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Northeastern Geobiology
Symposium 2017
University of Connecticut, Center for Integrative
Geosciences
Northeastern Geobiology Symposium 2017
University of Connecticut, Center for Integrative Geosciences
~ Breakfast and coffee, 8.00 - 9.00 am~
Student’s Union, Room 330/331
Oral Session 1: 9.00 - 10:20am, Student’s Union Lecture Theater
9.00 - 9.15
Introduction
9.15-9.30
William Leavitt, Dartmouth College: Lipid H-isotopic ratios from anaerobic
bacteria record past energetic state.
9.30 - 9.45
Romain Darnajoux, Princeton University: A glimpse at the lichen symbiosis:
from metal homeostasis to ecosystems function.
9.45 - 10.00
Michael Henehan, Yale University: How strange was the Strangelove Ocean?
10.00 - 10.35
KEYNOTE: Paul Olsen, Lamont Doherty Earth Observatory, Columbia
University: Fire and Ice: Changing views and biases of mass extinction.
~ Coffee break, 10:35 - 11.15 am ~
Student’s Union, Room 330/331
Oral Session 2: 11.15am - 12.35pm, Student’s Union Lecture Theater
11.15 - 11.30
Rosa Zayas, University of Delaware: Deep life at the Tonga Trench: a
metagenomic perspective from the subsurface ocean to 2 meters below the sea
floor.
11.30-11.45
Eli Moore, Rutgers University: Metal availability and the evolution of Archean
metabolisms.
11.45-12.00
Marjorie Cantine, Massachusetts Institute of Technology: Environmental
adaptation from the origin of life to the last universal common ancestor.
12.00 - 12.35
KEYNOTE: Jennifer Biddle, University of Delaware: Sequencing the
subsurface: Microbes in the marine deep biosphere.
~ Lunch, 12:35 - 2.00pm ~
Student’s Union, Room 330/331
1
Oral Session 3: 2.00pm - 3.20pm, Student’s Union Lecture Theater
2.00 - 2.15
Katja Luxem, Princeton University: A role for the alternative V-nitrogenase in
redox homeostasis.
2:15 - 2.30
Benjamin Jelen, Rutgers University: Revealing the genes responsible for sulfur
respiration in Thermovibrio ammonificans.
2.30 - 2.45
Danielle Ramos, Princeton University: Potassium isotopic composition of marine
and freshwater fish: An example of diffusive K fractionation in biological
systems.
2.45 - 3.20
KEYNOTE: Noah Planavsky, Yale University: Metal isotopes in Geobiology .
~ Coffee break, 3.20 - 4.00pm ~
Student’s Union, Room 330/331
Oral Session 4: 4.00pm - 5.00pm, Student’s Union Lecture Theater
4.00 - 4.15
Clara Blättler, Princeton University: An independent constraint on marine sulfate
levels in the Ediacaran-Cambrian transition.
4.15 - 4.30
Luke Faggetter, Smith College/University of Leeds: Mercury spikes in the
Cambrian Series 2 - 3 boundary: an imprint of the Kalkarindji LIP?
4.30 - 4.45
Qin Leng, Bryant University: A non-toxic and inexpensive histological
microtechnique for biological and paleobiological research.
4.45 - 5.00
Greg Fournier, Massachusetts Institute of Technology: A phylogenetic signal for
Paleoproterozoic reorganisation of the global sulfur cycle.
Poster session: 5.00 - 8.00pm, Student’s Union Room 330/331
Conference dinner, 6.30 - 8.00pm
Student’s Union, Room 330/331
~ Close ~
2
Table of Contents
Abstracts for Oral Presentations
Lipid H-isotopic ratios from anaerobic bacteria record past energetic state
8
William D. Leavitt, Theodore M. Flynn, Sean J.L. Murphy, Melanie Suess, Lee Lynd, and
Alexander S. Bradley
A glimpse at the lichen symbiosis; from metal homeostasis to ecosystems function
9
Romain Darnajoux, Xinning Zhang, Darcy McRose, Jolanta Miadlikowska, François Lutzoni,
Anne M. L. Kreapiel and Jean-Philippe Bellenger
How strange was the Strangelove Ocean?
10
Michael J. Henehan, Andy Ridgwell, Ellen Thomas, Shuang Zhang, Noah J. Planavsky, Laia
Alegret, Daniela N. Schmidt, James W. B. Rae, Gavin L. Foster, Brian T. Huber and Pincelli
M. Hull.
Deep life at the Tonga Trench: A metagenomic perspective from the surface ocean to 2
meters below the sea floor
11
Rosa Leon Zayas, Douglas H. Bartlett, and Jennifer F. Biddle
Metal Availability and the Evolution of Archean Metabolisms
12
Eli Moore, Benjamin I. Jelen, Donato Giovannelli, Hagai Raanan, and Paul G. Falkowski
Environmental Adaptation from the Origin of Life to the Last Universal Common
Ancestor
13
Marjorie Cantine and Gregory P. Fournier
A role for the alternative V-nitrogenase in redox homeostasis
14
Katja Luxem, Carol C. Chui, Anne M.L. Kraepiel, and Xinning Zhang
Revealing the genes responsible for sulfur respiration in Thermovibrio ammonificans
15
Benjamin Jelen, Donato Giovannelli, and Costantino Vetriani
Potassium isotopic composition of marine and freshwater fish: An example of diffusive K
fractionation in biological systems
16
Danielle Santiago Ramos and John A. Higgins
An independent constraint on marine sulfate levels at the Ediacaran–Cambrian transition
17
Clara Blättler, Kristin Bergmann, John Higgins
3
Mercury spikes at the Cambrian Series 2 – 3 boundary: an imprint of the Kalkarindji LIP?
18
Luke Faggetter, Paul B. Wignall, Sara B. Pruss, David S. Jones, and Stephen E. Grasby
A non-toxic and inexpensive histological microtechnique for biological and paleobiological
research
19
Qin Leng and Hong Yang
A Phylogenetic Signal for a Paleoproterozoic Reorganization of the Global Sulfur Cycle 20
Greg Fournier, Cara Magnabosco, Kelsey Moore, and Joanna Wolfe
Abstracts for Poster Presentations
1– δ13C of the non-equilibrium marine carbon cycle after the Marinoan snowball earth
21
Frasier Liljestrand, David Johnston, and Francis Macdonald
2– A molecular geobiological approach to study the Miocene Clarkia lacustrine fossil
Lagerstätten
22
Hong Yang and Qin Leng
3– Do Mercury Enrichments in the Mesozoic Rift Basins of Eastern North America
Provide a Link Between Flood Basalt Volcanism and the End-Triassic Extinction?
23
Brian J. Beaty, David S. Jones, and Morgan F. Schaller
4– A mineralogical fingerprint for Burgess Shale-type fossilization
24
Ross P. Anderson, Nicholas J. Tosca, Nicolás Mongiardino Koch, and Derek E.G. Briggs
5– Phylogenetic Analysis of Cyanobacterial Carboxysome Proteins
25
Makayla Betts and Gregory Fournier
6– Mineral Interactions in Microbial Mats
26
Almariet Palm and Pieter Visscher
7– Abrupt terrestrial cooling at the Eocene-Oligocene transition: Implications for climate
and ecology
27
David Auerbach, Michael T. Hren and Astrid Pacini
8– A geochemical framework in retrieving the linked depositional and diagenetic histories
of marine carbonates
28
Mingyu Zhao
9– Interpreting ancient marine redox from carbonate iodine records
29
Dalton Hardisty, Sune Nielsen, Tristan Horner, and Scott Wankel
10– Iron Cycling in Two Sedimentary Regimes: The North Atlantic and
Japan Sea 30
Chloe Anderson and Richard W. Murray
4
11–A carbonate Li record through Earth's history
31
Boriana Kalderon-Asael, Noah J. Planavsky, and Dan Asael
12–A quantitative framework linking extinction magnitude, selectivity, and effect on biotic
composition
32
Andrew M. Bush, Steve C. Wang, and Jonathan L. Payne
13–Insights into the Biological Role Associated with Microbialite Formation at Pavilion
Lake, BC, Canada.
33
Kaliopi Bousses and Jennifer Biddle
14–What can carbonate diagenesis tell us about ancient seawater
chemistry?
34
Anne-Sofie C. Ahm, Christian J. Bjerrum, Clara L. Blättler, and John A. Higgins
15–Photogeochemical reactions under anoxic conditions
35
Winnie Liu, Nathan Yee, and Paul Falkowski
16–Refining Carbonate Leaching Methods for Radiogenic Sr Isotope Analysis
36
Eric J. Bellefroid and Noah J. Planavsky
17–Microfossils from the Cryogenian Period of the Rasthof Formation,
Namibia
37
Kimberly Du
18–A new estimate of detrital redox-sensitive metal concentrations and variability in
marine sediments
38
Devon Cole, Shuang Zhang, and Noah Planavsky
19–Microbial Communities in a Meromictic Lake
39
Kristin Yoshimura, Jennifer Biddle, and Svetoslava Todorova
20–Nutrient & translation limitation effects on sulfur isotope fractionation
40
Ying Lin, Boswell Wing, and Peter Douglas
21–Active microbial communities in Baltic Sea Basin sediments
41
Laura A. Zinke, Brandi Kiel Reese, Jordan Bird, Ian P.G. Marshall, Bo Barker Jorgensen,
Karen G. Lloyd, and Jan P. Amend
22–Investigating controls on boron isotope ratios in shallow marine carbonates
42
Shuang Zhang, Michael J. Henehan, Pincelli M. Hull, R. Pamela Reid, Dalton S. Hardisty,
Ashleigh v.S. Hood, and Noah J. Planavsky
23–The CO2-dependence of carbon isotope fractionation in a dinoflagellate employing
Form II RubisCO
43
Elise B. Wilkes, Susan J. Carter, and Ann Pearson
24–The Effect of the Cretaceous-Paleogene Extinction on Deep Sea Calcium Carbonate
Accumulation
44
Claudia Deeg, Brenna Getzin, and Sara Pruss
5
25–Unusual Seafloor Precipitated Carbonate Fans of the Neoproterozoic Rainstorm
Member
45
Chiza Mwinde, Kristin Bergman, Marjorie Cantine, Blair Schoene and Sara Pruss
26–Mercury chemostratigraphy leading into the Sturtian Snowball Earth glaciation: a
volcanic aerosol link between volcanism and global glaciation?
46
Christopher Hodge, David Jones and Francis Macdonald
27–Triple oxygen isotope systematics in the global sulfur cycle
47
Anna Waldeck and David Johnston
28–Microbial alteration of the hydrogen and carbon isotopic composition of n-alkanes in
sediments
48
Alex Brittingham, Michael Hren, and Gideon Hartman
29–Linking Laurentia’s Latitude to Neoproterozoic Diversification of Eukaryotes
49
Athena Eyster, Benjamin Weiss, Karl Karlstrom, and Francis Macdonald
30–Well-preserved marine carbonates record the oxygenation with the rise of land plants50
Ashleigh Hood, Malcolm W. Wallace, Alice Shuster, Christopher Reed and Noah Planavsky
31–Temperature records from Marinoan-age low latitude carbonates
51
Adam Jost and Kristin Bergmann
32–Reinterpretation of putative tintinnid lorica fossils from the Neoproterozoic Tsagaan
Olom Group, Mongolia
52
Maoli Vizcaíno, Phoebe Cohen and Ross P. Anderson
33–Two pulses of oceanic environmental disturbance during the Permian–Triassic
boundary crisis
53
Jun Shen and Noah Planavsky
34–Prospects for Bamboo Corals as Barium-based Archives of Bathypelagic Ocean
Circulatory Structure
54
Ben Geyman, Tristan Horner, Jamie Ptacek, Maureen Auro, Tessa Hill, and Michèle LaVigne
35–Understanding oxygen isotope trends during microbial sulfate reduction: A new
approach integrating pure culture experiments, statistical tools, and steady state isotope
models
55
Emma Bertran, Anna Waldeck, Boswell Wing, Itay Halevy, and David Johnston
36–Calcium isotopes in elasmobranch teeth as a window into modern and ancient marine
ecology
56
Alliya Akhtar and John Higgins
6
37–Constraining Mesoproterozoic oxygen levels through the multiple sulfur isotope
stratigraphy of the Bylot Supergroup, Baffin Island, Nunavut
57
Kelsey G. Lamothe, Peter W. Crockford, Marcus Kunzmann, Malcolm S.W. Hodgskiss,
Timothy Gibson, Sarah Worndle-Quoex, and Galen P. Halverson
38–Geochemical fingerprints of maximum flooding surfaces in the >811 Ma Fifteenmile
Group, Yukon reflect the iron shuttle
58
Timothy M. Gibson, Marcus Kunzmann, Galen P. Halverson, and André Poirier
39–Stratigraphy and paleoenvironments of the Kellwasser Events in the Upper Devonian of
the Southern Tier of New York and north-central Pennsylvania
59
J. Andrew Beard, Michael T. Hren, Andrew M. Bush
40–Microbial Analysis, Resources, and Services (MARS), UConn CORE
Kendra Maas
41–No safer in the south: The Cretaceous–Paleogene (K–Pg) mass extinction event and
recovery in Antarctica
James D. Witts, Rowan J. Whittle, Paul B. Wignall, J. Alistair Crame, Jane E. Francis,
Robert J. Newton, Vanessa C. Bowman
60
61
7
Lipid H-isotopic ratios from anaerobic bacteria record past energetic state
William D. Leavitt, Theodore M. Flynn, Sean J.L. Murphy, Melanie Suess, Lee Lynd,
and Alexander S. Bradley
A significant range in microbial lipid 2H/1H ratios is observed in modern marine sediments. The
magnitude of hydrogen isotope fractionation between microbial lipids and growth water (2εlipidH2O) is hypothesized to relate to the central carbon and energy metabolism. These observations
have raised the intriguing possibility for culture independent identification of the dominant
metabolic pathways operating in environments critical to the geological record. One such
metabolism we would like to track for its global significance in sedimentary carbon cycling is
bacterial sulfate reduction (BSR). To-date, BSR are known to produce lipids depleted in fatty
acid H-isotope composition, relative to growth water (2εlipid-H2O ~ -100 to -350 ‰), with
experiments on different substrates show large-scale variability, but no clear trend. Similarly,
aerobic heterotrophs show a wide range in fractionations (2εlipid-H2O ~ +300 to -125‰), though a
driving mechanism remains unclear. Recent work in aerobic methylotrophs implicates
transhydrogenase (TH) exerts a critical control on 2εlipid-H2O. This work suggests a specific
driving mechanism for this range in fractionation is the ratio of intracellular
[NADPH/NADH]:[NADP/NAD], and more fundamentally cellular redox state. In anaerobic
bacteria (BSRs, fermenters, others) a key component of energy metabolism is the activity of
electron-bifurcating THs, for which a mutant libraries exist in model organisms Desulfovibrio
alaskensis strain G20 (G20) and the thermophilic fermenter, Thermoanaerobacterium
saccharolyticum (Tsac). In this study we compare growth rates, fatty acid concentrations and
2
εlipid-H2O from wild type and TH mutants in strains of G20 and Tsac. We observed significant
growth rate and isotopic phenotypes when TH is involved in energy metabolism (changes in
2
εlipid-H2O of >150‰ in G20, >30‰ in Tsac). We discuss implications for understanding Hisotope fractionation between water and fatty acids preserved in anoxic sediments.
8
A glimpse at the lichen symbiosis; from metal homeostasis to ecosystems
function
Romain Darnajoux, Xinning Zhang, Darcy McRose, Jolanta Miadlikowska, François
Lutzoni, Anne M. L. Kreapiel and Jean-Philippe Bellenger
Symbioses are important component of the biosphere, with many implications in major element
cycles both in terrestrial and marine environment. Among those symbioses, lichens represent an
even peculiar association between several partners from as much as three different kingdoms: a
fungi, a alga and/or the a cyanobacteria. Cyanolichen particularly are pioneer species that
participated in the first stage of ecological succession, only requiring various micro-nutrients to
be able to accumulate both carbon and nitrogen from inorganic atmospheric sources. Thus those
micro-nutrients are of particular importance for the performance of the symbiosis, as well as for
the establishment of ecological succession. However most studies mainly use lichens as biomonitoring tools for metals in the environment, while only a few studies have concentrated on
characterizing the regulation of micro-nutrient between the different partners of the symbiosis.
Using the tri-membered cyanolichen Peltigera aphthosa as a model, we investigate the
homeostasis of important micro-nutrient inside each component of the symbiosis. Particularly,
we characterized the regulation of molybdenum (Mo) and vanadium (V), essential to biological
nitrogen fixation.
Our results show that the distribution of micro-nutrients between the different symbionts is in
accordance with their anticipated role inside the symbiosis. Particularly, the concentration of V
and Mo inside the cyanobacterial part of the thallus show a tight co-regulation, with V being
abundant when Mo is limiting, which is consistent with the available literature.
Those results have implications for our conception of the symbiosis as a whole and as the sum of
the parts. It also demonstrates the potential of studying the regulation of micro-nutrient inside the
symbiosis to get a better insight into crucial biogeochemical function.
9
How strange was the Strangelove Ocean?
Michael J. Henehan, Andy Ridgwell, Ellen Thomas, Shuang Zhang, Noah J.
Planavsky, Laia Alegret, Daniela N. Schmidt, James W. B. Rae, Gavin L. Foster, Brian
T. Huber and Pincelli M. Hull.
The idea of the ‘Strangelove Ocean’1 has captured the imagination of
palaeoceanographers (and the public) since it was posited to explain the collapse or reverse in
surface–deep ocean δ13C gradients after the Cretaceous-Palaeogene (K-Pg) boundary1. It
describes a post-extinction ocean where primary productivity was drastically reduced,
eliminating the surface-to-deep carbon isotope gradient produced by the biological pump.
Survival of benthic foraminifera across the K-Pg (suggesting a persistent supply of organic
matter to the deep) is difficult to reconcile with this ideae.g. 2. Geochemical proxies also suggest
that severe export productivity reductions were at most regional3. This mismatch between
patterns in δ13C and other indicators has thus been interpreted as a signal of changing vital
effects in post-extinction pelagic calcifiers, toward lighter δ13C e.g. 2.
However, it may be that vital effects in earliest Palaeocene foraminiferal survivors can
account for only part of the convergence in δ13C between surface and deep ocean.4 In addition,
analysis of carbonate preservation after the K-Pg boundary indicates large-scale carbonate
system/ocean pH shifts at this time5, which could have produced secular changes in carbon
isotope signals. Here we present new paired benthic and planktic boron isotope measurements
that allow us to examine surface to deep ocean pH gradients (which in today’s ocean are driven
largely by biological activity) across the K-Pg boundary interval and into the early Palaeocene.
We then couple these to GENIE earth system model simulations to untangle the carbon cycle
drivers, both physical and biological, that could have caused these changes in ocean pH
gradients. We discuss implications for our understanding of this important interval in Earth
history, with reference to the mechanisms of Earth system recovery following mass extinction.
References:
1. Hsü, K. J. & McKenzie, J. A., 1985. AGU Geophysical Monograph Series 32.
doi:10.1029/GM032p0487
2. Alegret, L., et al., 2012. PNAS 109, 728–732. doi:10.1073/pnas.1110601109
3. Hull, P.M. & Norris, R.D., 2011. Paleoceanography 26, PA3205. doi:10.1029/2010PA002082
4. Birch, H.S., et al., 2016. Geology 44, 287-290. doi:10.1130/G37581.1
5. Henehan et al., 2016. Phil. Trans. Roy. Soc. B. 371, 20150510. doi:10.1098/rstb.2015.0510
10
Deep life at the Tonga Trench: A metagenomic perspective from the surface
ocean to 2 meters below the sea floor
Rosa Leon Zayas, Douglas H. Bartlett, and Jennifer F. Biddle
Exploration of the deep ocean has expanded our understanding of oceanic ecosystems including
continental margins and mid-ocean ridges, but little is known about the deepest sites on Earth,
oceanic trenches. In this study, sediment and water samples were collected from the Tonga
Trench at 9100m below sea level. These include four water column samples at depths of 400m,
3000m, 5000m and ~9100m, and sediment samples at 0, 1, and 2 meter below the seafloor
(mbsf). DNA was extracted and sequencing was performed for the recovery of metagenomic data
for all samples. The analysis of the sediment samples from Tonga Trench has provided a new
perspective of life in the deep ocean. The data for microbial community composition and
metabolic profiles at the surface sediments, 0 mbsf, suggest that the microbes are present and
taxonomically similar to the water column microbes, and perform an array of aerobic as well as
anaerobic metabolisms, including degradation of organic carbon, oxidative phosphorylation,
fermentation, nitrate reduction and sulfur oxidation among others. On the other hand, at 1 and 2
mbsf, the microbial community has diminished richness and diversity when compared to 0 mbsf
and is potentially environmentally degraded due to the lack of quality data recoverable. The
analysis of the water column samples has provided insights the adaptation of organism to
extreme deep trench environments. To our knowledge, this is the deepest metagenome analyzed
to date (9100m), presenting an unprecedented look at one of the deepest environments on our
planet.
11
Metal Availability and the Evolution of Archean Metabolisms
Eli Moore, Benjamin I. Jelen, Donato Giovannelli, Hagai Raanan, and Paul G.
Falkowski
Oxidoreductases are molecular nanomachines responsible for all biologically driven electron
transfer processes across the tree of life. These enzymes often contain transition metals in their
active sites; the metals are critical for catalytic function. The availability of different metals and
substrates has changed over the course of Earth’s history as a result of secular changes in redox
conditions, especially because of global oxygenation. These secular changes led to a coevolution
of novel metabolisms that recruited different transition metals over geologic time. Here we
examine the geologic record for preserved biosignatures of redox changes in the Archean oceans
with the goal of dating the approximate time of origin of specific metabolic pathways and their
redox metal utilization. Assuming the centrality of hydrogen metabolism as an initial condition,
we trace biosignatures for sulfur reduction, sulfate reduction, methanogenesis and anoxygenic
photosynthesis at approximately 3.8 to 3.4 Ga. The oxidoreductases responsible for these
metabolisms incorporated readily available metals, primarily as iron sulfur clusters and hemes, in
the Archean ocean. Reliable biosignatures of nitrogen fixation, oxygenic photosynthesis,
methane oxidation and nitrification/denitrification appear between 3.2 to 2.5 Ga, accompanied by
an expanded usage of transition metals. In particular, the appropriation of copper immediately
preceding the Great Oxidation Event (GOE), allowed access to higher redox potentials and
substrate specificity. The distribution of oxidoreductase metal ligands shifted between microbial
taxa through time, indicating that surface redox potential and metal incorporation influenced the
evolution of metabolism, biological electron transfer and microbial ecology.
12
Environmental Adaptation from the Origin of Life to the Last Universal
Common Ancestor
Marjorie Cantine and Gregory P. Fournier
Between the origin of life and the Last Universal Common Ancestor (LUCA), life likely
diversified into environments unlike the one in which it emerged. Extensive fundamental
molecular and biological evolution took place, including the emergence of polypeptide-based
proteins, cellularity, DNA, and LUCA’s genome of up to 600 genes. Environmental temperature
and UV were likely key constraints on early prebiotic synthesis and life. Our assessment of
available experimental and phylogenetic evidence indicates a cold, shielded environment for
life’s origin, and a mesophilic, surface-dwelling LUCA.
We discuss evolutionary innovations between these two points as evidence for and drivers of
adaptive radiation pre-LUCA. We consider these evolutionary innovations from the perspective
of environmental adaptation, exploring the possibility that LUCA was both temporally and
environmentally removed from life’s earliest origins in the RNA world. This early environmental
adaptation indicates the important role that cellular motility and cellularity played in early
evolution, consistent with a pre-LUCA emergence of cellularity and compartmentation. Finally,
we discuss the promise and potential of considering environmental adaptation in life’s earliest
evolution.
13
A role for the alternative V-nitrogenase in redox homeostasis
Katja Luxem, Carol C. Chui, Anne M.L. Kraepiel, and Xinning Zhang
All biological nitrogen fixation is catalyzed by one of three isoforms of the metalloenzyme
nitrogenase. The canonical Mo-nitrogenase is considered the most efficient isoform and the key
enzyme responsible for nitrogen fixation in the environment. The ‘alternative’ V- and Fe-only
nitrogenases have been assigned the roles of ‘backup enzymes’ for N anabolism, useful when
Mo is limiting or at cold temperatures. However, genes for the alternative nitrogenases are
present in diverse taxa and environments, including Mo-replete, temperate ecosystems,
suggesting that these isoforms have additional physiological roles. We hypothesized that the
greater H2 production (and correspondingly larger reductant requirements) of the alternative
nitrogenases could be beneficial for organisms when balancing electrons is a dominant
physiological challenge. To test this hypothesis, we grew the anoxygenic diazotroph
Rhodopseudomonas palustris and modulated its redox stress by providing carbon sources with
different redox states for photoheterotrophic growth. When provided with the relatively oxidized
substrate succinate, diazotrophic growth based on V-nitrogenase was slower than that based on
Mo-nitrogenase. In contrast, use of the V-nitrogenase instead of Mo-nitrogenase for growth on
the more reduced carbon substrate acetate led to significantly faster growth (~30%). The
relationship between redox stress and nitrogenase usage is further supported by systematic
differences in [NADH]/[NAD+] and biomass C:N. Together, the data indicate that V-nitrogenase
can be used as an electron sink, which is a new physiological role for alternative nitrogenases
that can help explain their distribution in nature. Our results suggest that, in addition to cold or
Mo-limited environments, alternative isoforms like V-nitrogenase are likely to be active and
beneficial for growth in reducing environments as well, and invite a reconsideration of the role of
alternative nitrogenases in nitrogen cycling.
14
Revealing the genes responsible for sulfur respiration in Thermovibrio
ammonificans
Benjamin Jelen, Donato Giovannelli, and Costantino Vetriani
Thermovibrio ammonificans, in the deep-branching family Desulfurobacteriaceae (phylum
Aquificae), is a deep sea vent chemolithoautotrophic thermophile able to conserve energy from
the oxidation of hydrogen and respiration of both nitrate and elemental sulfur. Comparison of
growth under these two different electron-acceptor regimes was undertaken to elucidate the T.
ammonificans pathway of sulfur respiration - as well as to gain insight into its core (original, and
vertically acquired) versus its acquired (horizontally acquired) genes. A membrane and
cytoplasmic hydrogenase, as well as two FAD-dependent pyridine nucleotide disulfide
reductases (homologs to sulfide-quinone reductase (SQR) and to NADH-dependent sulfur
reductase (NSR)), were highly over-expressed during sulfur respiration.
Energy metabolism has co-evolved over billions of years alongside Earth’s geology, from a
purely anaerobic context to today’s metabolic diversity. This diversity has been realized by an
evolving network of electron-transfer enzymes. Sulfur, unlike oxygen or nitrate, would have
been an electron acceptor available to life during the earliest steps of metabolic evolution.
Enzymes dealing with its redox chemistry may be among the earliest relics of the oxidoreductase
family. The core “sulfur-reducing” proteome of the deep-branching family
Desulfurobacteriaceae (phylum Aquificae) can help better understand the early co-evolution of
energy metabolism and geochemistry.
15
Potassium isotopic composition of marine and freshwater fish: An example of
diffusive K fractionation in biological systems
Danielle Santiago Ramos and John A. Higgins
Potassium is an essential cation involved in ionic regulation, a vital feature of aquatic animals.
Fish have evolved different strategies to balance the ionic concentrations of their body fluids
against surrounding environments. Here, we measured the K concentration and isotopic
composition (41K/39K) of muscle tissue from marine and freshwater fish in order to understand
the mechanisms responsible for setting their K isotopic ratios. Measured δ41K values in muscle
tissue range from -0.72‰ to 0.44‰. Tissues from species that tolerate marine to brackish
salinities show average δ41K value (-0.39 ±0.40‰, 2
N=11) that is significantly lighter than
seawater (0‰). In contrast, the single freshwater sample analyzed is isotopically heavier (δ41K =
0.44‰) than all rivers measured in our lab (-0.38 ±0.26‰, 2 , N=13). Individuals from the
Salmonidae family, which are found across different salinities, have intermediate δ41K values
averaging 0.13 ±0.40‰. Our data are consistent with fish K isotopic ratios being controlled by
the ionic imbalance between fish body fluids and their surrounding environment. Specifically,
marine fish (which tend to passively gain K from seawater) are isotopically light, whereas our
single freshwater fish (which loses K to its surrounding via diffusion) is much heavier than any
measured river. Migratory individuals have intermediate δ41K compositions, as they experience
variable ionic pressures during their life cycle. Results from 1D model simulations of ionic
exchange in fish agree with our hypothesis that the observed variability in isotopic composition
can be explained in terms of K diffusion and active K pumping. The role of diffusive K
fractionation is further corroborated by experiment, whereby rinsing of the tissue samples prior
to acid digestion lead to measurable K loss and concomitant increase in the δ41K of remaining K.
To our knowledge, this is the first time that K isotopic fractionation is observed in biological
systems.
16
An independent constraint on marine sulfate levels at the Ediacaran–
Cambrian transition
Clara Blättler, Kristin Bergmann, John Higgins
Sediments from the Ediacaran–Cambrian transition in Oman record major excursions in the
isotopic systems of carbon (δ13C) and sulfur (δ34S). The significance of these geochemical
signals has been the subject of much debate, focusing on their association with biotic innovations
and extinctions, oxygenation of the atmosphere and oceans, and changes in seawater chemistry.
The concentration of marine sulfate during this time interval remains particularly uncertain,
despite being a critical variable for several hypotheses related to these excursions.
We present an independent constraint on relative sulfate concentrations based on calcium-isotope
data from the Ara Group evaporites (547–540 Ma) of the South Oman Salt Basin. Anhydrite
samples from five boreholes span the A1 through A5 carbonate-evaporite sequences, lying on
both sides of the Precambrian–Cambrian boundary. The approach developed by Blättler and
Higgins (2014) is used to quantify the isotopic distillation of calcium by sulfate mineral
precipitation. The absence of significant distillation (expressed by δ44/40Ca variability in the
anhydrite) suggests that Ca/SO4 ratios in the latest Ediacaran and earliest Cambrian were greater
than during the Neogene or Permian. These results, together with previously published analyses
of halite fluid inclusions and models of sulfur cycling, give a clearer estimate of how marine
sulfate levels may have evolved during this dynamic period in Earth history.
17
Mercury spikes at the Cambrian Series 2 – 3 boundary: an imprint of the
Kalkarindji LIP?
Luke Faggetter, Paul B. Wignall, Sara B. Pruss, David S. Jones, and Stephen E.
Grasby
The Cambrian Series 2- 3 boundary marks the first mass extinction of the Phanerozoic and, like
many other extinction intervals, coincides with a negative inorganic carbon isotope excursion
(ROECE) and the eruption of a large igneous province (Kalkarindji LIP). In the western Great
Basin (USA) the extinction of the olenellid trilobites lies within a succession of silty marls in the
Pyramid Shale Member of the Carrara Formation, at Emigrant Pass, Death Valley, California and
in the basal C-Shale Member of the Pioche Formation, Oak Springs Summit, eastern Nevada. At
both localities, we report a series of Mercury (Hg) spikes in the run up to, and within, the
extinction interval. In the Pioche Formation, background Hg concentrations are <5 ppb and
spikes range between 15-52 ppb. In the Carrara Formation background levels are again <5 ppb
with spikes between 100-270 ppb. In the Pioche Formation the extinction horizon is well
constrained and correlates directly with a Hg spike. Current dating of the Kalkarindji LIP yields
a zircon age of 510.7 +/- 0.6 Ma which is indistinguishable (within uncertainty) from the age of
the Cambrian Series 2- 3 boundary. Here we propose that the occurrence of elevated Hg spikes
are of volcanic origin, are derived from the Kalkarindji LIP, and may have caused the extinction
of the olenellids.
18
A non-toxic and inexpensive histological microtechnique for biological and
paleobiological research
Qin Leng and Hong Yang
Histological microtechniques have a long history to be widely used in many research fields in
biology and geobiology. However, traditional methods heavily involve large amounts of organic
solvents such as ethanol, methanol, acetone, xylene, toluene, benzene, and/or chloroform, many
of which are not only toxic, being serious health hazards, but also expensive, limiting the
availabilities of this effective technology in university laboratories with limited space, facilities,
and/or budget. We developed a non-toxic and inexpensive alternative method to prepare
histological thin sections of both modern and fossil materials to observe their anatomical
structures under microscopes. In this method, isopropanol (IPA), a safe and economic
commercial chemical, is used to replace toxic organic solvents in the steps of tissue processing
(dehydration/dehydrating, clearing/defatting, infiltration/infiltrating, and
impregnation/impregnating), embedding ("blocking" or "blocking out"), staining, and coverslip
mounting ("coverslipping") by carefully adjusting the temperatures and timing of their usage in
the procedures. By using this method, our laboratory has successfully prepared histological slides
of Paleogene and Neogene plant leaf fossils, archeological plant materials, and living plant
tissues for projects of terrestrial environment research. We believe that this method is an efficient
and affordable alternative to the traditional histological microtechniques for biology and
geobiology research.
19
A Phylogenetic Signal for a Paleoproterozoic Reorganization of the Global
Sulfur Cycle
Greg Fournier, Cara Magnabosco, Kelsey Moore, and Joanna Wolfe
The sulfur cycle is one of the most significant biogeochemical cycles on Earth today, mapping
the flux of sulfur through mineral, marine, and biological systems. Several distinct microbial
metabolisms mediate redox state changes in sulfur. Of particular importance are dissimilatory
sulfate and sulfur reduction energy metabolisms, and the oxidation of sulfide as part of microbial
anoxygenic photosynthesis. The former are primarily performed by members of
Deltaproteobacteria and Firmicutes, while the latter are primarily performed by green and purple
sulfur bacteria. While isotopic data has been interpreted as showing a very old origin of
biological sulfate reduction before 3.47 Ga, there is also geological evidence for very low levels
of sulfate before the Great Oxygenation Event (GOE) ~2.3 Ga. We perform phylogenetic and
calibrated molecular clock analyses of these microbial clades. We show a consistent pattern of
sulfate reducing bacteria and sulfide-utilizing phototrophic bacteria diversifying during the
Paleoproterozoic, shortly after the GOE. Purple sulfur bacteria appear to have rapidly diverged
and diversified during this time, while green sulfur bacteria may have had an earlier origin, due
to a longer stem lineage. Interestingly, Deltaproteobacteria phylogeny shows the most basal
groups performing elemental sulfur reduction, with more derived groups transitioning to
exclusive sulfate reducing metabolisms during this time interval. This transition may track with
the shifting redox state of sulfur within sediments, capturing the interval of the GOE itself. Highresolution “lineage through time” metrics may also provide key indicators of diversification rates
of sulfate-reducing species, a proxy for ecological expansion sulfate availability. In this way,
phylogenetic studies can provide independent evidence of major geochemical transitions in
Earth’s history, to both validate and complement interpretations of the geological record.
20
δ13C of the non-equilibrium marine carbon cycle after the Marinoan snowball
earth
Frasier Liljestrand, David Johnston, and Francis Macdonald
Throughout most of the sedimentary record, the marine carbon cycle can be described as a steady
state isotope system. Two export fluxes, organic carbon and carbonate, are offset by a constant
δ13C fractionation of about 25‰, and shifts in the combined isotopic value reflect the relative
burial fraction of each flux. However, particularly in times when the marine carbon cycle is not
at steady state, this pattern may not be observed. The deposits formed immediately after the
Marinoan snowball earth event in the Neoproterozoic reflect one such time. In carbonates from
the Ol formation in Mongolia and the Sheepbed formation in Canada we observe a transient nonequilibrium isotopic offset between carbonate and organic carbon of about 10‰. In order to
explain this observation, we developed a model that simulates the Ocean-Atmosphere system
immediately after the termination of snowball Earth, continuing through the end of the stratified
ocean. This three box model tracks the fluxes of carbon between the surface ocean, deep ocean,
and atmosphere, and calculates the resulting sedimentary isotope signal. Based on the model, we
conclude that no reasonable combination of normal marine processes can reproduce the observed
trend in organic carbon δ13C. The regional isotope signal is most likely explained by the
temporary and diminishing input of a separate source of heavy organic carbon, possibly from the
continents.
21
A molecular geobiological approach to study the Miocene Clarkia lacustrine
fossil Lagerstätten
Hong Yang and Qin Leng
The world-renowned Middle Miocene Clarkia lacustrine Lagerstätten (15.4–16.0 Ma) in northern
Idaho, USA yield extraordinary fossils that preserve in situ ancient biomolecules and organic
biomarkers. The past three decades have witnessed many cutting edge technologies initially
applied to Clarkia materials to demonstrate the feasibility of these novel methods in geobiology.
New developments of quantitative organic geobiochemical proxies have made it possible to
independently test previous paleoenvironmental reconstructions based upon traditional
paleontological and sedimentological evidence for conditions both within the lake basin and its
surroundings. We summarize these results from recent quantitative analyses, including: (1) a
review of biomolecules recovered from Clarkia fossils and sediments, (2) molecular and
micromorphological analyses of the extraordinary preservation of Clarkia plant fossils, (3)
paleohydrological dynamics based upon molecular hydrogen isotope analysis of in situ lipids,
and (4) a rapid lake shallowing event, based upon new glycerol dialkyl glycerol tetraether
(GDGT) analysis of sequential samples along the type P-33 location section, switching lacustrine
conditions from a conservation deposit (Konservat-Lagerstätte) to a concentration deposit
(Konzentrat-Lagerstätte). Quantitative geobiological analyses not only provide new insights into
the extraordinary preservation of Clarkia megafossils and biomolecules but also offer valuable
data for better understanding of global climatic and atmospheric conditions of the critical global
warming period during Middle Miocene Climatic Optimum.
22
Do Mercury Enrichments in the Mesozoic Rift Basins of Eastern North
America Provide a Link Between Flood Basalt Volcanism and the EndTriassic Extinction?
Brian J. Beaty, David S. Jones, and Morgan F. Schaller
A strong temporal correlation between Large Igneous Provinces (LIPs) and mass extinctions
exists throughout the Phanerozoic. However, in the Triassic-Jurassic continental rift basins of
eastern North America, the End-Triassic extinction (ETE) underlies the oldest local expression
of the Central Atlantic Magmatic Province (CAMP), complicating the presumed causal
relationship between LIP volcanism and extinctions. Here we test the hypothesis that the ETE
was driven by a recently-reported earlier initiation of CAMP volcanism in western African
basins using mercury (Hg) chemostratigraphy. Hg is an emerging proxy for LIP volcanism in
sedimentary successions given its primarily volcanic origin and demonstrated potential for global
dispersal after historic eruptions. Following the recent discovery of Hg enrichments in marine
strata spanning the ETE in Muller Canyon, Nevada, here we report Hg enrichments in fluvial and
lacustrine strata of the Newark, Hartford, and Deerfield basins in eastern North America.
Enrichments in both Hg and Hg/TOC are ~15x higher than background values within the first 10
m of sediments overlying the Deerfield Basalt, the earliest local expression of CAMP in the
Deerfield Basin; similar-magnitude enrichments occur within organic-rich lake deposits. We
interpret the enrichments above the Deerfield Basalt as evidence of an increase in atmospheric
Hg from volcanic outgassing; the origin of lake deposit enrichments is tentatively attributed to
enhanced Hg scavenging by aquatic vs. terrestrial biomass. Ongoing measurements of Hg across
the extinction interval in the Newark and Hartford basins will determine if a precursor signal for
CAMP volcanism exists in eastern North America. Although these results demonstrate that a
better understanding of Hg cycling and preservation is needed to distinguish global volcanogenic
signals from the effects of facies changes, this is the first evidence of a LIP-associated Hg
enrichment in a continental setting for ETE.
23
A mineralogical fingerprint for Burgess Shale-type fossilization
Ross P. Anderson, Nicholas J. Tosca, Nicolás Mongiardino Koch, and Derek E.G.
Briggs
Burgess Shale-type (BST) fossils that preserve carbonaceous remains, which ordinarily decay
away, are a vital source of paleobiological information. Their utility has been demonstrated most
strikingly in investigations of the Cambrian explosion of animal diversity, but they are also the
major repository for Proterozoic eukaryotic fossils. The fossils are carbonaceous remains
compressed parallel to bedding in fine-grained siliciclastic rocks. Sediment composition of BST
localities, and the abundance of certain clay minerals in particular, has been invoked as a
significant factor in their taphonomy. Clays have been posited to slow decay via adsorption and
deactivation of autolytic enzymes, their involvement in the polymerization of organic tissues,
and their toxicity to bacterial growth. However, geological evidence for associations between the
abundance and mineralogy of clays, and occurrences of BST fossils, is scant.
Here we test the association of clay mineral assemblages with BST fossil-yielding rocks. XRD
data for 213 Cambrian shales from 19 sedimentary successions on four continents (131 with
carbonaceous remains and 82 without) suggest that BST rocks have restricted clay compositions.
Multiple logistic regression reveals that increased abundances of berthierine and kaolinite, and
decreased abundances of Fe-rich illite and illite significantly increase the probability of
carbonaceous preservation. A data mining approach creates rules to identify rocks likely to
preserve BST fossils with an accuracy of 80.3%. The conditions Fe-rich illite ≤ 1.68%, illite ≤
23.59%, and berthierine > 0% almost always yield rocks with BST fossils (probability = 0.978).
These results demonstrate for the first time a geological association between specific mineral
abundances and BST fossilization. They provide a mineralogical fingerprint that can be used to
refine the search image for BST fossils on Earth and beyond.
24
Phylogenetic Analysis of Cyanobacterial Carboxysome Proteins
Makayla Betts and Gregory Fournier
Carboxysomes are polyhedral microcompartments that concentrate carbon dioxide around
ribulose 1,5-bisphosphate carboxylase (RuBisCO) to increase the efficiency of oxygenic
photosynthesis. Despite their abundance in cyanobacteria, the organisms responsible for
oxygenating Earth’s atmosphere, carboxysomes have a much more broad distribution among
microbial groups and their evolutionary origin is unclear. Understanding the history and
physiological limits of carboxysomes could yield important information about the evolution of
Earth’s atmosphere, especially regarding changes in the relative and absolute levels of oxygen
and carbon dioxide. There are two types of carboxysomes, α and β, which correspond,
respectively, to the 1A and 1B form of RuBisCO they house, and their associations within the
cyanobacterial tree appear to be distinct. α cyanobacteria are found largely in open marine
environments and include the globally abundant Synechococcus and Prochlorococcus, while β
cyanobacteria are found in a more diverse range of environments. Previous studies have
suggested that genes encoding cyanobacterial α carboxysome structural proteins were
horizontally transferred from within Proteobacteria (Abdul-Rahman et al., J. Phylogen Evolution
Biol, 1:118 (2013); Cai et al., Life, 5:1141-1171 (2015); Whitehead et al., Plant Physiology,
165:398-411 (2014)). Here, we perform a more comprehensive phylogenetic analysis of these
protein families in order to better support and constrain carboxysome history. A well-resolved
phylogeny of carboxysome-associated proteins permits time-calibrated molecular clock analyses,
detection of horizontal gene transfers, and reconstruction of ancestral protein sequences, all of
which permit the elucidation of carboxysome origins. These results can provide key insights into
the early evolution of earth’s atmosphere, and the biological response to it, in the context of
carbon fixation and primary production.
25
Mineral Interactions in Microbial Mats
Almariet Palm and Pieter Visscher
Diatoms are ubiquitous at the surface of microbial mats but their frustules are not observed at
depth, a puzzling phenomenon that is not well understood. The question remains whether
diatoms are absent within fossil mats because they were not present, or because they were not
preserved. The disappearance of frustules may be due to their dissolution, which increases with
elevated pH. Microbial metabolic reactions within the mat, such as intense photosynthesis by
cyanobacteria and certain types of anaerobic heterotrophic metabolisms, create alkaline
conditions. The resulting increase in pH facilitates dissolution of biogenic silica. We explored
the dissolution of diatom frustules in three experiments 1) abiotically at elevated pH in a
buffered solution 2) biologically with cyanobacterial cultures seeded with diatom frustules and 3)
in natural mats. The pH and dissolved silica were monitored. Light microscopy and SEM will be
used to investigate evidence of pitting and etching of the frustules. Increased understanding of
the fate of diatoms in extant systems can be used as a proxy for paleoreconstruction of extinct
mats, diagenesis and preservation mechanisms.
26
Abrupt terrestrial cooling at the Eocene-Oligocene transition: Implications
for climate and ecology
David Auerbach, Michael T. Hren and Astrid Pacini
Earth’s climate transitioned from the greenhouse conditions of the Eocene to the icehouse of the
Oligocene ~34 million years ago. Global cooling resulted from a decrease in atmospheric CO2
and is associated with the first appearance of large, permanent ice-sheets on Antarctica. The
Eocene-Oligocene transition (EOT) is marked by a large increase in the δ18O of benthic
foraminifera, reflecting a combination of cooler global temperatures and continental ice growth.
We measured hydrogen isotopes of volcanic glasses deposited in Patagonia during the EOT to
reconstruct temperature change during this critical climate transition. These data show
Patagonian terrestrial mean annual temperature (MAT) decreased by ~6°C during the EOT but
returned to pre-EOT values by the early Oligocene, indicating close coupling of temperature and
atmospheric CO2. Our results also suggest the EOT is marked by a rapid cooling “event” in the
terrestrial realm, prior to long-term cooling during the early Oligocene. This magnitude of
cooling, as well as the pattern of rapid temperature change followed by a more gradual recovery
matches well with nearby marine records. The rapid terrestrial climate fluctuations during the
EOT may be associated with suppression of wildfire (Selkin et al., 2015) and possible increases
in canopy openness (Dunn et al., 2015); however, the composition of floral communities
populations (Strömberg et al., 2013) and evolution of grazing mammals (Kohn et al., 2015) show
little response. This broadly emphasizes that the cooling associated with the EOT was expressed
globally in the terrestrial realm as well as the marine realm, but the local effects of that cooling
varied considerably, particularly for regional ecosystems.
27
A geochemical framework in retrieving the linked depositional and diagenetic
histories of marine carbonates
Mingyu Zhao
In modern shallow-water carbonate platforms, successive changes of diagenetic zones were
found as a result of a drop in sea level. Such a relationship is important in the identification of
diagenetic processes, in the interpretation of global carbon isotope shifts and in finding the
reasons for positive correlations between carbonate carbon and oxygen isotopes. However, it is
not readily recognized in ancient carbonates because evidences for sea level changes can be
cryptic in rock record. To solve this issue, we carry out a combined study of rare earth elements
and yttrium (REE+Y) and C-O isotopes of Carboniferous-Triassic marine carbonates from the
Lower Yangtze region in China. The relationships between inter-REE+Y ratios such as Y/Ho vs.
(Nd/Yb)PAAS for pure carbonates strongly indicate mixing between fresh water and surface
seawater. The REE+Y patterns for pure carbonates show regular temporal variations, reflecting
regular changes in the proportion of fresh water addition to surface seawater, which were likely
due to changes in relative sea level. Changes in diagenetic zones indicated by the relationships
between carbonate C-O isotopes and other variables follow the changes in relative sea level
suggested by the REE+Y patterns. Therefore, a combined study of the REE+Y and C-O isotopes
in pure carbonates can provide robust constraints on the changes in the linked depositional
environments and diagenetic processes of marine carbonates.
28
Interpreting ancient marine redox from carbonate iodine records
Dalton Hardisty, Sune Nielsen, Tristan Horner, and Scott Wankel
Iodine abundances in foraminifera and laboratory-precipitated calcite have been demonstrated to
record the availability of the oxidized iodine species, iodate, in seawater. This approach has
unique value as a paleoredox tracer, as marine iodate is exclusive to oxic settings, iodine
speciation shifts dramatically in modern oxygen minimum zones, and, accordingly, carbonate
iodine contents vary across geologic intervals characterized by shifts in marine oxygen
concentrations (e.g., OAEs, GOE). However, interpretations and quantitative applications are
currently limited, as carbonate iodine contents are under characterized in modern settings,
diagenetic effects on proxy values are completely unknown, and the mechanisms and rates of
dissolved iodine redox reactions in seawater have been elusive for decades. Here, we provide a
comprehensive interpretative framework for ancient carbonate iodine contents through a study
tracing iodine redox reactions in seawater and during carbonate diagenesis. Iodine behavior
during carbonate diagenesis is constrained through a comparison of iodine contents in diagenetic
low-Mg calcite and dolomite to that of primary aragonite and high and low-Mg calcite from the
the Bahamas. We demonstrate that iodine contents most often decrease, but do not increase,
during diagenetic mineral transformations. With this context, we provide multiple examples of
how modern carbonate geochemistry can inform interpretations of surface ocean oxygen levels
from Precambrian carbonate iodine records. In addition, we outline preliminary results for a new
tracer method designed to quantify rates and mechanisms of iodine redox reactions in seawater
through introduction of a radiogenic iodine isotope (I-129) into seawater incubation experiments.
We specifically determine 129/127I in each the oxidized and reduced iodine species through
chromatographic separation and quantification via multicollector-inductively coupled plasma
mass spectrometry.
29
Iron Cycling in Two Sedimentary Regimes: The North Atlantic and Japan Sea
Chloe Anderson and Richard W. Murray
Iron (Fe) in marine sediments is a significant microbial electron acceptor [Fe(III)] in suboxic
conditions and is an electron donor [Fe(II)] in oxic conditions. In the transition from oxic to
suboxic sediment, a portion of solid Fe is reduced and mobilized as soluble Fe(II) into interstitial
water during the oxidation of organic matter. The presence of Fe and its oxidation state in oxic
sediment provides insight into an important metabolic and mineral reaction pathway in
subseafloor sediment.
We selected a collection of bulk sediment and interstitial water samples to target Fe cycling in a
variety of marine environments. A series of sites were drilled during International Ocean Drilling
Expedition 346 in 2013, and here we present samples from sites U1429 (East China Sea) and
U1430 (Japan Sea). We also present samples from oxic (Site 12) and suboxic (Site 10) sediment
regimes collected during R/V Knorr Expedition 223 in the western North Atlantic in 2014.
We present total solid Fe concentration from 145 bulk sediment samples and total aqueous Fe
and Mn from 160 interstitial water samples analyzed via ICP-emission spectrometry. We
additionally present Fe(II) and Fe(III) speciation results from 17 solid sediment samples
determined by Mossbauer spectroscopy. We trace downhole fluctuations of Fe in solid and
aqueous phases to understand Fe cycling in oxic, suboxic and transitional regimes in multiple
marine settings, including environments with increased discrete and dispersed volcanic ash.
30
A carbonate Li record through Earth's history
Boriana Kalderon-Asael, Noah J. Planavsky, and Dan Asael
Lithium (Li) isotopes emerge as a powerful geochemical proxy for tracking continental
weathering through time. Extensive work on Li fractionation in modern systems has brought to a
profound understanding of the modern Li budget as well as to a consensus that marine
carbonates faithfully record seawater Li isotope signature. As such record is essential in order to
track global-scale changes in weathering processes and intensity through Earth’s history, we
have generated Li isotope data from marine carbonates from over 40 units, ranging in age from
3.0 Ga to modern. Preliminary results provide evidence for strongly inhibited weatheringmediated clay formation prior to the Paleozoic, which we attribute to the pre-Paleozoic lack of
land plants. The initial rise in the Li isotope values is observed during the Ordovician, which is
followed by a subsequent drop to background values and then begins the generally increasing
trend that is already well reported. These findings are open for interpretation but they still
support the view that the emergence of land plants dramatically changed the process of
weathering and it seems that biomass has a potentially significant role in mineral breakdown in
soils. Li isotopes provide a novel perspective on weathering and the impact on the Earth system
of the rise of land plants – one of the most significant transitions in Earth’s history.
31
A quantitative framework linking extinction magnitude, selectivity, and effect
on biotic composition
Andrew M. Bush, Steve C. Wang, and Jonathan L. Payne
Mass extinctions are often ranked based on magnitude (e.g., the proportion of species or genera
that go extinct). However, the effects of an extinction event on the composition of a biota depend
on both magnitude and selectivity—that is, both the intensity of the event and the variation in
intensity among groups or with respect to some trait. An increase in either selectivity or
magnitude will result in a greater change to the composition of the biota, which implies greater
macroevolutionary importance. Here, we describe a quantitative framework for separating the
contributions of magnitude and selectivity in driving change in biotic composition, where
composition is construed as the relative richness of different clades or functional groups. If
q1...qn are defined as the values for extinction magnitude for n groups using the boundary-crosser
metric, then overall extinction magnitude (M) is defined as the average of q1...qn. We show that a
simple measure of compositional change (C) based on logged values is equal to the standard
deviation of q1...qn, and we define selectivity as the coefficient of variation of q1...qn, which
equals C/M. Thus, the amount of change in biotic composition equals the product of magnitude
and selectivity (C = SM). Due to the multiplicative relationship between selectivity and
magnitude, compositional change will be extremely high when high values of S and M coincide.
We apply this new framework to the Phanerozoic record of extinction in marine animals. The
end-Permian extinction and Early Triassic recovery interval stand out as unusually selective, at
least for higher magnitude events. The unique macroevolutionary importance of the PermianTriassic transition derives from the unique coincidence of high magnitude and selectivity.
32
Insights into the Biological Role Associated with Microbialite Formation at
Pavilion Lake, BC, Canada.
Kaliopi Bousses and Jennifer Biddle
Microbialites form as a result of the trapping of sedimentary grains from microbial mats.
Although these biochemical structures have been present since Earth’s early life history, their
existence in modern times is fairly rare. Located in Marble Canyon, British Columbia, Pavilion
Lake is home to the largest freshwater microbialite bed in the world. This study used amplicon
sequencing in order to discover the underlying differences in microbial communities between the
micro-stromatolitic nodules that appear on microbialites, as well as any community shifts that
occur along the vertical length of these structures. Specifically, pink and green nodules showed
differences in several groups of cyanobacteria. Moreover, along the length of a microbialite
mound, the phyla that prevailed were Proteobacteria, Cyanobacteria and Chloroflexi.
33
What can carbonate diagenesis tell us about ancient seawater chemistry?
Anne-Sofie C. Ahm, Christian J. Bjerrum, Clara L. Blättler, and John A. Higgins
Most of our understanding of the global carbon cycle and climatic history of Earth is based on
the record of carbon isotope variation (13C) in ancient carbonate rocks. Inexplicable negative 13C
excursions below the canonical mantle value, however, are found in carbonate rocks of
Precambrian age (>542 Ma). One of the main concerns are that these enigmatic 13C anomalies
may be artifacts of secondary diagenetic alterations and not records of global seawater chemistry
and carbon cycling. Diagenesis can occur both early (syn-depositional) and late (postdepositional), involving both meteoric and marine fluids, and is prevalent in ancient carbonate
rocks. To provide quantitative information on the extent of diagenetic alteration, we develop a
numerical model of marine carbonate diagenesis. The model tracks the elemental and isotopic
composition of Ca, Mg, C, O, and Sr during dissolution of primary carbonates and reprecipitation of secondary minerals. The model is ground-truthed by measurements of these
isotopic systems from sites on the bank top and slope of the Bahamas platform that are
associated with large and systematic changes in carbonate mineralogy, isotopic compositions,
and elemental geochemistry with depth. The model predicts that the observed geochemical
signatures originate from pervasive marine diagenesis, where recrystallization, neomorphism,
and dolomitization occur in either seawater-buffered or rock-buffered pore waters. By modeling
the isotopic trajectories between these diagenetic end-members, we can estimate the original
composition of the concurrent infiltrating seawater. Carbonate rocks that have been recrystallized
during extensive seawater-buffered marine may provide a previously unexplored archive of
ancient seawater chemistry ranging from Precambrian Snowball Earth events to the Pleistocene.
34
Photogeochemical reactions under anoxic conditions
Winnie Liu, Nathan Yee, and Paul Falkowski
Photogeochemistry, photochemical reactions with natural components, has influenced the
biogeochemistry of Earth. In particular, reactions caused by high energy UV radiation during
early Earth could have influenced the development of life by changing environmental conditions
or through the production of biologically important compounds. This period of time is
characterized by the lack of oxygen and enhanced UV radiation due to the absence of ozone.
These reactions are also relevant in other environments exposed to UV radiation.
Currently, photochemical reactions in anoxic environments are performed using a 1000 W xenon
lamp and a specially made quartz reaction vessel. The xenon lamp supplies UV radiation while
the sealed reaction vessel maintains an anoxic environment. Siderite (FeCO3), marokite
(CaMn2O4), and ferrous chloride have previously been irradiated under these conditions.
Previous work has shown that the irradiation of siderite and ferrous chloride produces H2 gas,
more oxidized iron minerals, and simple organic compounds (Getoff, 1963; Braterman et al.,
1984; Joe et al., 1986; Kim et al., 2013). Current work on aqueous manganese (II), rhodochrosite
(MnCO3), and iron (II) smectites shows that these species are also photooxidized by UV light.
All three reactions produce H2 gas. The aqueous manganese (II) reaction also produces birnessite
(Anbar and Holland, 1992). The mineral products of the rhodochrosite and smectite reactions are
still being investigated.
35
Refining Carbonate Leaching Methods for Radiogenic Sr Isotope Analysis
Eric J. Bellefroid and Noah J. Planavsky
Radiogenic strontium isotopes (87Sr/86Sr) have proven to be a practical indicator of global
weathering rates, and an effective tool for global chemostratigraphic correlation. This proxy’s
effectiveness however, hinges on measuring primary 87Sr/86Sr signals. Though a range of
geological materials are often used for 87Sr/86Sr analysis (e.g. Calcite hard-shelly fossils, barites),
whole-rock limestones are the most widespread and best record of original seawater chemistry
for much of the geological record. Nevertheless, the utility of limestones has been limited as
alteration during diagenesis and contamination from silicate phases have been consistent
problems (e.g. Brand et al., 2012). Minor contamination or alteration should be straight-forward
to track and back-calculate using traditional geochemical alteration proxies. However, in many
successions, samples are afflicted by both diagenesis and contamination, making backcalculations difficult. Thus authors must often rely on least-altered samples without a firm grip
on the true degree of alteration or contamination.
Building on previous work (Liu et al. 2013), we have developed an improved sequential leaching
method which effectively separates carbonate phases from silicate contamination, and allows for
geochemical back-stripping of primary pristine 87Sr/86Sr values. Examining three separate case
examples, we first extract pristine marine 87Sr/86Sr values from altered whole-rock limestone and
show that we can replicate coeval brachiopod 87Sr/86Sr. We then show that even in samples with
high silicate matrix, primary carbonate 87Sr/86Sr can be back-calculate. Lastly, we show a rare
example where alteration drives 87Sr/86Sr to unradiogenic values and we then back-calculate
primary 87Sr/86Sr. Overall, this improved method increases the quality and reliability of 87Sr/86Sr
analysis, expanding the utility of this tool.
36
Microfossils from the Cryogenian Period of the Rasthof Formation, Namibia
Kimberly Du
Recent investigations of Cryogenian Rasthof Formation microbial carbonates from the
Fransfontein Ridge of northern Namibia reveal specimens with two distinct morphologies: oval
testate structures (~100-150µm) and tubular forms (~100-150µm). These samples are shallow
water stromatolites formed during the glacial interlude of the Cryogenian Period, a period of
extreme global warming following the older Sturtian glaciation (~750-700 Ma). While the testate
structures resemble forms previously identified from the Rasthof Formation, some of the tubular
morphologies are new. Analyses of the structures using energy dispersive x-ray spectroscopy
show that the elemental composition of the minerals on the surfaces of the ovals are composed of
aluminum, silica, oxygen, potassium and magnesium. The elemental composition of the tubeshaped specimens are almost exclusively aluminum, oxygen, and silica, and these along with the
structure of the minerals suggest that these microorganisms have been fossilized by kaolinite, a
common clay material formed from chemical weathering. The oval tests are consistent in shape
and size with agglutinated testate amoeba, similar to those previously reported from the Rasthof
Formation. Some of the tubular structures resemble previously reported agglutinated
foraminifera from the Rasthof Formation, but unlike previous finds, many of the structures found
in these samples preserve branches of tubes. Further work will determine the biological affinities
of these structures and what their preservation reveals about the postglacial marine
environments. Taken together, these fossils reveal a thriving benthic ecosystem of
microorganisms in the aftermath of the global Sturtian glaciation.
37
A new estimate of detrital redox-sensitive metal concentrations and variability
in marine sediments
Devon Cole, Shuang Zhang, and Noah Planavsky
Redox sensitive trace metal enrichments and depletions in marine sediments have been used
extensively as paleoredox proxies. The trace metals in shale are comprised of both detrital
(transported or particulate) and authigenic (precipitated, redox-driven) constituents, potentially
complicating the use of this suite of proxies. Untangling the influence of these components is
vital for the interpretation of enrichments, depletions, and isotopic signals of iron (Fe), chromium
(Cr), uranium (U), and vanadium (V) observed in the rock record. Traditionally, a single crustal
average is used as a cutoff for detrital input, and concentrations above or below this value are
interpreted as redox derived authigenic enrichment or depletion, while authigenic isotopic signals
are frequently corrected for an assumed detrital contribution. Specifically, in the Proterozoic,
enrichments tend to be small, leading to further difficulty distinguishing these components.
Building from an extensive study of soils across the continental United States – which upon
transport will become marine sediments – and their elemental concentrations, we find large
deviations from accepted crustal averages in redox-sensitive metals (Fe, Cr, U, V) compared to
typical detrital tracers (Al, Ti, Sc, Th) and provide new estimates for detrital contributions to the
ocean. The variability in these elemental ratios is present over large areas, comparable to the
catchment-size of major rivers around the globe. In cases where enrichments remain ambiguous,
the application of emerging isotope systems can provide a means to improve the resolvability of
trace element enrichment redox proxies, and the coupled use of these tools will be a major step
forward in our ability to understand a spectrum of redox environments.
38
Microbial Communities in a Meromictic Lake
Kristin Yoshimura, Jennifer Biddle, and Svetoslava Todorova
St. Glacial Lake is a meromictic lake in Onondaga County, NY, that exhibits patterns of seasonal
well-mixing in the surface layers, but extreme stratification at deeper depths. 16S rRNA gene
amplicon analyses show that common aerobic freshwater bacteria reside in the shallower layers
while deeper layers are characterized by anaerobic sulfur oxidizing bacteria. Between these two
layers, anaerobic phototrophic bacteria reside in a narrow transition zone.
39
Nutrient & translation limitation effects on sulfur isotope fractionation
Ying Lin, Boswell Wing, and Peter Douglas
Studies of microbial sulfate reduction (MSR) have examined the correlation between cellspecific sulfate reduction rate (csSRR) and sulfur isotope fractionation. Despite being subject to
environmental, strain-specific and metabolic differences, csSRR is generally negatively
correlated with enhanced 34S-32S differences and is considered a major influence on the relative
depletion of 34S during MSR in the natural environment.
Although variations in temperature, carbon type and quantity, and species identity can all
influence the relationship of sulfur isotope fractionation to csSRR during MSR, previous work
has not examined this relationship from the perspective of nutrient limitation versus translation
inhibition.
Our study explores the link between 34S-32S fractionation and csSRR in experiments that vary
csSRR by nutrient limitation or by translation inhibition. We forced a model sulfate-reducing
organism (Desulfovibrio vulgaris Hildenborough, DvH) to fix N2 as its only nitrogen source,
thereby limiting growth by throttling nutrient supply. We also subjected DvH to translation
inhibition via a sub-lethal dose of chloramphenicol, which interferes directly with ribosome
function. Both of these experiments reduced csSRR by ≈50% compared with growth of DvH
under nutrient-replete, antibiotic-free conditions. In our presentation, we will discuss these
results in light of our ongoing measurements of 34S-32S fractionation in these experiments.
40
Active microbial communities in Baltic Sea Basin sediments
Laura A. Zinke, Brandi Kiel Reese, Jordan Bird, Ian P.G. Marshall, Bo Barker
Jorgensen, Karen G. Lloyd, and Jan P. Amend
The Baltic Sea is shallow intracontinental sea that receives marine input from the North Sea and
riverine input from Scandinavia and continental Europe. This input contributes to high
sedimentation rates in the basin, which results in organic rich anoxic sediments. In 2013, the
Integrated Ocean Drilling Program Expedition 347 collected deeply buried sediment from the
Baltic Sea Basin for paleoclimatological and microbiological research. Here we present analyses
of the active resident microbial communities from three samples. We used metatranscriptomic
sequencing of in situ RNA and determined that Chloroflexi and Atribacteria are the dominant
active populations in our samples. Functional analysis of the genes expressed demonstrates that
fermentation is a key metabolic process in these sediments. Cycling of carbon, nitrogen,
phosphorus is mediated through mainly assimilatory and degradative processes. Genes for cell
division are also expressed, indicating that a portion of the in situ microbial community is
actively dividing. This study supports the argument that microbes in the deep biosphere are alive,
active, and biogeochemically relevant.
41
Investigating controls on boron isotope ratios in shallow marine carbonates
Shuang Zhang, Michael J. Henehan, Pincelli M. Hull, R. Pamela Reid, Dalton S.
Hardisty, Ashleigh v.S. Hood, and Noah J. Planavsky
The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both
planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct
absolute values of pH, due to the prevalence of so-called vital effects. Shallow marine abiotic
carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement,
and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic)
time. In this study, we present boron isotope measurements from shallow modern marine
carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water
carbonates as pH archives, and to explore the role of microbial processes in driving nominally
‘abiogenic’ carbonate deposition. For Bahama bank samples, our boron-based pH estimates
derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud,
stromatolitic micrite and calcified filament micrite) are higher than the estimated modern meanannual seawater pH values for this region. Furthermore, the majority (73%) of our marine
carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH
values for this region. In shallow sediment cores, we did not observe a correlation between
measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is
a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH
estimates are lower than likely in situ seawater pH at the time of cement formation. This study
indicates the potential for complications when using shallow marine non-skeletal carbonates as
marine pH archives. In addition, variability in δ11B based pH estimates provides additional
support for the idea that photosynthetic CO2 uptake plays a significant role in driving carbonate
precipitation in a wide range of shallow water carbonates.
42
The CO2-dependence of carbon isotope fractionation in a dinoflagellate
employing Form II RubisCO
Elise B. Wilkes, Susan J. Carter, and Ann Pearson
The carbon isotopic composition of algal organic matter preserved in marine sediments provides
a window into the evolution of the global carbon cycle, including variations in atmospheric
pCO2. There has been recent interest in using the δ13C values of dinoflagellates, as recorded in
fossil dinocysts, as a new paleoceanographic proxy for pCO2. However, significant questions
remain regarding carbon isotope fractionation in dinoflagellates before this proxy can be applied
with confidence. We investigated εp as a function of aqueous CO2 concentrations ([CO2(aq)])
and growth rates (µ) in nitrate-limited chemostat cultures of the dinoflagellate Alexandrium
tamarense. εp values displayed a robust linear relationship with µ/[CO2(aq)] (r2 = 0.94) in
agreement with previous investigations of eukaryotic phytoplankton in chemostat cultures. A
maximum fractionation (εf) value of 27‰ was inferred from the intercept of the experiments,
representing the first value of εf characterized for an algal species employing Form II RubisCO.
The similarity between the εf value for A. tamarense and the value of ~ 25‰ converged on by
taxa employing Form ID RubisCO is surprising in light of theoretical predictions for catalytically
distinct versions of the enzyme. We also measured the carbon isotopic compositions of
dinosterol, hexadecanoic acid, and phytol from each experiment, observing different isotope
patterns for each biomarker class. The clear CO2-dependence of εp values in our experiments
strengthens the proposal to use dinocyst δ13C values for constraining pCO2 in the geologic past.
Moreover, our observation that whole-cell εf values are approximately constant across members
of the three ecologically prominent phytoplankton clades may help to explain the broad
uniformity of carbon isotope partitioning between organic and inorganic phases over time.
43
The Effect of the Cretaceous-Paleogene Extinction on Deep Sea Calcium
Carbonate Accumulation
Claudia Deeg, Brenna Getzin, and Sara Pruss
The Cretaceous-Paleogene (K/Pg) extinction event was triggered by a large asteroid impact
~65Ma resulting in a marine diversity loss of nearly 50% at the generic level. Pelagic calcium
carbonate production (CaCO3) was reduced as a result of the extinction of pelagic calcifers.
Analysis of South Pacific cores from the Ocean Drilling Program (ODP) reveal anomalously
high carbonate accumulations across the K/Pg extinction boundary in the deep ocean. This
suggests that the carbonate compensation depth (CCD), the depth at which CaCO3 typically
dissolves in the ocean, was significantly lowered following the K/Pg extinction, possibly a
product of reduced primary production at the surface.
ODP Core U1370D from the south Pacific Ocean (41˚51.1156’S, 153˚06.3812’W) contains this
anomalous carbonate layer and samples from it were acquired and analyzed. Core U1370D
shows bulk material (<38μm) composed primarily of coccolithophores and coccolith fragments
in the fine fraction and planktic and benthic foraminifera in the >38μm fraction. The δ13C of the
planktic and benthic foraminifera (dominant species include Eoglobigerina edita, E. eobulloides,
Parasubbotina pseudobulloides, Praemurica nikolasi, Nuttallinella florealis, and Nuttallides
truempyi) is not significantly offset (both hover around 1.75 ‰), which suggests that carbon
isotope ratios of the Paleogene surface and deep waters were not notably different. The bulk
material, however, is isotopically heavy relative to the benthic and planktic forams (average δ13C
is 2.85 ‰) Our initial data from Core U1370D support the model of reduced primary production,
a slowdown of the biological pump, and a reduced surface ocean saturation state during this
interval, driving the collapse of the Pacific CCD following the K/Pg extinction.
44
Unusual Seafloor Precipitated Carbonate Fans of the Neoproterozoic
Rainstorm Member
Chiza Mwinde, Kristin Bergman, Marjorie Cantine, Blair Schoene and Sara Pruss
The Ediacaran Rainstorm Member of the Johnnie Formation hosts unusual carbonate seafloor
fans and records a very large negative carbon isotopic anomaly (e.g., Shuram anomaly)
correlated to similar anomalies documented in South Australia, Namibia, and South China. The
carbonate fan beds are concentrated at the base of the Rainstorm Member in a series of limestone
ledges. An unusual feature of these carbonate fans (up to 2 cm long), in particular, is the
concentration of heavy minerals that occur in the precipitate beds, including iron-rich minerals
and zircons. We concentrated a large population of detrital zircons by dissolving the carbonate
fans in dilute HCl, sieving the residues, separating out the magnetic minerals and performing
heavy liquid separation. LA-ICP–MS U–Pb dating of detrital zircons revealed a population of
zircons with ages younger than 800Ma, and further analysis of these may provide an additional
constraint and a more precise stratigraphic age of the Rainstorm Member.
Examination of the carbonate fans reveals some information on their depositional environments.
In thin section, the fans grow on erosional surfaces and in their interstices are concentrations of
the dark iron-rich minerals. A detailed XRD study of the fans and their surrounding sediments
shows that the fans formed in horizons with a substantial amount of hematite and titanium rich
sediments which may suggest sediment starvation during deposition. The presence of glauconite
in some samples also points to mixed redox conditions during fan deposition. Further work will
focus on examination of the fan settings and on the zircons hosted in these units to better
understand the stratigraphic age and environmental conditions present during the deposition of
the Rainstorm Member.
45
Mercury chemostratigraphy leading into the Sturtian Snowball Earth
glaciation: a volcanic aerosol link between volcanism and global glaciation?
Christopher Hodge, David Jones and Francis Macdonald
The Franklin large igneous province (LIP) was emplaced synchronously with the onset of the
Sturtian Snowball Earth glaciation, and two hypotheses of a causal link have been proposed. The
first attributes cooling to the drawdown of atmospheric CO2 resulting from the weathering of
fresh basalt erupted in the wet tropics, whereas the second attributes it to an increase in albedo
resulting from the stratospheric emission of sulfur aerosols. The former hypothesis predicts a
million to multi-million year timescale for cooling, whereas the latter predicts a decadal
timescale. Because volcanism releases mercury with an atmospheric residence time sufficient for
worldwide dispersal which later accumulates in marine sediments, Hg chemostratigraphy can
serve as a proxy for volcanism. Consequently, Hg has the potential to distinguish between multimillion year and decadal forcings. Here we report Hg concentrations from the Copper Cap
Formation of the Coates Lake Group in the Mackenzie Mountains. The Copper Cap consists of
>200 m of thin-bedded limestone in normal graded beds deposited predominantly below wave
base. A sharp sequence boundary is commonly present between the Copper Cap and glacigenic
deposits of the Rapitan Group, yet as much as 100 m of stratigraphy is preserved between the ca.
730 Ma Islay δ13C anomaly and the onset of the Sturtian glaciation at ca. 717 Ma. Most of the
Copper Cap is characterized by Hg concentrations below 50 ppb. However, Hg concentration
exceeds 280 ppb in strata immediately underlying the Rapitan Group. Although the duration of
the hiatus represented by the sequence boundary below the Rapitan is unknown, these
preliminary data are tentatively interpreted to indicate a rapid cooling response to LIP volcanism,
suggesting that volcanic aerosols may have initiated glaciation via increased albedo. This study
provides indirect geochemical evidence that the albedo effects of volcanism should be
considered in models of extreme climate change.
46
Triple oxygen isotope systematics in the global sulfur cycle
Anna Waldeck and David Johnston
The global sulfur cycle is largely seen as being driven by microbial processes in the ocean and
marine sediments. However, sulfur cycling and the composition of major reservoirs, like sulfate,
is also dependent on terrestrial weathering rates, iron availability, and hydrothermal circulation.
The sulfur cycle is as a result dynamic, and often tracked via the isotopic composition of sulfate
in the oceans. Interpretations aside, there is a rich record of sulfate isotope evolution over the last
120 Ma contained marine barites (BaSO4). Current sulfur cycle models use δ34S and δ18O from
barite to make assumptions about changes in Earth’s climate, particularly major fluxes like pyrite
burial and sulfide oxidation. Although powerful, using the δ34S and δ18O provides non-unique
solutions and leaves many features of the Cenozoic – Cretaceous record unexplained. This is
largely due to uncertainties about the isotopic fractionation associated with each process within
this cycle. Here I will extend these previous sulfur cycle models – both in scope and model
topology – using these barite records and the composition of modern marine sulfate as a target.
The 17O isotope carries different information from 18O, but does carry a level of isotopic
predictability (i.e. fractionations within the ocean are strictly mass-dependent). With this
approach I will attempt to differentiate between each of the primary processes that set the
isotopic composition of marine sulfate. This interpretation can then be extended to geological
records. We find that many of the changes in the sulfate record can be explained by variability in
global microbial sulfate reduction rates. Ultimately, building and interpreting the Δ17O record of
barite will deepen our understanding of climate stability over the last 120 million years.
47
Microbial alteration of the hydrogen and carbon isotopic composition of nalkanes in sediments
Alex Brittingham, Michael Hren, and Gideon Hartman
The hydrogen (δD) and carbon (δ13C) isotope compositions of long-chain n-alkanes provide a
record of paleoenvironmental conditions. At present, the role bacteria play in altering the stable
isotope composition of n-alkanes during storage of sediments is unclear. We collected four
sediment samples at precise depth intervals from an archaeological site and stored these samples
at room temperature for three years. Then, we collected sediment from identical locations
(measured to the cm level) three years later and froze these immediately. Samples stored at room
temperature showed high amounts of medium-chain n-alkanes (n-C18–n-C26), which were absent
from samples that were immediately frozen, and a decrease in the abundance of long-chain nalkanes (n-C27–n-C33). Measured δD values of n-C29 and n-C31 n-alkanes increased in stored
samples by up to 25‰. δ13C values in stored samples are more negative than non-stored samples
by up to 4.2‰. DNA analysis of the soil microorganisms showed bacteria containing genes
coding for n-alkane degrading enzymes proliferated in samples during their three year storage. In
particular, Rhodococcus and Aeromicrobium, genera which contain multiple coding regions for
the n-alkane degrading enzymes CYP153 and AlkB, increased by an order of magnitude (from
0.7% to 7.5% of bacteria present). These data suggest that bacteria may play a larger role than
previously expected in altering measured n-alkane stable isotope values during storage. We
recommend that sediment samples that are exposed to significant changes in oxygen or ambient
moisture after collection are extracted as soon as possible or stored refrigerated or frozen.
48
Linking Laurentia’s Latitude to Neoproterozoic Diversification of Eukaryotes
Athena Eyster, Benjamin Weiss, Karl Karlstrom, and Francis Macdonald
The late Neoproterozoic Era is marked by an evolutionary radiation of eukaryotic organisms that
culminated in the explosion of life. It has been suggested that Neoproterozoic tectonics may have
helped in stimulating this diversification of life. The Laurentian Chuar Group of the Grand
Canyon provides a spectacularly exposed record of shallow to deeper water environments
hosting rich biota including cyanobacteria, acritarchs and vase-shaped microfossils. Thus, study
of the Chuar Group can allow for testing links between tectonics and biological changes. In order
to quantitatively test these connections, paired paleomagnetic and geochronologic data are
necessary.
Here we present new paleomagnetic data from the Galeros and Kwagunt Formations of the
Chuar Group and from the overlying Sixtymile Formation integrated with new and existing
geochronologic constraints. We suggest that a hematite overprint may not have been fully
isolated in previous studies, causing a higher latitude bias in directions considered primary. This
new data suggest that Laurentia was anchored at lower latitudes and that this dependability may
have helped foster stable ecosystems allowing for increasing Neoproterozoic biocomplexity and
diversity.
49
Well-preserved marine carbonates record the oxygenation with the rise of
land plants
Ashleigh Hood, Malcolm W. Wallace, Alice Shuster, Christopher Reed and Noah
Planavsky
The late-Precambrian oxygenation of the ocean-atmosphere system is considered a major factor
in the environmental upheaval and associated diversification of animals in the Neoproterozoic.
However, while this Neoproterozoic Oxygenation Event is assumed to have pushed the Earth’s
atmosphere and oceans to modern-like O2 conditions, limited paleo-redox work has been done
more broadly spanning the Precambrian-Paleozoic boundary. A new perspective on marine
oxygenation during this time can be obtained through the application of rare earth element (REE)
and Ce-anomaly proxy work in well-preserved marine carbonates. Shale-normalised REE
profiles in marine carbonates are a commonly used paleooceanographic proxy and the presence
of a negative Ce anomaly is developed only in well-oxidised settings. Therefore REE profiles
and Ce anomalies preserved in marine carbonates can be used to track the oxygenation of the
oceans. Initial laser ablation ICP-MS work on multi-phase carbonate lithologies suggests that
diagenetic alteration may significantly modify REE profiles. Therefore, detailed petrographic
analysis and cathodoluminescence microscopy were required to characterise the preservation of
marine carbonate components in each sample. A range of well-preserved marine cements and
other components from the early Neoproterozoic to present were analysed by laser ablation ICPMS and combined with literature data (in studies where sedimentological analysis had been
undertaken). A new record of the Ce anomaly through this time period reveals that while
transient marine oxic conditions (moderate negative Ce anomalies) are recorded in the
Ediacaran, a return to large-scale anoxia occurs over much of the Paleozoic. It is not until the late
Devonian, co-incident with the rise of large, land plants and forest ecosystems, that modern-like
REE profiles and true negative Ce anomalies develop in shallow marine seawater. This data
suggests that the establishment of abundant terrestrial vegetation.
50
Temperature records from Marinoan-age low latitude carbonates
Adam Jost and Kristin Bergmann
The Marinoan glaciation (ca. 639–635 Ma) occurred soon after the emergence of early complex
multicellular eukaryotes and before the diversification of large Ediacaran fauna. However, our
understanding of how this Snowball Earth episode impacted life is limited by sparse data from a
narrow suite of geochemical proxies. To better characterize the climate and depositional history
of this interval, we measured carbonate clumped isotopes in rocks from the Wilsonbreen
Formation. This sequence of well-preserved end-Marinoan synglacial deposits from Svalbard
includes both primary carbonate facies and diagenetic cements now preserved as either limestone
or dolomite. We sampled carbonate microfacies within samples from throughout the sequence to
determine δ13C, mineral δ18O, and the δ18O and Δ47-derived temperature of the precipitating
fluid. Preliminary data demonstrates that different microfacies within a single sample can yield
precipitation temperatures which vary on the order 100°C, emphasizing the importance of fabric
selective recrystallization and the need for careful characterization of specific carbonate fabrics.
Minimum temperatures are low (<15°C), consistent with near-freezing conditions at equatorial
latitudes.
51
Reinterpretation of putative tintinnid lorica fossils from the Neoproterozoic
Tsagaan Olom Group, Mongolia
Maoli Vizcaíno, Phoebe Cohen and Ross P. Anderson
The Neoproterozoic Era was an important time for life on Earth, as this was when the major
lineages of eukaryotes originated and diversified while simultaneously surviving global
glaciations during the Snowball Earth events. Carbonate successions have become an important
new taphonomic window into the fossil record of Neoproterozoic eukaryotes. One of the most
notable examples is the ca. 662–635 Ma Taishir Formation (Tsagaan Olom Group, Zavkhan
Terrane, Mongolia). Here, we examine more closely the morphology and potential taxonomic
affinity of organic eukaryotic fossils previously interpreted as remains of ciliate tintinnid loricae
from the Taishir Formation and the overlying Ediacaran Ol Formation of the Tsagaan Olom
Group via physical measurements of the fossils. We examined 230 samples from the Taishir
formation and found that only 18 contain fossils of these putative ciliates. We demonstrate that
the fossils’ original interpretation as ciliate organisms may need revising in light of new
ultrastructural data coupled with comparisons to macroscopic organic warty sheets (MOWS).
MOWS were identified within the Taishir formation by Cohen et al. (2015) and interpreted as
putative marine red algae fossils. Our new comparison suggests that instead of ciliates, these
fossils may be red algal reproductive structures and thus related to the coeval MOWS fossils. A
new interpretation of the fossils in this study will have broader implications for our
understanding of biodiversity in the Neoproterozoic.
52
Two pulses of oceanic environmental disturbance during the Permian–
Triassic boundary crisis
Jun Shen and Noah Planavsky
The Permian–Triassic transition is a key interval in Earth history owing to long-lasting,
concurrent, and interrelated changes in the biosphere and environment. There is evidence for two
extinction events geochemical perturbations, a Latest Permian event (1st extinction, equal to Bed
25 at GSSP Meishan D section), and the Early Triassic event (2nd extinction, equal to Bed 28 of
GSSP Meishan D section), based on the abundance high-resolution paleontological work and
geochemical studies. We integrated pyrite morphology, iron speciation, and pyrite sulfur isotope
to explore the oceanic environmental variations near the Permian-Triassic transition in Xiakou
section, South China, which was located in deep shelf environment and has a detailed
biostratigraphy. Oceanic redox conditions were euxinic during the pre-extinction Late Permian,
as characterized by high ratios of highly-reactive iron to total iron (FeHR/FeT>0.6) and pyrite
iron to highly-reactive iron (FePy/FeHR>0.7) together with a high abundance of small (mean
diameter <5μm) framboidal pyrite, and subsequently fluctuated between ferruginous/suboxic and
euxinic during and following the extinction interval, yielding high ratios of FeHR/FeT(mostly
>0.6) along with lower values of FePy/FeHR(<0.7) and more variable framboid sizes and
morphologies. The most continuous and intense euxinic episodes were associated with the 1st
and 2nd extinction horizons, respectively of latest Permian and earliest Triassic age. The two
euxinic intervals associated with an extinction pulse at Xiakou coincided with deposition of
rather extensive volcanic ash layers that have been correlated w
53
Prospects for Bamboo Corals as Barium-based Archives of Bathypelagic
Ocean Circulatory Structure
Ben Geyman, Tristan Horner, Jamie Ptacek, Maureen Auro, Tessa Hill, and Michèle
LaVigne
The scarcity of instrumental and geochemical records from ocean oxygen minimum zones limits
our understanding of relationships between circulation and biogeochemical cycling in these
regions. Of particular interest are geochemical tracers for past meso- and bathypelagic
circulation, as these depths often harbor large oxygen-minimum zones. Deep-sea bamboo corals
are well equipped to address this scarcity due to their longevity, distribution throughout the
bathypelagic, and ability to record the chemistry of ambient seawater in their calcite skeletons.
In this study we assess the fidelity of bamboo corals to record the concentration and isotopic
composition of dissolved Ba (barium) in seawater, which has been shown to behave
conservatively in the deep Atlantic Ocean. To ensure that the corals record dissolved Ba(II)
rather than particulate Ba phases, such as barite, we performed a series of stepped chemical
cleaning and imaging experiments that indicate that essentially all Ba is hosted in corraline
calcite. We then compared a suite of corals, collected live from the California Margin between
870 and 2,100 m, against newly generated profiles of North Pacific Ba distributions. We find that
bamboo corals reliably record depth-dependent changes in seawater barium concentrations and
isotopic compositions via a constant Ba partition coefficient and stable isotopic offset,
respectively. We use this calibration to explore putative links between circulation, nutrients, and
oxygen in the bathypelagic North Pacific over the past century.
54
Understanding oxygen isotope trends during microbial sulfate reduction: A
new approach integrating pure culture experiments, statistical tools, and
steady state isotope models
Emma Bertran, Anna Waldeck, Boswell Wing, Itay Halevy, and David Johnston
The stable sulfur (S) and oxygen (O) isotopic composition of sulfate provides key insight into the
reconstruction of both modern and paleo-environments. Positive correlations in the changes in
δ34Ssulfate and δ18Osulfate resulting from microbial sulfate reduction indicate different, but related
intracellular biochemistry. Often, sulfur isotopes are used to constrain reductive fluxes, whereas
oxygen isotope effects are thought to inform oxidation. Despite a rich literature of documented
environmental and microbial isotope effects, a framework that accommodates both S and O
isotope effects while explaining the range of observations remains elusive.
Here we present results from a series of continuous culture experiments of two strains of sulfate
reducing bacteria grown across a range of conditions. These data illustrate a δ18Osulfate value that
was constant across experiments, and averaged to 11.0 ‰ (1σ = 0.8 ‰). We use this dataset in
combination with a modified reaction network for oxygen isotope fluxes during microbial sulfate
reduction to draw explicit relationships between intracellular reaction reversibility, their specific
isotope effects, and net fractionation factors. This reaction network is that of Wing and Halevy
(2013), extended to oxygen (explicitly accounting for phosphate and water incorporation) while
conserving flux balances required to satisfy S isotope observations. As this system is
underdetermined, we use resampling algorithms to solve for step-specific oxygen isotope effects.
These are in turn used as input into previously established quantitative steady state isotope
models to reconcile pure culture and environmental trends while satisfying both δ18Osulfate and
δ34Ssulfate measured during the experiments.
55
Calcium isotopes in elasmobranch teeth as a window into modern and ancient
marine ecology
Alliya Akhtar and John Higgins
Understanding the complex interactions between environmental change and the ecological
structure of marine systems on decadal timescales and longer requires an approach that can
access geological archives. Studies of calcium isotopes (44Ca, 43Ca, 42Ca, 40Ca) in modern and
fossil marine organisms is promising in this regard as early studies have shown that the ratio of
these isotopes (i.e. 44Ca/40Ca) in bones and teeth are related to trophic level (Skulan and DePaolo,
1999; Martin et al., 2015). Elasmobranchs represent an ideal candidate for calcium isotope
analyses due to their global distribution, long temporal range, as well as high species level
diversity in both modern as well as fossil assemblages. The 44/40Ca of the enameloid component
of shark teeth is reflective of both the 44/40Ca of the seawater at the time of precipitation, and the
respective trophic level of the individual, as sharks occupy a range of feeding ecologies from
zooplanktivores to tertiary consumers. Analyses of 60 modern teeth representing 21 species yield
an average 44/40Ca of -2.040.49 ‰. In agreement with trends reported in previous studies (Skulan
et al., 1997; Skulan and DePaolo, 1999; Martin et al., 2015), we observe a slight decrease in
44/40
Ca with increasing trophic level. Combining 44/40Ca analysis with measurements of other
geochemical proxies (e.g. Sr/Ca, Mg/Ca, magnesium isotopes) will help elucidate 1) whether
enameloid 44/40Ca captures a significant trophic level signature, and 2) if these signals can be
used for reconstructions of ancient ecosystems via fossil teeth, as well as the implications for
reconstructing ancient seawater 44/40Ca.
56
Constraining Mesoproterozoic oxygen levels through the multiple sulfur
isotope stratigraphy of the Bylot Supergroup, Baffin Island, Nunavut
Kelsey G. Lamothe, Peter W. Crockford, Marcus Kunzmann, Malcolm S.W. Hodgskiss,
Timothy Gibson, Sarah Worndle-Quoex, and Galen P. Halverson
Understanding the oxygenation of the mid-Proterozoic (1.8-0.8 Ga) atmosphere and oceans is
important for studying the possibility of a link between animal evolution and oxygen levels.
Recent work using chromium isotopes appears to have presented conflicting results, with large
isotopic fractionations indicative of an oxygenated surface environment above 0.1% of the
present atmospheric level (PAL) only appearing in shales younger than 0.8 Ga, but appearing in
carbonates as old as 1.1 Ga. This discrepancy either highlights transient oxygenation events, or a
discrepancy between different geologic archives. Here we present the results of our study using
multiple sulfur isotopes to investigate this inconsistency. When atmospheric O2 levels are above
5% PAL, reoxidative S-cycling leaves a detectable bacterial disproportionation signal in the
multiple S isotopes of authigenic pyrite. We have collected and analyzed S isotope data from
shales spanning the entire Meso- to early Neoproterozoic Bylot Supergroup (ca. 1.1 to 0.8 Ga), a
~6 km thick sedimentary succession on Baffin Island. Our results show no disproportionation
signal in any of the samples, demonstrating that during the deposition of the Bylot Supergroup,
O2 levels did not reach the 5% PAL threshold to imprint the geologic record with an S
disproportionation signal. This maximum constraint provides a starting point from which we can
further narrow down the evolution of Mesoproterozoic atmospheric O2 using different
geochemical proxies.
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Geochemical fingerprints of maximum flooding surfaces in the >811 Ma
Fifteenmile Group, Yukon reflect the iron shuttle
Timothy M. Gibson, Marcus Kunzmann, Galen P. Halverson, and André Poirier
We have performed a multi-proxy bulk-rock geochemical study (δ56Fe, Fe speciation, major and
trace elements) spanning maximum flooding (MF) intervals within the >811 Ma, mixed
carbonate-shale Reefal assemblage of the upper Fifteenmile Group in Yukon, northwestern
Canada, to evaluate the role of relative sea level fluctuations on redox conditions and Fe cycling.
The maximum flooding intervals are characterized by very fine-grained and finely laminated
mudstones with relative high %TOC and low FeT/Al and FeHR/FeT. The transition above the
MF intervals, which reflects shoaling at the beginning of the highstand systems tract (HST),
shows a sharp decline in %TOC and rise in FeT/Al and FeHR/FeT, as well as enrichments
redox-sensitive trace metals. Iron isotope compositions are inversely correlated with FeT/Al and
FeHR/FeT, exhibiting inverse stratigraphic trends across the MF intervals. We interpret these
patterns to record the influence of the benthic iron shuttle, whereby 56Fe-depleted iron is
reductively mobilized from mudstones during sea level maxima, when high relative sea level,
low sedimentation rates, and high organic carbon flux result in anoxic conditions at the
sediment-water interface. As these conditions retreat and dissipate during the HST, a return to
oxic bottom waters results in an accumulation of 56Fe-depleted iron and trace metals released
from anoxic sediments immediately downslope. These results demonstrate that, at least during
periods of high sea level, anoxic conditions prevailed below the surface mixed layer on
continental shelves, and the iron shuttle, driven by dissimilatory iron reduction, was vigorous in
the early Neoproterozoic. Furthermore, fluctuations in relative sea level in the presence of a
strong redox gradient generates large variations in redox proxies which do not directly reflect
changes in the redox state of the global ocean.
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Stratigraphy and paleoenvironments of the Kellwasser Events in the Upper
Devonian of the Southern Tier of New York and north-central Pennsylvania
J. Andrew Beard, Michael T. Hren, Andrew M. Bush
Upper Devonian strata in the northern Appalachian Basin record two pulses of extinction
coincident with the deposition of organic-rich shales: the Lower Kellwasser Event (LKW) and
the Upper Kellwasser Event (UKW). Studies from numerous localities worldwide indicate that
the LKW and UKW were accompanied by ~3-4‰ positive δ13C excursions, ocean
anoxia/dysoxia, and global cooling. Anoxia and cooling are commonly discussed kill
mechanisms, but further study is needed to better evaluate what the primary driver of extinction
was. We have been working on the LKW-UKW interval in highly fossiliferous, storm-dominated
shallow-marine paleoenvironments of New York and Pennsylvania. Shallow-marine settings
have been understudied for the LKW and UKW, but are essential for understanding the extent of
anoxia and the biotic response to extinction. Here, we present current results based on
examination of numerous sections through the LKW and one through the UKW, including
stratigraphic revisions, δ13Corg stratigraphy, facies analysis, and preliminary data on oxygen
levels in the LKW and UKW based on paleontological and XRF analyses. Our preliminary
results, combined with work by others in deeper parts of the basin, suggest that, at the very least,
anoxia was not temporally persistent during deposition of the LKW. Further work will better
constrain oxygen levels in a range of paleoenvironments.
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Microbial Analysis, Resources, and Services (MARS), UConn CORE
Kendra Maas
The Microbial Analysis, Resources and Services (MARS) facility supports the research
community of the University of Connecticut specializing in the analysis of microbial samples
and high-throughput processing of nucleic acids. Examples include the characterization of
microbiomes (Bacterial V4 or custom amplicon), sequencing of small genomes, 96-well and
384-well PCR setup or DNA quantification and other automated liquid handling applications.
Services are available a la carte, ranging from fee-for-service to unassisted use of the equipment
by trained and certified users. Researchers external to UConn are also welcome to submit
samples for processing and use our equipment in Storrs.
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No safer in the south: The Cretaceous–Paleogene (K–Pg) mass extinction
event and recovery in Antarctica
James D. Witts, Rowan J. Whittle, Paul B. Wignall, J. Alistair Crame, Jane E. Francis,
Robert J. Newton, Vanessa C. Bowman
The Cretaceous–Paleogene (K–Pg) mass extinction of 66 Ma is a key event in Earth history, with
extinction of many previously dominant terrestrial and marine groups. There has been much
debate about the nature (and causes) of this mass extinction, and its effects. Questions remain as
to whether the pattern of extinction is consistent with a catastrophic driver such as asteroid
impact, or a more gradual crisis with volcanism and climate change playing a role. There are also
persistent ideas that high latitude ecosystems may have coped better during the extinction, and
exhibited a rapid recovery in the Paleocene.
The highest southern latitude onshore K–Pg boundary is located on Seymour Island, Antarctica
(65°S today, and during the Late Cretaceous and Paleocene). Here, a thick and fossiliferous
Maastrichtian–Danian (~70–65 Ma) sedimentary succession is preserved within a back-arc
sequence of marine siltstones and sandstones to the East of the Antarctic Peninsula.
New paleontological data (primarily based on marine molluscs) from a ~1400 m-thick composite
stratigraphic section across the K–Pg boundary show fluctuations in the diversity and richness of
the marine fauna are related to a combination of regional (water depth and redox), and global
(sea level, climate and temperature) paleoenvironmental changes. A single extinction event
occurred at the K–Pg boundary. Initial recovery of marine ecosystems in the Paleocene took
~300 kyrs, and recovery of species richness in some groups to pre-extinction levels up to ~1
million years. This is the same timescale as recovery of the global carbon cycle, suggesting
strong biosphere-geosphere links. These new data do not support claims for either a gradual or
double extinction pulse in Antarctica, and suggest the tempo, severity, and effects of the K–Pg
mass extinction and recovery in continental shelf settings were likely the same across all
latitudes.
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