Hilairy Ellen Hartnett, PhD, MS, AB - US grants

Hartnett
0525569
Arid desert environments are home to a unique microbe-mineral system in which cyanobacteria and microalgae form biological soil crusts. These systems are important because they significantly impact the carbon cycle and nutrient budgets in arid regions, and because they may be representative of early terrestrial biota before the rise of land plants. Biological soil crusts exist in an environment profoundly limited by the lack of water and nutrients, especially bioessential trace metals. We hypothesize that biological soil crusts maximize their retention of water and nutrients through the production of organic compounds. The soil crust community's mediation of organic compounds and the bioessential metals in the soil provides a fundamental biogeochemical link between microbes and earth-materials. Our experimental studies focus on the interactions of soil crust microbes with mineral substrates, and the nature and effects of the organic compounds produced and/or lost to the soil porewater on metabolically relevant metals. Our specific objectives are: 1) To characterize desert soil crust and the underlying soil mineralogy and geochemistry; 2) To compare crusted and uncrusted soil systems with respect to carbon and trace element composition; 3) To simulate rain events and assess changes in biological soil crust organic carbon production and metal distributions before, during and after water exposure. Electrospray ionization tandem mass spectrometry will be used to identify specific organic compounds directly from water samples, and ICP-mass spectrometry will be used to determine trace metal concentrations and distributions. This integration of organic biogeochemistry, trace element biogeochemistry, and geomicrobiology is quite unusual and our graduate and undergraduate students will gain unique trans-disciplinary research experience.

Intellectual Merit: This research explores how geochemical processes support microbes living deep in the Earth. A major challenge in understanding how life can survive at depth is the identity and source of organic compounds that are consumed by microbes. While some of these compounds are likely to be produced by other subsurface microbes, this works focuses on the large inventory of consumable organic compounds that comes from geochemical transformations of organic matter that take place as sediments are buried and exposed to elevated temperatures and pressures. Goals of the work are to examine, both theoretically and experimentally, chemical reactions that occur at temperatures and pressures greater than microbial life can withstand. These high temperature and pressure reactions produce organic solutes that are transported upward into the inhabited zones of the subsurface. The primary focus of the research is to determine how reactions between hot water and organic matter generate small organic compounds that ultimately feed the deep biosphere. Phase I focuses on hydrothermal experiments of well-known reactions that transform simple hydrocarbons into alcohols, ketones, and carboxylic acids at elevated temperatures and pressures. Phase II explores these same reactions, but in the context of a more realistic and thus complex geologic system that includes the clay minerals found in all organic rich sediments and sedimentary rocks. Most of these reactions have not been systematically studied under geologically realistic conditions. As a result, our present understanding of these transformation mechanisms in nature are speculative. This work produces rigorous results from which calculations can be made to predict the microbial metabolic potential of areas deep within the Earth?s crust.

Broader Impacts: This work provides organic chemists with new methods to control reactions and provides geochemists with new predictive, mechanistic models of organic matter transformations. New models will inform those making site selections for future ocean and continental drilling efforts that explore the deep biosphere and will allow us to better understand the generation of petroleum. This project also provides a means to predict where prospecting of new microbial species with unusual properties can be found. The hydrothermal reactor approach may also provide green alternatives to incineration or burial of organic waste. In terms of education and training, the work supports post-docs, graduate students, and undergraduates, and supports PIs whose gender is under-represented in the sciences. Public outreach will include development new materials for the ?I?m College Bound? program. Graduate and undergraduate researchers associated with this project will help develop new geo/earth science demonstrations and coordinate student volunteers. The demonstrations, assignments and lesson plans will be disseminated and published on the "I'm College Bound" web site.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

Rivers are the dynamic link between terrestrial and aquatic ecosystems. The biogeochemical processes that produce, consume, and transform organic carbon in rivers are critical to understanding regional carbon budgets, the controls on river water quality, and ultimately the export of terrestrial organic carbon to coastal regions. Our basic understanding of river carbon cycling is based largely on data from pristine rivers; yet today virtually all rivers are managed to optimize water supply, flood control and hydropower. On the Colorado River a system of dams and reservoirs has dramatically altered hydrodynamics and geomorphology, water residence time, particle load, light conditions, and sediment-water interactions. Comparatively little is known about the effects of these reservoirs on carbon biogeochemistry. This project will assess the distribution, composition and reactivity of terrestrial and riverine carbon along a sequence of well-characterized reservoirs in a single watershed.
This CAREER project integrates hypothesis-driven biogeochemical research questions, state-of-the-art analytical approaches, and innovative teaching strategies to address three fundamental research elements:
1. Developing a regional carbon budget for the Colorado River System using a combination of field measurements and laboratory manipulation experiments.
2. Examining the composition, reactivity, and fate of dissolved and particulate organic carbon in the Colorado River System.
3. Enhancing learning outcomes for geoscience students through field-based teaching.
Longitudinal water sampling, carbon characterization, and biogeochemical process studies, culminating in a carbon budget for each reservoir, will assess the trophic state of the river system and reveal new insights into the interactions among the biological and physico-chemical mechanisms that transform terrestrial and riverine carbon. The research and teaching will be integrated through inquiry-based student field-projects that address discrete questions complementary to the broader scientific objective; the students results will be integrated into classroom activities, enhancing science education for hundreds of other students. This project will provide undergraduate geoscientists the skills to address complex environmental problems by exposing them to field-based research at an early stage in their academic career. The Colorado river system provides a unique opportunity to study a large managed river, and the results of this work will provide insight for the biogeochemical mechanisms that support carbon cycling in contemporary river systems.

This project aims to improve transfer student success at Arizona State University (ASU). A significant problem is that although transfer students make up 33% of entering science majors at ASU, they have lower retention rates, a slower time to graduation, and do not participate as much in undergraduate research as students who begin their college experience at ASU. This project uses a scholarship program to give transfer students access to a set of courses that help support and mentor them in undergraduate research experiences. By focusing on transfer students, the project will broaden the participation of students underrepresented in science at ASU because transfer students are a more diverse student population.

The goal of this project is to integrate transfer students into the high impact practice of scientific research through a scholarship program. Fifty transfer students will progress through four levels of courses that will take them from novice to practicing scientist. These course-supported undergraduate research experiences will provide the structure for a unique research learning community among transfer students in biological sciences, physical sciences, and geosciences and the integration of these transfer students into the established scientific research community. The impact of this program is being measured to determine factors that increase the quality of the experience of transfer students, specifically leading to better research experiences, graduation rates, and entry into the workforce or graduate school. This project will advance understanding of how participation in research can positively impact the experience of transfer students. Further, the curriculum will be packaged for broad dissemination and could be used as a model for other institutions who are interested in engaging transfer students in research.