Minor Elizabeth C.

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Minor
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Elizabeth C.
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Now showing 1 - 5 of 5
  • Preprint
    Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analyses
    ( 2017-03) Zigah, Prosper ; Minor, Elizabeth C. ; McNichol, Ann P. ; Xu, Li ; Werne, Josef P.
    We measured the concentrations and isotopic compositions of solid phase extracted (SPE) dissolved organic carbon (DOC) and high molecular weight (HMW) DOC and their constituent organic components in order to better constrain the sources and cycling of DOC in a large oligotrophic lacustrine system (Lake Superior, North America). SPE DOC constituted a significant proportion (41-71 %) of the lake DOC relative to HMW DOC (10-13%). Substantial contribution of 14C-depleted components to both SPE DOC (Δ14C = 25 to 43‰) and HMW DOC (Δ14C = 22 to 32‰) was evident during spring mixing, and depressed their radiocarbon values relative to the lake dissolved inorganic carbon (DIC; Δ14C ~ 59‰). There was preferential removal of 14C-depleted (older) and thermally recalcitrant components from HMW DOC and SPE DOC in the summer. Contemporary photoautotrophic addition to HMW DOC was observed during summer stratification in contrast to SPE DOC, which decreased in concentration during stratification. Serial thermal oxidation radiocarbon analysis revealed a diversity of sources (both contemporary and older) within the SPE DOC, and also showed distinct components within the HMW DOC. The thermally labile components of HMW DOC were 14C-enriched and are attributed to heteropolysaccharides (HPS), peptides/amide and amino sugars (AMS) relative to the thermally recalcitrant components reflecting the presence of older material, perhaps carboxylic-rich alicyclic molecules (CRAM). The solvent extractable lipid-like fraction of HMW DOC was very 14C-depleted (as old as 1270-2320 14C years) relative to the carbohydrate-like and protein-like substances isolated by acid hydrolysis of HMW DOC. Our data constrain relative influences of contemporary DOC and old DOC, and DOC cycling in a modern freshwater ecosystem.
  • Thesis
    Compositional heterogeneity within oceanic POM : a study using flow cytometry and mass spectrometry
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998-03) Minor, Elizabeth C.
    This thesis applied direct temperature-resolved mass spectrometry (DT-MS), flow cytometry, and multivariate statistics to the study of marine particulate organic matter (POM) collected from the North Atlantic. DT-MS is an important asset to marine organic geochemistry as a single two minute analysis (with 16 eV, EI+ ionization) provides information on polysaccharides, proteins, and lipids within concentrated and desalted samples. Although the molecularlevel information obtained with DT -MS is less detailed than traditional analyses of specific compound classes, DT-MS can act as a useful molecular-level screening technique (as illustrated in this thesis), indicating what samples and compound classes to investigate more thoroughly. In addition to its rapidity, DT-MS only reqires microgram quantities of sample. This sensitivity permits t..l-J.e coupling of DT -MS and preporative flow cytometry. In this thesis, preparative flow cytometry was used to isolate "phytoplankton" and "detritus" (i.e., non-phytoplankton particles) in 2~53 !liD POM. The molecular-level differences between and within small-particle POM (<53 !liD), large-particle POM (>53 !liD), "phytoplankton" and "detritus" were explored using DT -MS and discriminant analysis. For POM collected from the Mid-Atlantic Bight and from Great Harbor, Woods Hole, MA, small-particle POM contained more phytoplankton chemical characteristics than large-particle POM. In Great Harbor, the molecular-level characteristics of large-particle POM indicated a significant grazer biomass component. On the MAB (in March 1996), the large-particle POM appeared more phytodetrital. "Phytoplankton" was enriched in protein, chlorophyll and lipids as compared to "detritus," which was enriched in selected polysaccharides. As the polysaccharide composition of POM subclasses was a major source of variation, polysaccharides in selected samples were further studied using ammonia and deuterated ammonia CI+ DT-MS. Principal component analysis of the resulting NH3-CI+ spectra indicated that the majority of polysaccharide variation in the selected samples could be explained by a component that appeared related to the degree of degradation of the organic matter. The results from this thesis, coupled with existing work on particulate and dissolved organic matter, were used to support a modified "size-reactivity continuum model" of organic matter cycling.
  • Dataset
    CTD profiles, down/up casts from R/V Blue Heron cruises BH09-05, BH09-12, BH10-14, BH10-03 on Lake Superior; 2009-2010 (Lake Superior Radiocarbon project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-10-29) Minor, Elizabeth C. ; Werne, Josef P.
    CTD profiles, down/up casts from R/V Blue Heron cruises BH09-05, BH09-12, BH10-14, BH10-03 on Lake Superior; 2009-2010. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/3911
  • Dataset
    Radiocarbon data from R/V Blue Heron cruise BH10-14 on Lake Superior in August 2010 (Lake Superior Radiocarbon project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-10-31) Minor, Elizabeth C. ; Werne, Josef P.
    Radiocarbon data from R/V Blue Heron cruise BH10-14 on Lake Superior in August 2010. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/3920
  • Preprint
    Characterization of dissolved organic matter in Lake Superior and its watershed using ultrahigh resolution mass spectrometry
    ( 2011-11-14) Minor, Elizabeth C. ; Steinbring, Carla J. ; Longnecker, Krista ; Kujawinski, Elizabeth B.
    With the advent of ultrahigh resolution mass spectrometry, recent studies have begun to resolve molecular-level relationships between terrestrial and aquatic dissolved organic matter (DOM) in rivers, estuaries, mangrove swamps and their receiving oceans and lakes. Here, we extend ultrahigh resolution mass spectrometry techniques to Lake Superior, the largest freshwater lake in the world by area. Solid-phase extracted samples from the western arm of the lake and its watershed, including swamp, creek, river, lake-river confluence and offshore lake sites were compared using electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Results were analyzed using cluster analysis and van Krevelen diagrams. Chemical similarity appears related to hydrological proximity, terrestrial impact and flow conditions. For example, higher and lower flow samples from the same stream differ from one another. Toivola Swamp, Lake Superior, and the south shore river have diverse arrays of unique molecular formulae.relative to the north shore river and stream sampled in this data set. Lake Superior’s unique elemental formulae, relative to its watershed samples, are primarily in the lignin-like and reduced hydrocarbon regions of van Krevelen diagrams. ESI-amenable Lake Superior DOM also has a higher proportion of formulae containing nitrogen or sulfur relative to the other samples. The degree of overlap among formulae within our data set is consistent with previous ESI FT-ICR-MS characterization of terrestrial, estuarine and marine OM. There appears to be a conserved portion of formulae across natural OM samples, perhaps because these compounds are intrinsically refractory or because they are commonly generated as products of natural reworking processes.