Jennifer Glass has received a NASA Postdoctoral Fellowship to work with Victoria Orphan at Caltech, beginning summer 2011. Victoria Orphan has interests in molecular microbial ecology of anaerobic communities involved in carbon and sulfur cycling and develops and applies molecular and isotopic methods for relating uncultured microorganisms to biogeochemical processes and understanding interspecies interactions. Specific research interests include microbial community structure and function in deep subsurface habitats, marine sediments, oil and gas seeps, and early Earth analog environments. Congratulations, Jen!
Improved understanding of climate-change consequences in the ocean will come from technological advances and new interdisciplinary efforts. We plan to combine connectivity ecology, metal isotope geochemistry, and paleoclimatology to identify new proxies for ocean acidification. These will be used to assess pH exposures in living organisms (e.g., squid and mussels) and, potentially to interpret the geologic record. The approach is based on the hypothesis that the isotopic composition of larval calcium carbonates reflects changes in seawater chemistry driven by ocean acidification and, in some instances, with associated decline in oxygen levels. The integration of pH and oxygen in proxy development should provide important insights about climate-induced stress on the early life stages of marine organisms.
We bid a fond farewell to Carina, Laura, Stan and Yun from our group, and welcome Christy Meza and Sayantan Das.
Carina has left to pursue her PhD at theUniversity of Cordoba, one of the most prominent educational institutions of her native Argentina. Laura Wasylenki has accepted an Assistant Professorship at the Geological Sciences department of Indiana University at Bloomington. Stan is now working as Chris Skiba's right-hand man in keeping the entire SESE facility operating smoothly. Yun successfully completed her PhD in spring 2010 and has gone on to begin a program in physical therapy.
Christy Meza comes to us with a BS in biology from the University of Nevada, Las Vegas and five years experience at a Las Vegas wastewater treatment plant assisting researchers investigating the impact of hormones and trace metals on fish, among other research. Sayantan Das comes as a new doctoral student from the Chemistry department and is interested in the development of oxygen in the early Earth.
In many regions of the world's ocean, primary productivity is not limited by the major nutrients (nitrogen, phosphorous and silica) but by the micronutrient iron (Fe). One major source of Fe is the atmospheric transport and deposition of aerosols to the open ocean. The aerosols come from natural sources, such as soils and dust and biomass burning, and from anthropogenic emissions related to industrial processes and energy generation. Our understanding of the sources is limited by our ability to identify the origin of the Fe. Mechanisms of tracing the sources of aerosols include the use of the elemental ratios as specific sources have specific elemental signals. Fe isotopic variation has recently been demonstrated to be a potentially important tracer of Fe sources.
This project, a collaboration between investigators at Arizona State University and Northern Arizona University, will explore the use of Fe isotopes as a tracer of natural and anthropogenic sources of aerosols to assess their importance as a source of Fe to the open ocean. Fe is known to limit primary production in many high nutrient, low chlorophyll areas, so it is important to understand the origin of the Fe that is delivered to the oceans and its availability to marine microorganisms. Additionally, aerosols from different sources have variable size and solubility in seawater and therefore this also impacts Fe bioavailability. Examination of the isotopes of Fe in aerosols could help address these questions as the investigators' prior research has demonstrated distinct variations in the isotopic composition of aerosol Fe that arise from natural and anthropogenic sources.
The study will measure the Fe isotopic compositions of aerosol particles collected on Bermuda over a period of one year. Bermuda was chosen as seasonal differences lead to different aerosol types being deposited - summer winds flow from the east and carry Saharan soil dust and other aerosols, while winter winds originate from over North America. The project will compare the Bermuda results with that of key anthropogenic and natural aerosol materials that could be a source of Fe to the Atlantic Ocean. In addition, elemental analyses of these aerosols will provide an independent confirmation of the Fe isotopes results. Analysis of size-segregated samples will provide additional information and will be coupled with solubility experiments designed to assess the soluble Fe fraction.
Image borrowed from The Naked Scientists website.
On September 16th, 2010, Ariel gave a popular science talk related to "water" as the closing event for the installation "90 Days over 100 degrees" at the Scottsdale Museum of Contemporary Art.The installation is a walk-through involving melting and evaporation of water ("phase transitions") designed by an architect and an engineer. He discusses how researchers "follow the water" in searching for life beyond Earth, but how an "ocean planet" that has only water at the surface could be too much of a good thing.
Felisa was prominently featured on an episode of Through the Wormhole with Morgan Freeman, premiering on the Science channel on July 7, 2010 at 7 pm. For a video of her performance (with a guest appearance by husband Jonathan Simon!),
click here.
She was profiled for her work on isolating some organisms in Mono Lake, California that are tolerant to extraordinarily high concentrations of arsenic. Stay tuned, the publication is in submission to Science...
New geochemical data from the South African Agouron drill cores paint a clearer picture of oxygen distribution in the Late Archean marine environment! Rhenium and molybdenum abundances and sedimentary iron geochemistry in 2.6-2.5 Gyr old black shales indicate that photosynthetic production of oxygen by cyanobacteria was vigorous in the Late Archean surface ocean near the continents. Mildly oxygenated waters extended below the photic zone before giving way to anoxic deep and open oceans. Mass independent fractionation of S isotopes indicates that atmospheric oxygen abundances remained below 0.001% of the present atmospheric level. Our results show that substantial oxygen accumulation began along productive ocean margins more than 100 million years before the first significant increase in atmospheric oxygen concentrations. This research was a collaborative effort with Chris Reinhard and Timothy Lyons from the University of California (Riverside), Alan Jay Kaufman from the University of Maryland, and Simon Poulton from Newcastle University. The paper is now available in the September 2010 issue of Nature Geoscience.
FIGURE CAPTION: Simplified representation of the redox conditions along Late Archean ocean margins beneath a low-oxygen atmosphere (credit: Susan Selkirk). The orange cells in the inset figure are Synechococcus, a unicellular cyanobacterium only about 1 um in size (credit: Susanne Neuer/Amy Hansen). Organisms like Synechococcus were responsible for pumping oxygen into the environment 2.6-2.5 Gyr ago.
Uranium ore concentrates (UOCs) from around the world were measured for both 238U/235U and 235U/234U ratios. These isotopic signatures can reveal the type of geologic environment in which the uranium was deposited (238U/235U), as well as the extent of modern water/rock interactions (235U/234U). The pairing of these two systems on the same sample allows the a mine to develop a uranium isotope "fingerprint" which can be useful in cases of illicit smuggling of nulcear material.
Jennifer Glass has a new publication in Limnology & Oceanography entitled "Molybdenum-nitrogen colimitation in freshwater and coastal heterocystous cyanobacteria", coauthored with Anbar alum Felisa Wolfe-Simon, collaborator Jim Elser and Ariel Anbar. This work experimentally evaluates the sensitivity of several species of cyanobacteria to molybdenum and nitrogen limitation. Molybdenum (Mo) is a metal critical for nitrogen fixation, and the requirements for freshwater and salt water organisms might be expected to vary due to the more than five-fold Mo concentration decrease in freshwater compared to the ocean. Contrary to expectation, cyanobacteria from both environments were able to continue fixing nitrogen for more than a month even under low Mo conditions. Details of the rates of nitrogen fixation and chlorophyll content suggest that freshwater cyanobacteria were more robust in Mo-limited conditions due to gene expression of the Mo-storage protein mop.
An All Hands meeting of ASU's "Follow the Elements" Astrobiology group at ASU's Memorial Union on January 25-26th, 2010 brought together the many investigators on this grant from NASA's Astrobiology Institute. Two days of workshops, talks and poster sessions outlined the results already emerging from this exciting field of research, including Greg Brennecka's recent Science paper.
Other talks included The Stoichometry of LIfe - Lab, Field, Geology and Genomes (Jim Elser, lead); Astrophysical Constraints on the Elements of Life - 26Al, Water, Supernovae (Frank Timmes, lead); and Habitability of Water-rich environments - Mars, Europa, Enceledus, Titan and KBOs (Mikhail Zolotov, lead).
Updates on NASA Missions included presentations from Phil Christensen (Mars), Paul Scowen (Astronomy), Ron Greeley (Europa) and Dante Lauretta (asteroids). An undergraduate outreach event on the evening of January 26th was lead by Steve Desch.
Greg Brennecka is lead author on a paper appearing in the January 22nd, 2010 issue of Science. Coauthored with Stefan Weyer, Meenakashi Wadhwa, Phil Janney, J. Zipfel and Ariel Anbar, this paper measures the 238U/235U ratio in meteoritic material. This ratio has been assumed to be invariant, and is a critical assumption when calculating the age of the Solar System by the lead-lead dating method. These results show that the 238U/235U variations seen in these samples could cause miscalculation of the Solar Sytems oldest solids by as much as five million years. Calcium-Aluminum-rich Inclusions (CAI's) of the Allende meteorite have variable 238U/235U ratios, and correlations with curium analogs of thorium and neodymium suggests the variability is caused by decay of 247Cm to 235U in the early Solar System. This exciting result was profiled in a Science Perspective article by J.N. Connely in the same issue.
Ariel is a coauthor on four papers in the journal Science that have emerged out of study of sediments in Western Australia deposited during the Late Archean, 2.5 billion years ago These papers all provide evidence of trace amounts of O2 in the environment before the transition to a generally oxidizing atmosphere. The latest paper is in the October 30th issue. You can read about some of the results here. This latest work is in conjunction with collaborator Tim Lyons at University of California, Riverside and is first-authored by UCR grad student Chris Reinhard. The paper studies iron speciation in black shales, and demonstrates that the early oxygenation of the Earth system was more nuanced and variable than previously thought.
This summer we bid a sad goodbye to postdoc Brian Majestic, visiting scientist Tsuyoshi Komiya and undergraduate Bryan Rolfe, and welcomed postdoc Amisha Poret-Peterson and lab technician Carina Arrua. Brian left us for a position at Northern Arizona University in the Department of Chemistry and Biochemistry, while Bryan has continued on to pursue a doctorate in Chemical Engineering at Cornell. He hopes to pursue the topic of his NSF fellowship proposal, nanofluidic batteries. Komiya returns to his position as an Associate Professor at the Tokyo Institute of Technology. Amisha joins us from the University of Louisville, where she worked Professor Martin Klotz on nitrification genes in methane-oxidizing bacteria. Carina comes to us with a Masters from the Universidad Nacional de Córdoba in Argentina, where she used multivariate statistics to authenticate wines from several regions in Argentina. She will be assisting users in the clean lab and with measurements on the quadrupole ICP-MS in the Keck lab. Gabi Montanez is still at ASU, but is focusing on completing her Master of Science in Engineering (MSE) program in the School of Mechanical, Aerospace, Chemical and Materials Engineering.
Jennifer Glass's project has been selected for the NASA Astrobiology Institute/APS Lewis and Clark Fund for Exploration and Field Research. Her project is entitled "Evaluation of Molybdenum Diagenesis in Sediments of Castle Lake, California". Read about the prize and all the winning projects.
At the first meeting of the Astrobiology seminar of the Fall 2009 semester, Everett Shock outlined the importance of the Yellowstone hot spring ecosystem and reviewed the sampling design for the recent successful 2009 field season. Steve Romaniello then described the purpose and methodology of the experiments to look at the rates of nitrogen cycle steps by spiking incubated experiments with 15N. Come join us at this cutting edge exploration of the science of astrobiology!
Ariel, Steve, Hilairy, Stan, Everett, Amisha, Tracy and Chris (among others!) returned from a successful field season collecting samples in the hot springs of Yellowstone. These extreme environments inform us about the limits of life and what life in other parts of the solar system and beyond might be like. In fact, fall semester 2009, there will be a seminar series, "Hydrothermal Ecosystems" to allow students (and faculty!) to gain a greater appreciation of the system dynamics. Co-led by Everett Shock and Jeff Dick, the organizational meeting for this course was Monday, August 24th at 4 pm in PS-H 460.
Jennifer Glass completed a successful field season at Castle Lake collecting porewater, sediment core and water column samples at this glacial molybdenum-poor lake.
"When do black shales tell molybdenum isotope tales?" Geology vol 37 no 6, p. 535-538, doi: 10.1130/G25186A.1 appears in June 2009. Molybdenum isotopes in ancient black shales have been used to tell us about the amount of oxygen in the world’s oceans in the past. Lighter isotopes preferentially go into oxic sediments, while sediments laid down in water columns with high sulfide reflect the isotopic composition of the water. By looking at two similar sequences of Devonian rocks (~380 million years old), Gordon et al. constrain what types of organic-rich sediments record the signal from ancient seas. The evidence is consistent with larger areas of the seafloor with low oxygen in the middle Devonian.
A paper, by Gwyn Gordon with co-authors Matt Rockman (New York University), Karl Turekian (Yale) and Jeff Over (SUNY at Geneseo), appears in the May issue of the American Journal of Science ("Osmium Isotopic Evidence Against an impact at the Frasnian-Famennian boundary", AJS v. 309, p.420-430; doi:10.2475/05.2009.03). This paper demonstrates conclusively that there could not have been a global meteorite impact immediately prior or during this mass extinction boundary - one of the five largest in Earth's history. The paper examines two sites: one in upstate New York and the other in France. The upstate New York sequence measured ten depths below, at and above the boundary and derived an isochron that is consistent with other measurements of the boundary's age. This is the first direct measurement of osmium isotopes at the F-F boundary; the initial 187Os/188Os value of 0.49 ±0.16 is consistent with other estimates of marine Os isotopes for this period and demonstrates no indication of significant extraterrestrial material. Samples at La Serre, France, have highly enriched Os concentrations of greater than 33 ppb - the highest published Os concentrations for this boundary and more than two orders of magnitude higher than average shale - but the 187Os/188Os is highly radiogenic and indicates no addition of significant meteoritic material.
Jennifer Glass' new article entitled, "Coevolution of metal availability and nitrogen assimilation in cyanobacteria and algae" is in press at Geobiology. It can be found at DOI: 10.1111/j.1472-4669.2009.00190.x. Coauthored with Felisa Wolfe-Simon and Ariel Anbar, this publication represents an important advance in our understanding of how the oxygenation of the early Earth was reflected in biological evolution.