Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sutherland, K. M., Wankel, S. D., & Hansel, C. M. Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen. Proceedings of the National Academy of Sciences of the United States of America, 117(7), (2020): 3433-3439, doi:10.1073/pnas.1912313117.The balance between sources and sinks of molecular oxygen in the oceans has greatly impacted the composition of Earth’s atmosphere since the evolution of oxygenic photosynthesis, thereby exerting key influence on Earth’s climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine oxygen budget include photosynthesis, respiration, photorespiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic oxygen cycling, namely the ubiquitous one-electron reduction of O2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross oxygen sink comprising about a third of marine gross oxygen production, and a net oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive oxygen species and a complex and dynamic oxygen cycle in which oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine oxygen cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.This work was supported by NASA Earth and Space Science Fellowship NNX15AR62H to K.M.S., NASA Exobiology grant NNX15AM04G to S.D.W. and C.M.H., and NSF Division of Ocean Sciences grant 1355720 to C.M.H. This research was further supported in part by Hanse-Wissenschaftskolleg Institute of Advanced Study fellowships to C.M.H. and S.D.W. We thank Danielle Hicks for assistance with figures and Community Earth Systems Model (CESM) Large Ensemble Project for the availability and use of its data product. The CESM project is primarily supported by the NSF

Conservation status of New Zealand freshwater invertebrates, 2013

The conservation status of 644 freshwater invertebrate taxa, across five Phyla, 28 Orders and 75 Families, was assessed using the New Zealand Threat Classification System (NZTCS) criteria. Forty-six species were ranked Nationally Critical, 11 Nationally Endangered and 16 Nationally Vulnerable. One hundred and seventy-two taxa were listed as Data Deficient. A full list is presented, along with summaries and brief notes on the most important changes. This list replaces all previous NZTCS lists for freshwater invertebrates

Investigating Factors Associated with Low Achievement Early in School: A Pilot Study

The purpose of the current study were to (a) examine the relationship between academic achievement and social competence in a sample of kindergarten and first grade students, and (b) investigate the interventions their teachers are using with low achieving students. Sixty kindergarten and first grade students and 15 teachers participated in this study. Results indicated significant differences between low achieving and typically achieving students on reading achievement and teacher reported academic competence. No other significant difference between groups were found. Teachers reported that they most often use explicit instruction with low achieving students; evidence-based practices such as data-based decision making the peer tutoring were not reported as being primary instructional practices. Limitations of the current study and implications for practice are discussed

New insights into the marine oxygen cycle from manganese oxide minerals and reactive oxygen species

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Oceanography and Applied Ocean Science and Engineering at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2020.The redox cycling of oxygen between O2, water, and intermediate redox states including hydrogen peroxide and superoxide, has profound impact on the availability and distribution of dissolved O2, the habitability of the marine biosphere, and cellular metabolic and physiological reactions that utilize O2. The sum total of processes that produce, consume, and exchange atoms with O2 in the atmosphere, oceans, and subsurface leave their isotopic fingerprints on the abundance of the three stable isotopes of O2 in the environment. In this thesis, I explore two aspects of the oxygen cycle in the past and present. First, I investigate the ability of manganese (Mn) oxide minerals to capture and retain the oxygen isotopic signature of dissolved O2 during the oxidation of aqueous Mn(II) to Mn-oxide minerals. I determine that approximately half of the oxygen atoms in Mn(III,IV) oxides are directly incorporated from dissolved oxygen, and use isotope labeling techniques to further constrain how the dissolved oxygen isotope signature may be determined from that of Mn oxides. I perform an in-depth characterization of a ferromanganese crust from the central Pacific and, using triple oxygen isotope measurements, demonstrate that Mn oxides in ferromanganese crusts from around the world retain signatures of dissolved oxygen for at least 30 million years. I next turn to a previously unconsidered aspect of the global oxygen cycle: dark, extracellular superoxide production by marine microbes. I measure extracellular superoxide production rates by some of the ocean’s most abundant organisms. I use these rates along with previous measurements to estimate that extracellular superoxide production yields a net sink of 5-19% of marine dissolved oxygen. Ultimately, the degree to which superoxide production is a sink of oxygen lies in the fate of its primary decay product, hydrogen peroxide. I determine the range of oxidative and reductive decay of hydrogen peroxide across a range of environmental conditions in a meromictic pond, thus validating several assumptions from our global estimate. Altogether, this thesis illuminates a path toward investigating the oxygen cycle on million-year timescales in Earth’s recent past and demonstrates the importance of microbial superoxide production in the biogeochemical cycling of O2.This work was funded by the following grants and organizations: NASA Earth and Space Science Fellowship (NNX15AR62H), MIT Praecis Presidential Graduate Fellowship, NASA Exobiology (NNX15AM046), NSF-OCE grant 1355720, WHOI Ocean Ventures Fund, MIT Student Assistance Fund, WHOI Academic Programs Office, and the Stanford Synchrotron Radiation Lightsource. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DEAC02-76SF00515

The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

Over the last ten years, photonic band gap (PBG) theory and technology have become an important area of research because of the numerous possible applications ranging from high-efficiency laser diodes to optical circuitry. This research concentrates on reducing the length scale in the fabrication of layered photonic band gap structures and developing procedures to improve processing consistency. Various procedures and materials have been used in the fabrication of layered PBG structures. This research focused on an economical micro transfer molding approach to create the final PBG structure. A poly dimethylsiloxane (PDMS) rubber mold was created from a silicon substrate. It was filled with epoxy and built layer-by-layer to create a 3-D epoxy structure. This structure was infiltrated with nanoparticle titania or a titania sol-gel, then fired to remove the polymer mold, leaving a monolithic ceramic inverse of the epoxy structure. The final result was a lattice of titania rolds that resembles a face-centered tetragonal structure. The original intent of this research was to miniaturize this process to a bar size small enough to create a photonic band gap for wavelengths of visible electro-magnetic radiation. The factor limiting progress was the absence of a silicon master mold of small enough dimensions. The Iowa State Microelectronics Research Center fabricated samples with periodicities of 2.5 and 1.0 microns with the existing technology, but a sample was needed on the order of 0.3 microns or less. A 0.4 micron sample was received from Sandia National Laboratory, which was made through an electron beam lithography process, but it contained several defects. The results of the work are primarily from the 2.5 and 1.0 micron samples. Most of the work focused on changing processing variables in order to optimize the infiltration procedure for the best results. Several critical parameters were identified, ranging from the ambient conditions to the specifics of the procedure. It is believed that most critical for fabrication of high quality samples is control of the temperature of the sample during and after infiltration, and the rate and amount of time spent applying epoxy to the PDMS

Cross-Cultural Perspectives After Participation in the YES Program: A Pilot Study

Abstract:  Guided by empowerment and ecological theories, the Youth Empowerment Solutions (YES) program facilitates character development through activities based in cultural differences, team building, and social change. This pilot study consisted of two focus groups (n = 13) of middle school youth conducted after their participation in an abbreviated version of the YES program. Specifically, the present study examined youth’s cross-cultural perspectives after participation. The focus groups were transcribed and coded for emergent themes using Heaton’s (2005) supplementary data analysis framework. Qualitative analysis resulted in two emergent themes: 1) enhanced appreciation for similarities and differences in cultural and ethnic backgrounds, and 2) the role of respect in understanding differences and confronting stereotypes. Specifically, youth reported that engagement in this program fostered positive awareness of cultural differences and respect for inter-ethnic relationships. The findings provide support for the benefits of the YES program on moral development and promotion of healthy peer relationships

Cross-Cultural Perspectives After Participation in the YES Program: A Pilot Study

Guided by empowerment and ecological theories, the Youth Empowerment Solutions (YES) program facilitates character development through activities based in cultural differences, team building, and social change. This pilot study consisted of two focus groups (n = 13) of middle school youth conducted after their participation in an abbreviated version of the YES program. Specifically, the present study examined youth’s cross-cultural perspectives after participation. The focus groups were transcribed and coded for emergent themes using Heaton’s (2005) supplementary data analysis framework. Qualitative analysis resulted in two emergent themes: 1) enhanced appreciation for similarities and differences in cultural and ethnic backgrounds, and 2) the role of respect in understanding differences and confronting stereotypes. Specifically, youth reported that engagement in this program fostered positive awareness of cultural differences and respect for inter-ethnic relationships. The findings provide support for the benefits of the YES program on moral development and promotion of healthy peer relationships

Constructing “Packages” of Evidence-Based Programs to Prevent Youth Violence: Processes and Illustrative Examples From the CDC’s Youth Violence Prevention Centers

This paper describes the strategic efforts of six National Centers of Excellence in Youth Violence Prevention (YVPC), funded by the U.S. Centers for Disease Control and Prevention, to work in partnership with local communities to create comprehensive evidence-based program packages to prevent youth violence. Key components of a comprehensive evidence-based approach are defined and examples are provided from a variety of community settings (rural and urban) across the nation that illustrate attempts to respond to the unique needs of the communities while maintaining a focus on evidence-based programming and practices. At each YVPC site, the process of selecting prevention and intervention programs addressed the following factors: (1) community capacity, (2) researcher and community roles in selecting programs, (3) use of data in decision-making related to program selection, and (4) reach, resources, and dosage. We describe systemic barriers to these efforts, lessons learned, and opportunities for policy and practice. Although adopting an evidence-based comprehensive approach requires significant upfront resources and investment, it offers great potential for preventing youth violence and promoting the successful development of children, families and communities

Research-Based Practices as a Protective Factor for Students At-Risk for Academic Failure

Increasing pressure on teachers and administrators due to high-stakes testing has led to increased risk to our most vulnerable population, those students who arrive at school without the prerequisite skills necessary to successfully participate in the academic climate of the classroom. Unfortunately, given the large range of ability levels often present even in early elementary school, teachers face enormous challenges in meeting the needs of all their students. Further, due to the challenges inherent in teaching low-achieving students, and the ensuing classroom behavior problems often presented by these students, teachers may be conditioned to avoid interacting with these students, particularly during academic instruction. Accumulated over time this differential treatment adds another risk factor that may contribute to students’ negative developmental outcomes. The purpose of this paper is to review the literature on academic interventions for low achieving elementary students that might serve to remedy early learning problems in the classroom, thereby setting the stage for improved academic and social competence manifested by desired teacher and peer relationships predictive of school success

Spectroscopic insights into ferromanganese crust formation and diagenesis

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 21(11), (2020): e2020GC009074, doi:10.1029/2020GC009074.Marine ferromanganese deposits, often called the scavengers of the sea, adsorb and coprecipitate with a wide range of metals of great interest for paleo‐environmental reconstructions and economic geology. The long (up to ∼75 Ma), near‐continuous record of seawater chemistry afforded by ferromanganese deposits offers much historical information about the global ocean and surface earth including crustal processes, mantle processes, ocean circulation, and biogeochemical cycles. The extent to which the ferromanganese deposits hosting these geochemical proxies undergo diagenesis on the seafloor, however, remains an important and challenging factor in assessing the fidelity of such records. In this study, we employ multiple X‐ray techniques including micro–X‐ray fluorescence, bulk and micro–X‐ray absorption spectroscopy, and X‐ray powder diffraction to probe the structural, compositional, redox, and mineral changes within a single ferromanganese crust. These techniques illuminate a complex two‐dimensional structure characterized by crust growth controlled by the availability of manganese (Mn), a dynamic range in Mn oxidation state from +3.4 to +4.0, changes in Mn mineralogy over time, and recrystallization in the lower phosphatized portions of the crust. Iron (Fe) similarly demonstrates spatial complexity with respect to concentration and mineralogy, but lacks the dynamic range of oxidation state seen for Mn. Micrometer‐scale measurements of metal abundances reveal complex element associations between trace elements and the two major oxide phases, which are not typically resolvable via bulk analytical methods. These findings provide evidence of post‐depositional processes altering chemistry and mineralogy, and provide important geochemical context for the interpretation of element and isotopic records in ferromanganese crusts.This research is supported by NASA Exobiology NNX15AM046 to Scott D. Wankel and Colleen M. Hansel, NASA NESSF NNX15AR62H to Kevin M. Sutherland, and WHOI Ocean Exploration Institute to Colleen M. Hansel. The Stanford Synchrotron Radiation Lightsource was utilized in this study. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE‐AC02‐76SF00515.2021-04-2