Edwards Bethanie R.

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Edwards
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Bethanie R.
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  • Article
    The multiple fates of sinking particles in the North Atlantic Ocean
    (John Wiley & Sons, 2015-09-25) Collins, James R. ; Edwards, Bethanie R. ; Thamatrakoln, Kimberlee ; Ossolinski, Justin E. ; DiTullio, Giacomo R. ; Bidle, Kay D. ; Doney, Scott C. ; Van Mooy, Benjamin A. S.
    The direct respiration of sinking organic matter by attached bacteria is often invoked as the dominant sink for settling particles in the mesopelagic ocean. However, other processes, such as enzymatic solubilization and mechanical disaggregation, also contribute to particle flux attenuation by transferring organic matter to the water column. Here we use observations from the North Atlantic Ocean, coupled to sensitivity analyses of a simple model, to assess the relative importance of particle-attached microbial respiration compared to the other processes that can degrade sinking particles. The observed carbon fluxes, bacterial production rates, and respiration by water column and particle-attached microbial communities each spanned more than an order of magnitude. Rates of substrate-specific respiration on sinking particle material ranged from 0.007 ± 0.003 to 0.173 ± 0.105 day−1. A comparison of these substrate-specific respiration rates with model results suggested sinking particle material was transferred to the water column by various biological and mechanical processes nearly 3.5 times as fast as it was directly respired. This finding, coupled with strong metabolic demand imposed by measurements of water column respiration (729.3 ± 266.0 mg C m−2 d−1, on average, over the 50 to 150 m depth interval), suggested a large fraction of the organic matter evolved from sinking particles ultimately met its fate through subsequent remineralization in the water column. At three sites, we also measured very low bacterial growth efficiencies and large discrepancies between depth-integrated mesopelagic respiration and carbon inputs.
  • Article
    LOBSTAHS : an adduct-based lipidomics strategy for discovery and identification of oxidative stress biomarkers
    (American Chemical Society, 2016-06-20) Collins, James R. ; Edwards, Bethanie R. ; Fredricks, Helen F. ; Van Mooy, Benjamin A. S.
    Discovery and identification of molecular biomarkers in large LC/MS data sets requires significant automation without loss of accuracy in the compound screening and annotation process. Here, we describe a lipidomics workflow and open-source software package for high-throughput annotation and putative identification of lipid, oxidized lipid, and oxylipin biomarkers in high-mass-accuracy HPLC-MS data. Lipid and oxylipin biomarker screening through adduct hierarchy sequences, or LOBSTAHS, uses orthogonal screening criteria based on adduct ion formation patterns and other properties to identify thousands of compounds while providing the user with a confidence score for each assignment. Assignments are made from one of two customizable databases; the default databases contain 14 068 unique entries. To demonstrate the software’s functionality, we screened more than 340 000 mass spectral features from an experiment in which hydrogen peroxide was used to induce oxidative stress in the marine diatom Phaeodactylum tricornutum. LOBSTAHS putatively identified 1969 unique parent compounds in 21 869 features that survived the multistage screening process. While P. tricornutum maintained more than 92% of its core lipidome under oxidative stress, patterns in biomarker distribution and abundance indicated remodeling was both subtle and pervasive. Treatment with 150 μM H2O2 promoted statistically significant carbon-chain elongation across lipid classes, with the strongest elongation accompanying oxidation in moieties of monogalactosyldiacylglycerol, a lipid typically localized to the chloroplast. Oxidative stress also induced a pronounced reallocation of lipidome peak area to triacylglycerols. LOBSTAHS can be used with environmental or experimental data from a variety of systems and is freely available at https://github.com/vanmooylipidomics/LOBSTAHS.
  • Thesis
    The biogeochemistry of lipid derived infochemical signals in the ocean
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-02) Edwards, Bethanie R.
    The role of oxylipins in ocean biogeochemistry was investigated using microcosm amendment experiments, environmental lipidomics, and culture based studies. Oxylipins are a bioactive class of secondary metabolites produced by diatoms and other eukaryotic phytoplankton. Previous research has focused mainly on one class of oxylipins, polyunsaturated aldehydes (PUAs), and their impacts on copepods. And few studies have looked at the impacts of oxylipins in situ. Here I show that oxylipins have the potential to impact carbon flux attenuation, oxylipin production in situ is linked to diatom bloom decline and viruses, and oxylipins deter microzooplankton grazing. Sinking particles collected in the North Atlantic were determined to be hot spots for PUAs with concentrations in the micromolar range. Natural particle associated microbial communities exhibited a dose dependent response to PUAs. Stimulatory PUA concentrations ranged from 1-10 μM, resulting in enhanced remineralization of organic matter by particle associated microbes. Thus, PUAs produced during bloom decline may lead to greater flux attenuation and nutrient recycling. A novel lipidomics approach was applied along a cruise track in the California Coastal System revealing that canonical diatom free fatty acids and oxylipins dominated the dissolved lipidome and oxylipin abundance was correlated with diatom bloom demise as assessed by phaeophytin and biogenic Si. RNA viruses were likely the cause of diatom bloom demise and may have induced oxylipin production. The link between viruses and oxylipins represents a new infochemical signaling pathway in the ocean. Many oxylipins that are novel to the marine environment were also identified. The dissolved lipidome was sampled during grazing experiments with the microzooplankton grazer Oxyrrhis marina and both wild type Phaeodactylum tricornutum and a chronically stressed, transgenic strain (PtNOA). Grazing was suppressed in the PtNOA treatments compared to the WT, likely due to upregulation of small unknown lipophilic molecules. This suggests that cellular stress and oxylipin production may deter microzooplankton grazing in the environment potentially altering the transfer of energy through the microbial food web. By employing interdisciplinary approaches, we have learned that oxylipins production in situ is linked to bloom decline and the bioactivity of these compounds has significant implications for ocean biogeochemical cycles.
  • Article
    Building an inclusive wave in marine science: Sense of belonging and Society for Women in Marine Science symposia
    (Elsevier, 2023-08-30) Canfield, Katherine Nicole ; Sterling, Alexa R. ; Hernandez, Christina M. ; Chu, Sophie N. ; Edwards, Bethanie R. ; Fontaine, Diana N. ; Freese, Jillian M. ; Giroux, Marissa S. ; Jones, Aubree E. ; McCarty, Alexandra J. ; Morrissette, Hannah K. ; Palevsky, Hilary I. ; Raker, Catherine E. ; Robuck, Anna R. ; Serrato-Marks, Gabriela ; Thibodeau, Patricia S. ; Windle, Anna E.
    Achieving gender equity is a long-standing and ubiquitous challenge in marine science. Creating equitable experiences for all genders in marine science requires recognizing scientists’ intersectional identities, and how this leads to unique lived experiences of privilege and marginalization. One approach to increase equitable experiences for women in marine science is to create affinity groups where women can learn from each other, share their experiences, and provide support and mentorship. The Society for Women in Marine Science (SWMS) is one such organization, founded to amplify the work of early career women in marine science and create community, through events such as full-day symposium events. This study investigates the experiences of symposium attendees for four events held from 2018 through 2020, as reported in pre- and post-symposium surveys. We used quantitative analysis of the open-ended survey questions to examine the demographics of attendees and their fields of study. Qualitative thematic analysis identified the most effective aspects of the symposia, areas of logistical and content improvement for future symposia, and emphasized the unique challenges women in marine science experience. The majority of symposium attendees were white graduate students. Nearly all attendees identified as women, with a small number of men and non-binary individuals. Symposia attendees enjoyed opportunities for professional development and interactions with colleagues across career stages. We present recommendations for continuing to foster a sense of belonging in marine science and STEM more broadly, both specific to SWMS and transferable actions that can be applied for other affinity groups. These suggestions include empathetic event logistics, continual democratic evaluation, identity reflexivity among group leaders, and professional development activities targeted towards the unique needs of the affinity group. The positive responses received from SWMS’s adaptive integration of survey results into symposia demonstrate that incorporating these recommendations and findings will help create an inclusive wave in marine science.
  • Article
    Viral infection leads to a unique suite of allelopathic chemical signals in three diatom host-virus pairs
    (MDPI, 2024-05-17) Edwards, Bethanie R. ; Thamatrakoln, Kimberlee ; Fredricks, Helen F. ; Bidle, Kay D. ; Van Mooy, Benjamin A. S.
    Ecophysiological stress and the grazing of diatoms are known to elicit the production of chemical defense compounds called oxylipins, which are toxic to a wide range of marine organisms. Here we show that (1) the viral infection and lysis of diatoms resulted in oxylipin production; (2) the suite of compounds produced depended on the diatom host and the infecting virus; and (3) the virus-mediated oxylipidome was distinct, in both magnitude and diversity, from oxylipins produced due to stress associated with the growth phase. We used high-resolution accurate-mass mass spectrometry to observe changes in the dissolved lipidome of diatom cells infected with viruses over 3 to 4 days, compared to diatom cells in exponential, stationary, and decline phases of growth. Three host virus pairs were used as model systems: Chaetoceros tenuissimus infected with CtenDNAV; C. tenuissimus infected with CtenRNAV; and Chaetoceros socialis infected with CsfrRNAV. Several of the compounds that were significantly overproduced during viral infection are known to decrease the reproductive success of copepods and interfere with microzooplankton grazing. Specifically, oxylipins associated with allelopathy towards zooplankton from the 6-, 9-, 11-, and 15-lipogenase (LOX) pathways were significantly more abundant during viral lysis. 9-hydroperoxy hexadecatetraenoic acid was identified as the strongest biomarker for the infection of Chaetoceros diatoms. C. tenuissimus produced longer, more oxidized oxylipins when lysed by CtenRNAV compared to CtenDNAV. However, CtenDNAV caused a more statistically significant response in the lipidome, producing more oxylipins from known diatom LOX pathways than CtenRNAV. A smaller set of compounds was significantly more abundant in stationary and declining C. tenuissimus and C. socialis controls. Two allelopathic oxylipins in the 15-LOX pathway and essential fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were more abundant in the stationary phase than during the lysis of C. socialis. The host–virus pair comparisons underscore the species-level differences in oxylipin production and the value of screening more host–virus systems. We propose that the viral infection of diatoms elicits chemical defense via oxylipins which deters grazing with downstream trophic and biogeochemical effects.