed for the Seine River
as it passes through metro Paris. (Yet the Scioto River in the Columbus, Ohio,
metro area, shows little urban influence.) The urban "footprint" in various areas
in the United States and Europe has made quite an impact on the water quality
of rivers downstream from major urban centers.
- SESSION 36: Wednesday, June 27.
ROLE OF HYDROTHERMAL SYSTEMS IN BIOSPHERIC EVOLUTION
Poster Session 40 Abstracts ]
- Hydrothermal environments are unique because they offer a potentially widespread
habitat for life both on the early Earth, and elsewhere in the Solar System. The
study of hydrothermal systems provides a doorway into the early history of life
and allows us to better understand the origins of our biosphere, its history,
and place in the universe. This session will provide an updated overview of the
field and will serve as a forum to report its cutting-edge science.
- "I think one of the most intriguing things about hydrothermal systems is that
they teem with life at temperatures far exceeding what humans would consider viable,"
said session co-chair Jack Farmer. Farmer is an astrobiologist and geologist
at Arizona State University.
- "They also harbor many unusual organisms and unique metabolic strategies.
Some of the organisms found living at the highest temperatures appear to be very
primitive forms, close to a last common ancestor of life. These forms are able
to exist on inorganic by-products derived from the aqueous weathering of rocks."
Not requiring sunlight for their metabolism, nor organic inputs from other organisms,
these "chemoautotrophic" (chemically-based) forms provide models for the kinds
of organisms that could exist in subsurface environments of Mars, Europa, and
- Hydrothermal systems are also very interesting places to explore for novel
organisms and their metabolic processes of interest to biotechnology. "The famous
example of PCR (polymerase chain reaction), a genetic process whereby even tiny
sequences of a genome can be cloned and amplified, was discovered in a Yellowstone
hot spring," Farmer explained. "This discovery revolutionized molecular biology
and spawned a multi-billion dollar industry."
- Franco Piranjo (Geological Survey of Western Australia) will present
an overview on the nature of hydrothermal environments and Anna Louise Reysenbach
(Portland State University) will provide an overview of their microbiology.
- Mike Russell, from the Isotope Geoscience Unit at the Scottish Universities
Environmental Research Centre, also co-chairs the session and will present a talk
on hydrothermal systems as a potential cradle for early prebiotic chemistry and
- Sherry Cady, Geology Department at Portland State University, will
review what we have learned about life near its upper temperature limit.
- Tullis Onstott, from the Department of Geosciences at Princeton, will
discuss the exploration for a deep, hot microbial biosphere in deep gold mines
in South Africa.
- Malcolm Walter, Australian Centre for Astrobiology at Macquariue University,
will talk about a variety of fossil biosignatures in billion-year-old-plus deep-sea
vent deposits in Australia.
- Beda Hofmann, from the Natural History Museum in Bern, Switzerland,
will review a newly-discovered fossil record of deep subsurface life found in
- These subsurface talks hold special importance in opening up new opportunities
to explore for life on the early Earth and elsewhere in the Solar System.
- Finally, Martin Van Kranendonk, Geological Survey of Western Australia,
will describe hydrothermal environments associated with the oldest previously-reported
cellular fossils (~3.5 billion years) from Australia.
- In the poster session, Meredith Payne (Arizona State) will present
a review of the prospects for hydrothermal life on Mars, focusing special attention
on polar regions where volcanoes appear to have recently interacted with and melted
polar ice, sustaining recent liquid water habitats near the surface. The Mars
sites she will review are considered important potential candidates for future
landed missions to Mars.
Other noteworthy sessions include:
- Session 8: Monday, June 25.
FRAGILE AND HAZARDOUS ENVIRONMENTS
[ View Abstracts ]
[ View Poster Session 7 Abstracts ]
- Session 10: Monday, June 25.
THE ROLE OF NATURAL GAS HYDRATES IN THE EVOLUTION OF PLANETARY BODIES AND LIFE
[ View Abstracts ]
[ View Poster Session 11 Abstracts ]
- Session 42: Wednesday, June 27.
FLUID SEEPS AND SHALLOW MIGRATION PHENOMENA AT CONTINENTAL MARGINS: IMPACTS SPANNING THE LITHOSPHERE, BIOSPHERE, AND HYDROSPHERE
[ View Abstracts ]
[ View Poster Session 43 Abstracts ]