Reconstructing Nitrogen Cycling and Ecosystem Structure in the Bering Sea through the Anomalously Warm, High- Productivity, Hypoxic Bolling-Allerod Event

Abstract
During the most recent deglaciation, the North Pacific underwent a period of abrupt warming, coinciding with large phytoplankton blooms and hypoxic intermediate water. The cause of this event remains debated; both iron fertilization and dramatic shifts in vertical mixing have been hypothesized. I propose to test these hypotheses and investigate related marine biogeochemical feedbacks using high-resolution, laminated sediments from IODP U1340 in the Bering Sea. I will pair traditional proxies, including foraminifera δ¹⁸O and Mg/Ca and nutrient isotopes, with a novel proxy, compound-specific isotopes of amino acids (CSI-AA), to measure changes in nitrogen cycling and ecosystem structure associated with the shifts in climate regime.

Biography

I love science for the same reason I love art, poetry, and travel: because it opens our eyes to a new perspective with which to understand the world. Currently, I am learning how to see the world through the eyes of polar marine diatoms. I am earning my PhD at the University of California Santa Cruz, where I am working with Christina Ravelo and Matt McCarthy to investigate interactions between marine biogeochemical cycling and the climate system. My current research uses a variety of techniques including foraminifera δ18O, nitrogen and silicon isotopes, and diatom community composition to measure various physical, chemical, and ecological parameters of the ocean-climate system. My previous research at UNC-Chapel Hill and the University of New Hampshire includes marine microbial ecology, diatom physiology, and climate reconstruction. The Schlanger fellowship provides me with the opportunity to apply my multifaceted interests to pursue novel research in paleo-biogeochemistry.

Mineral-associated microbial ecology of the deep subsurface, Nankai Trough, Japan

Abstract
Minerals host the marine subsurface biosphere, but it remains unknown if specific minerals present in marine sediments play a role in facilitating microbial survival in the deep biosphere. Conductive minerals have been shown to stimulate the metabolic activity of microorganisms sampled from the subsurface, suggesting subsurface microorganisms may associate with these phases in situ. I hypothesize that biosynthetically-active microorganisms in the deep biosphere associate with conductive minerals. I propose to test this hypothesis by applying mineral separation techniques to incubations of sediment from IODP Expedition 370 followed by downstream microbial community analysis via iTag sequencing corroborated by fluorescence in situ hybridization (FISH) and evaluation of biosynthetic activity employing bioorthogonal noncanonical amino acid tagging (BONCAT).

Biography

My interest in geobiology and environmental microbiology was first sparked during my undergraduate thesis with Professor Robert Gaines at Pomona College. Through this project, in which I examined dissimilatory reduction of ferric iron bound in clay minerals, I learned to appreciate the dazzling diversity of the microbial world and its profound impact on global biogeochemistry. I sought to further explore the interplay between microbiology and geochemistry through my PhD work with Dr. Victoria Orphan at Caltech, where I’ve applied novel mineral separation techniques to seafloor sediments to parse the microbial ecology of sediments at unprecedented resolution. In my project funded by the Schlanger Fellowship, I will apply these novel techniques to sediments retrieved from the marine deep subsurface on IODP Expedition 370 with the aim of revealing new insight into microbe-mineral and microbe-microbe interactions in the deep biosphere.

Investigating the Piezophilic Microbial Communities of Mariana Forearc Serpentinite Mud Volcanoes

Abstract

Despite the significant impact that high hydrostatic pressure has on deep-sea microbial communities, little is known about the role it plays within the deep subsurface biosphere. This includes the serpentinite mud volcanoes of the Mariana forearc (which characteristically have high pH and high concentrations of methane, hydrogen, formate, and acetate), a possible habitat for the origin of life. This study aims to assess deep subsurface piezophilic (pressure- loving) microbial communities present within the serpentinite mud volcanoes of the Mariana forearc – which were drilled during International Ocean Discovery Program (IODP) Expedition 366. Metagenomics, single-cell genomics, and metatranscriptomics will be employed to determine the community composition of the high-pressure adapted microorganisms present within these systems, as well as their functional potential within this environment. Comparison of metatranscriptomes of replicate microcosms incubated at various pressures will reveal, on a community level, genes important for adaptation to high hydrostatic pressure. This work will shed light on the role pressure plays within the deep biosphere and provide further insight into adaptations to environmental conditions present on the early Earth and which also exist elsewhere in the solar system.

Biography

As an undergraduate at Rutgers University, it was my work on hydrothermal vent microbial communities that sparked my interest in the study of extremophilic microbes. Now pursuing a Ph.D. in Marine Biology at the Scripps Institution of Oceanography, my research focuses on microbial adaptation to extreme environments – particularly high pressure and high pH systems. I utilize coupled molecular and physiological approaches to understand how microbes adapt to survive at the limits of life, and how these adaptations may be relevant to the origin of life on Earth and elsewhere in our solar system. The Schlanger Fellowship allows me to investigate the extremophilic microbial communities in a region hypothesized as a possible location for the origin of life on Earth, the Mariana Forearc serpentinite mud volcanoes.

The role of atmospheric CO₂ in late Miocene environmental change: a multi-proxy study

Abstract
The Late Miocene saw dramatic environmental change and ecosystem revolution. Sea surface temperatures dropped by 5-10°C from 10 to 6 Ma; grasses adapted to arid, low-CO₂ conditions expanded across the tropics and subtropics. Both are potential responses to declining CO₂. However, CO₂ estimates for this time period are limited, and most records suggest little to no change through this transition. Are estimates of CO₂ incorrect and plagued by poor assumptions, or do we not understand the coupling of CO₂ and climate? Here I propose to address this question with new state-of-the-art records from two marine paleo-CO₂ proxies. I will assess the history of atmospheric CO₂ across the Late Miocene through the first multi-proxy, multi-site study.

Biography

Born in Rhode Island and raised in Vermont, I developed an appreciation for the environment at an early age. Between my junior and senior undergraduate years, I carried out a summer research project at the Lamont-Doherty Earth Observatory and gained a passion for  geochemistry and paleoclimate. My dissertation research focuses on reconstructing atmospheric CO2 concentrations over the last ~15 million years using the stable carbon isotope ratios of long-chain alkenones and the mineral remains of coccolithophorid algae. With the Schlanger Fellowship, I will expand on my thesis research by estimating surface ocean pH and atmospheric CO2 using boron isotope ratios of planktic foraminifera from the same sediment samples in which I have alkenone-based CO2 estimates, providing a direct inter-proxy comparison.

Fault healing and shallow slow slip at the Hikurangi subduction margin: The impact of normal stress and loading- rate on friction

Abstract
Observations of a host of slip behaviors at subduction zones around the world, challenging the standard model of discontinuous seismic and aseismic slips, has generated much excitement in the geoscientific community. However, the mechanics of these phenomena is, as yet, poorly understood. The observation of repeating slow slip events at the northern Hikurangi margin suggests a mechanism by which the slipping fault patch is able to regain its strength, or ‘heal’ after a slip event. This is supported by numerical models constrained by geodetic measurements of fault relocking. However, this hypothesis has never been tested on sediments from a slow slip source region. Here, I propose to do so by conducting laboratory experiments on fault zone and subduction input samples acquired during expedition 375 to constrain the frictional regime of shallow slow slip at the northern Hikurangi margin.

Biography

I got my undergraduate degree in geoengineering from the National Institute of Technology Karnataka in India. It was during my masters in rock engineering, at the University of Arizona, that I started to grow a keen interest in geophysics and fault mechanics. At Arizona, I worked on better quantifying stability and failure mechanisms for underground constructions. Through this, I developed an interest in applying similar techniques to probe the frictional mechanisms responsible for earthquakes. Currently, as a graduate student working with Prof. Chris Marone at Penn State, I use a combination of friction experiments and ultrasonic acoustic measurement techniques to constrain the frictional behavior of faults at multiple scales. As part of this work, I hope to better understand the frictional regime of shallow slow earthquakes at the Hikurangi Subduction Margin. This will allow for a better understanding of the underlying mechanisms that govern the mode of failure of seismogenic faults. When I’m not making tiny earthquakes in the lab, I’m usually climbing or baking.